Strabismus.

Strabismus Eugene

M.

Helveston, MD

three years a new reviewer the task of compiling and presenting in capsule form the important literature of the world dealing with the subject of strabis¬ mus.' This task becomes one of selec¬ tion and, therefore, omission because of the large number of published pa¬ pers pertaining to strabismus and strabismus-related entities. This re¬ view also must for reasons of space, availability of material, language barriers, and pure oversight omit cer¬ tain communications that may be in¬ deed worthy of inclusion. It is hoped that what is included is worthy and useful, and apologies are extended to those authors whose works are not cited. This year's review attempts to cover papers that are primarily of a clinical nature. New concepts that have a ready application to the clini¬ cal aspects of strabismus, amblyopia, and related subjects will be stressed. It is hoped that perusal of the con¬ tents of this review along with com¬ plete reading of cited papers that pique the curiosity will enable the reader to keep abreast of the impor¬ tant advances in the field of stra¬ bismus.

Each

assumes

Submitted for publication Jan 27, 1975. From the Department of Ophthalmology, Indiana University Medical Center, Indianapolis, Ind. Reprints not available.

MEETINGS

The Third

Cambridge Ophthalmo¬ logical Symposium was dedicated to

the subject of strabismus. In the words of its chairman, T. Keith Lyle, the aim of the meeting was ". to bring together some of those cur¬ rently engaged in laboratory research into problems of strabismus and clini¬ cians concerned with its treatment _" The meeting, which was held at the beginning of September in 1973, seemed to accomplish the goals of its chairman, and the fruits of this meet¬ ing are preserved for all to benefit from in a single issue of the British Journal of Ophthalmology.2 This type of publication seems a fitting way to preserve efforts that otherwise would be available to only an invited few. In May of 1974, the International Stra¬ bismological Association (ISA) held its second meeting immediately prior to the World Congress of Ophthalmol¬ ogy, which was held in Paris. The ISA meeting took place on a ship that un¬ fortunately was beset by heavy seas. According to participants, seasick¬ ness detracted from the scientific if not the social aspects of the program. The American Association of Certi¬ fied Orthoptists (AACO) has contin¬ ued to hold its annual "Sunday night symposium" in joint sponsorship with the American Academy of Ophthal¬ mology and Otolaryngology (AAOO). The 1972 symposium dealt with nys.

.

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tagmus, the 1973 meeting took

an

in-

depth look at the superior oblique, and the 1974 symposium was titled "Strabismus Plus." The attendance at this meeting, which takes place be¬ tween 8 and 10 pm on the first Sunday of the academy meeting, grows stead¬ ily each year, and by unofficial count reached nearly 1,000 in 1974. This

symposium is open to all academy goers and is worthwhile for anyone even remotely interested in strabis¬ mus. The proceedings of this sympo¬ sium plus 10 to 14 other articles on the

subject of strabismus are published each spring in the American Orthop¬ tic Journal. This journal is available at no cost to any academy member who requests it. Others may obtain the journal for a modest cost. Those interested should inquire in writing to the AAOO office, 15 Second St SW, Rochester, MN 55901. The Third International Orthoptic Congress was held in Boston, Mass, July 1 through 3, 1975. An inter¬ national array of speakers discussed the following topics: the development of binocular vision, amblyopia, nys¬ tagmus, small angle strabismus ap¬ plications of electrodiagnosis, dys¬ thyroid ophthalmoplegia, squint in handicapped children, orthoptic diag¬

nosis and therapy, ocular palsies, sur¬ gery of squint and divergent squint. Proceedings of the congress will be published in book form as they have

in the past. In March of 1974, the American Association for Pediatrie Ophthalmol¬ ogy had its founding meeting in Los Angeles, Calif. A substantial portion of that meeting, as well as the second annual meeting held in February 1975 at Lake Tahoe, Nev, dealt with strabismus or strabismus—related

topics.

As the number of postgraduate meetings dedicated entirely or in part to strabismus reaches spiraling heights, it becomes impossible to list

them all. Suffice it to say, anyone in¬ terested in attending a meeting to "brush up on strabismus" will be able to find one or more meetings not too far from home if he watches the jour¬ nal announcements and reads his mail for solicitations. Books

Two of the important books on stra¬ bismus recently published are volume six of System of Ophthalmology titled Ocular Motility and Strabismus by Sir Stewart Duke-Elder and Kenneth Wybara and Burian and von Noorden's Binocular Vision and Ocular Motility: Theory and Management of Strabismus.' The joy of seeing the latter book published is dulled by the sadness caused by Dr. Burian's death on Nov 24, 1974. Other books of inter¬ est include yet another Atlas of Stra¬ bismus Surgery,* an exhaustive anal¬ ysis of the corneal light reflex," and a paperbound updated version of the original Scobee volume, which has been a standard primer on strabismus for parents of strabismic children or other interested lay persons.7 A de¬ tailed analysis of one man's experi¬ ence with early surgery for congeni¬ tal esotropia by Daniel Taylor, MD, makes interesting reading.8 Two other volumes deal with supranuclear disorders8 and diplopia,1" with the lat¬ ter

actually being

strabismus text.

a

comprehensive

BASIC SCIENCE and Physiology

Anatomy

Extensive studies of iatrogenically visually deprived and iatrogenically strabismic monkeys have been car¬ ried out.1113 The following conclusions were

reached:

Experimental amblyopia can be produced in monkeys, and this ambly¬ opia can be verified in behavioral studies in which the specially trained monkeys were subjected to visual acuity testing. 2. An age of susceptibility to am¬ blyopia exists, and it is a younger age in monkeys than in humans. 3. Physical changes occur in mon¬ keys who have either strabismic or form-deprivation amblyopia, and these changes have been found only in the lateral geniculate body. 1.

4. Fewer cells in the cerebral cor¬ (area 17 and 18) can be driven by the amblyopic eye, and fewer cells can be driven binocularly in monkeys that have strabismus with or without amblyopia. Such visually deprived and strabismically amblyopic mon¬ keys displayed reduced activity at the single neuron level after stimulation of the amblyopic eye. Irreversible amblyopia was pro¬ duced in immature rhesus monkeys whose lids were sutured between birth and nine weeks of age, and also in animals made esotropie during the first week of life. Amblyopia was not produced in monkeys in which exo¬ tropia was induced, nor did it occur with lid closure after 12 weeks of age in monkeys. During the age of sus¬ ceptibility, brief periods of lid closure (two to four weeks) caused severe amblyopia. Clinical studies and expe¬ rience in dealing with patients indi¬ cate that humans who are deprived of visual stimulation at a very young age also develop irreversible ambly¬ opia. Strabismus in early life in hu¬ mans similarly may produce severe amblyopia. However, the age of sus¬ ceptibility in humans is certainly longer than in monkeys, but just how long is not known. Only indirect evidence shows that early realignment of strabismic eyes may lead to more normalized binocu¬ lar cooperation. Clinical studies of early surgery done in esotropie hu¬ mans have not been as convincing of producing improved binocularity with bifoveal fusion as have studies that early strabismus causes reduced bi¬ nocularity. It would seem that care¬ fully controlled, prospective studies carried out at least until subjects tex


have reached visual maturity and can cooperate for testing are required be¬ fore the final answer regarding the effectiveness of early surgery in pro¬ ducing otherwise unattainable bi¬ nocularity is known. It is well known that Siamese cats frequently have crossed eyes.14 A white tiger now in a Chicago zoo has also been observed to have crossed eyes. The Siamese cats were noted to have abnormal lateral geniculate bodies characterized by the presence of fewer uncrossed fibers; that is, some or all of the temporal fibers seemed to cross rather than remain¬ ing uncrossed. This was referred to by the authors as "scrambled input" and was accompanied by suppression leading to a reduced nasal visual field under monocular conditions. The name given to this was the "Midwestern" response. Researchers in the East found a reorganization of the projec¬ tion of the abnormal lateral genic¬ ulate body, and this was termed the "Boston" response. This latter re¬ sponse, with its apparent change in relative localization, is more akin to what has been called in humans "anomalous retinal correspondence." In the works of the author, the relationship of albinism and abnormal visual pathways is an intriguing one and affords a unique opportunity to study and determine the extent to which central pathways can adapt to deal with abnormal patterns of cerebral activity.

Utilizing histochemical techniques, three types of fibers were found in the baboon's extraocular muscle.15 It was suggested that their differences are related to the times of recruit¬ ment of motor units to which they be¬ long. It was pointed out that other workers have demonstrated only two types of fibers, fast and slow. The be¬ havior of extraocular muscles related to the types of fibers that exist and the importance and behavior of each seems to be a fruitful area of study. Accommodation and Accommodative Convergence A concise review of laboratory con¬ tributions to strabismus includes an especially useful review of the accom¬ modative convergence-accommoda¬ tion (AC/A) ratio.16 Response AC/A

is

laboratory measurement utilizing objective refracting device or optometer. The amount or degree of convergence the subject produces can a

an

be measured relative to the exact amount of accommodation carried out by the subject. This determines the true AC/A under the conditions tested. Such tests proved useful to de¬ termine that anticholinesterase drugs are more effective with a high AC/A and less effective with a low AC/A. Anticholinesterase drugs are there¬ fore less effective in reducing esodeviations with a low response AC/A. Other methods of determining the AC/A are the distance-near heterophoria comparison, and the stimulus (gradient or lenticular) method. The comparison of the distance-near rela¬ tionship, divided by the accom¬ modation requirement of the near point added to the pupillary distance (expressed in centimeters) gives a number for the AC/A, but this is sub¬ ject to built-in errors related to un¬ known factors associated with near¬ ness.

A more accurate and useful clinical tool for AC/A determination is the comparison of heterophoria measure¬ ments with and without plus or minus lenses at a given distance. The prism diopter ( ) difference is divided by the lens power to arrive at the AC/A. This latter method is called the gradient, or lenticular, stimulus method of determining AC/A. Three techniques for determining AC/A may be summarized: 1. Response: A laboratory test that utilizes an objective refracting device

(most accurate). 2. Gradient, or lenticular, stimulus: A heterophoria comparison at a fixed distance with and without plus or minus lenses (useful clinical tool).

3. Distance-near comparison: A fre¬ quently used method of determining the AC/A (least accurate because un¬ known near factors may produce un¬ clear results).

Perception A very ment

was

interesting clinical experi¬

carried out in which sub¬

jects viewed their feet while wearing base-out prisms.17 They obviously had to "overconverge" because of the re-

quirements imposed by the prisms. When the prisms were removed and the normal amount of convergence was employed, the subjects over¬ estimated the distance of their feet. A brief conditioning period convinced them that a certain amount of con¬ vergence was needed to fuse the im¬ ages of their feet. Less convergence meant the objects were farther away. Similar types of experiments in which subjects reached for objects while viewing them first with and then without horizontal prism indicated that after a period of conditioning, experimental subjects reached for ob¬ jects in space in a direction and to an extent indicated by the amount of muscle pull they anticipated should be related to the position of the object in space. According to the authors, this indicates that registered or condi¬ as opposed to actual, conver¬ gence is a factor in perception at close range, and that appropriate adapta¬

tioned,

tion after a conditioning period occurs within the motor system for each eye. This suggests that past pointing, which occurs in recent ocular muscle palsy, particularly sixth nerve palsy, is influenced by interpretation of the amount of innervation supplied to a muscle relative to the usual local¬ ization associated with this amount of innervation. An object moving in front of the eyes in the fronto-parallel plane while the eyes are fixed on a stationary point appears to follow a path of el¬ liptical depth." However, when the eyes follow the object, the eyes ap¬ pear to follow the true path, making only conjugate movements and not em¬

ploying

convergence

or

divergence.

The combination of retinal stimula¬ tion and one other act, such as head movement or eye movement, seems necessary to allow us proper ori¬

entation. The appreciation of this Pulfrich effect is suggested as a pos¬ sible test for the presence of periph¬ eral stereopsis.19 Careful laboratory study indicated that lateral inhibition in the normal eye of a patient with anisometropia, amblyopia, and central fixation was ten minutes of arc diameter in the normal eye and 17.5 minutes of arc diameter in the amblyopic eye.20 This


eye was 20/60 and had demonstrated central scotoma. In¬ creased lateral inhibition may be related to the clinically apparent "crowding phenomenon" seen in am¬ blyopia; that is, adjacent optotypes in¬ terfering with central acuity.

amblyopic

no

Electrophysiology

Electromyographic study of a pa¬ tient with pure "V" pattern exotro¬ pia, that is, no inferior oblique overaction, demonstrated that the eyes abducted in up-gaze because of (or at least associated with) increased fir¬ ing of the lateral rectus.'-1 No increase in the electrical activity of the infe¬ rior oblique was noted. Increased cofiring of the medial and lateral rectus in the fixing eye of the asymmetri¬ cally exodeviated eyes offers proof that both lateral recti are more elec¬ trically active. In order to keep the fixing eye straight in upward gaze in spite of the excess firing of the lateral recti, the medial rectus of the track¬ ing eye should (and did) fire exces¬ sively. Electromyographic studies indicate that the

cause

of Duane retraction

syndrome (Stilling—Turk—Duane) is a paradoxical, anomalous innervation

of the lateral rectus of the affected eye, or a synergistic innervation of the extraocular muscles that are nor¬ mally innervated by different nerves and that are normally antagonists.22 Three types of Duane syndrome were identified: type 1, defective abduc¬ tion; type 2, defective adduction; and type 3, defective abduction and ad¬ duction. All types show narrowing of the fissure and retraction of the globe on adduction; "A," "V," and "X" pat¬ terns may be present also. Horizontal saccadic movements were measured with the use of electro-oculography in a patient un¬ dergoing surgery for exotropia per¬ formed with the aid of topical anes¬ thesia.23 After "usual" dissection of the intermuscular membrane, hori¬ zontal saccadic movements slowed in both abduction and adduction follow¬ ing disinsertion of the lateral rec¬ tus.

Essentially

no

movement

was

recorded when both the medial and lateral rectus muscles were dis¬ inserted and held taut. From this, it is

inferred that the vertical recti play important part in horizontal eye movements. Electro-oculography is suggested as a valuable tool for dif¬ ferentiating a slipped muscle from other causes of overcorrections or undercorrections. Only the former shows substantial decrease in sac¬ cadic velocity. An infrared reflection device was used to measure the speed of horizon¬ tal ocular movements over a range of 10° to 15° from the center line.24 Nor¬ mal subjects' eyes moved at an aver¬ age speed of between 410° to 485° per second. Reduction in saccadic veloc¬ ity, as recorded on paper, produces ob¬ jective evidence of extraocular muscle paresis. With this technique, improve¬ ment can be shown as well as abnor¬ mality confirmed. In a study from Japan, electrooculograms were recorded in an ef¬ fort to determine saccadic velocities in normal subjects and patients with strabismus. It was found that for 20° of movement, saccadic speeds were as follows25: no

Exotropic patients Temporal ocular movement, 549° per second

Nasal ocular movement, 405° per second Normal subjects Temporal ocular movement, 279° per second Nasal ocular movement, 346° per second

Esotropia patients Temporal ocular movement,

148°

per second Nasal ocular movement, 300° per second

Certainly, exotropic patients

move

their eyes with the greatest facility. The eyes move less rapidly in the field away from their chronic devia¬ tion, especially in patients with eso¬ tropia. Perhaps this is so because of chronic contractions of the muscles in the direction of the deviation. Fi¬ nally, nasal movement, which is in the direction of convergence (toward fu¬ sion of most objects), is more rapid than temporal movement in the nor¬ mal subject. Electromyography electrodes were placed at various depths in both horizontal and vertical extraocular

muscles, and recordings were made during tracking, vergence, saccadic movements, vestibular counter-roll¬ ing, levator activity, and blinking.20 Deep muscle fibers (near the globe)

showed activity later in recruitment, and muscle fibers more superficially located (away from the globe) showed earlier recruitment in muscle activity. Since this pattern was found in each of the types of eye movement, it is suggested that various histologie muscle fiber types are functionally differentiated on the basis of the amount of work they do, rather than on the basis of the type of eye move¬ ment to which they contribute. Donders law was found to be inap¬ plicable to a comparison of the tor¬ sional orientation of an eye during steady fixation and during a smooth, following movement when instanta¬ neous evaluation of the eye position was recorded.27 The eye sees an object in a way modified by how it got there relative to certain controlling or mod¬ ifying effects in the complicated nervous system. The authors state that there are some important differ¬ ences in the neural substrates for smooth tracking and saccadic modes of eye movements. It also seems reasonable to infer that there are differences between static and dy¬ namic states relative to perception. Voluntary nystagmus that is of high frequency, low amplitude, and short duration is suggested as being seen in malingerers or hysterics.28 It may also be seen as a "parlor trick" carried out by someone who has noth¬ ing to gain but the joy of entertain¬ ing those in his immediate company. In either case, this condition is char¬ acterized by the absence of abnormal

neurologic signs.

Studies showed that the viewing of vertical line suppressed horizontal pendular oscillations in one patient.29 Preferential cortical development of vertical line detection is proposed as an explanation for this phenomenon. Even in complete darkness, an eye that "intended to look" because of acoustic stimulation developed nys¬ tagmus.30 Therefore, latent nys¬ tagmus could be elicited by monocular visual attention. The asymmetric cor¬ tical influence on horizontal gaze tone a


by the intention to "look with eye" could become manifest by defective compensation from patho¬ logic brain stem centers. Eleven alert patients had ocular movements determined by electro-oc¬ ulography under conditions of bilateral patching, monocular patching, and no patching.31 Binocular patching de¬ creased frequency of eye movement by a mean of 44% and decreased am¬ plitude by 20%. Monocular patching induced one

did not decrease the

frequency or am¬ plitude to an important degree. Peri¬ odic vertical conjugate movement of the eyes occurred only during bilat¬ eral patching. It has not been deter¬

mined whether the decreased ocular movement that occurs with bilateral patching has a beneficial therapeutic effect in cases of retinal detachment, traumatic hyphema, or other condi¬ tions that may be treated with bilat¬ eral patching. "Black patch delirium," a term used to describe the agitation and delirium that may accompany bi¬ lateral patching, is well known, and it is suggested that these hazards should be weighed carefully against the uncertain gain that may be ob¬ tained from bilateral patching. EYE MOVEMENTS In case you are interested, the owl's eyes do move! Not much, though, only a maximum of 1.5°. The main tech¬ nique for the owl's looking at his en¬ vironment is still neck rotation, which may be carried out up to 270° .32 Inves¬ tigators are warned that the owl is not the epitome of the stationary eye. But, for those interested, a mixture of gallamine triethiodide and tubocurarine is effective in eliminating eye movements in the macaque monkey.31 Cyclofusional movements in hu¬ mans were confirmed to be artifacts due to subjective observational meth¬ ods.34 Compensatory eye movements are not induced by cyclodisparate stimulation. The author argues that motor compensation for tilt would provide false clues and would actually be disadvantageous to locomotion. It remains that the converse is not true; that is, tilting or torsion of the globe, such as occurs with superior oblique palsy, does cause cyclodiplopia, espe¬ cially in bilateral cases, and this can

disappear when the

eyes are moved out of the field of the paretic muscle or

muscles.

TYPES AND CAUSES OF STRABISMUS

One hundred patients had esodevia¬ tion at distance fixation and a smaller esodeviation or relative exodeviation at near fixation. No anomalies of di¬ vergence were suspected, so diver¬ gence

paralysis

was

not

diagnosed.35

The author proposes divergence pa¬ ralysis remains a rare condition and states that it seems reasonable to suppose that distance esodeviation may result from a weakness or dys¬ function of a complex vergence mech¬ anism serving both convergence and

divergence.

A group of investigators found that most children by age 2 years were easy to examine and had completed

their

emmetropization.30 In a study of

1,200 2-year-olds, 90% had a refrac¬ tion of between piano (no refractive error) and +3.00 hyperopia, 5% had

astigmatism, 4.6% had anisometropia, and 2.2% had strabismus. Forty-eight percent of patients with strabismus also had anisometropia. Early exami¬

nation is recommended. There is no to delay examination because of supposed lack of cooperation. Ab¬ normalities when found early can be treated more effectively. A northern Canadian group of 4,450 persons, more than half of whom were Eskimos, was studied to determine the prevalence of stra¬ bismus in an otherwise unselected population.37 This study, to our knowl¬ edge, is the first to produce statistics that indicate that divergent stra¬ bismus is more common than conver¬ gent strabismus, at least for the group studied. While previous studies show that esotropia or esophoria pa¬ tients outnumber those with exode¬ viations by from 20 to 1 to 2.6 to 1, this study shows the ratio of individ¬ uals with esodeviation to those with exodeviation as 0.62 to 1—more with exodeviation. One explanation is that this is an entirely random or unre¬ lated population and that, since other studies reported on clinical popu¬ lations, the latter would be expected to uncover more people with esodeviareason

tion because they would seek the aid of a clinic for cosmetic reasons. That is, an esodeviation is more likely to be constant and cosmetically unaccepta¬ ble, and an exotropia is more likely to be intermittent and cosmetically acceptable. The role of the "wide open spaces," of increased light from snow reflection, and presumably of reduced near vision requirements in the Es¬ kimo population could also be consid¬ ered to increase the likelihood of exo¬

tropia.

A case of Duane syndrome associ¬ ated with nevus of Ota is described.38 Axial anisometropia was also noted. It was pointed out that Duane syn¬ drome is frequently associated with other congenital anomalies. These in¬ clude nystagmus, epibulbar dermoids, anisocoria, blepharoptosis, kerato¬

persistent pupillary mem¬ brane, microphthalmia, heterochro¬ mia iridis, congenital cataract, colobomas, prominent epicanthal folds, persistent hyaloid artery, ectropion of the lower lid, and myelinated nerve fibers. It is also pointed out that 40% of patients affected with Duane syn¬ drome have axial myopia. In addition, an association of Duane syndrome conus,

with both Goldenhar and Wildervonk syndromes has been established. This high incidence of associated anom¬ alies has led some authors to postu¬ late a disturbance in normal em¬ bryogenesis during the second month of gestation, despite the fact that no teratogenic stimuli have been elicited to date. Cyclic deviations received their share of attention during the review period.39 A 4-year-old child developed an esotropia suddenly, and over a pe¬ riod of several months a cyclic pat¬ tern evolved. In addition to a 30 eso¬ deviation in the primary position, a "V" pattern with overaction of the in¬ ferior oblique muscles and under¬ action of the superior oblique muscles was noted. Treatment with anti¬ cholinesterase was not successful, and since the strabismic phase was in¬ creasing in time, surgery was done. A 4.0-mm bimedial recession and bila¬ teral recession of the inferior oblique muscles produced straight eyes with good fusion. The patient was observed postoperatively for a period of 22


months. Another child with cyclic esotropia was described who for two consecutive years was noted to have his cycle change on his birthday.40 A survey to determine the fre¬ quency of occurrence and character¬ istics of cyclic strabismus confirmed that cyclic esotropia is a rare entity.41 A group of ophthalmologists repre¬ senting 541 "man years" in the prac¬ tice of ophthalmology with a special interest in strabismus were polled and reported that they had treated and/or seen only 13 cases. Average characteristics of these 13 new cases, plus an additional 30 previously re¬ ported cases, are as follows: Onset, 3 to 4 years of age Deviation, 30 to 40 esotropia Vertical incomitance, mild "V"

pattern

Refraction, ± 2.25 diopter hyper¬ opia Vision, ± amblyopia AC/A, may be high Response to glasses, ± fusion

Response good

to

surgery,

usually

Usual cyclic pattern, 48 hours Other cyclic forms of strabismus were described.42 One case is de¬ scribed that was characterized by pe¬ riodic alternative nystagmus (PAN), alternating head turn, and esotropia. The whole sequence from one null point to the other took about two minutes. The cycle was: left esotropia with null point nystagmus in right gaze to right esotropia with null point nystagmus in left gaze and back again. Neurologic lesions have been found associated with three docu¬ mented cases of PAN. These were compression of the medulla, midline posterior fossa lesion, and astrocytoma of the frontal lobe. Cyclic oculomotor paralysis is ei¬ ther congenital or develops in early childhood.43 The sphincter of the pupil and some or all of the muscles inner¬ vated by the third nerve in the in¬ volved eye are affected by paralysis on a cyclic basis. The cause of this condition remains obscure. Two au¬ thors, however, speculate that there is a partial aplasia or destruction of the oculomotor nucleus sparing those ganglion cells that control the mus¬ cles involved in the cyclic movements.

Also, there is a supranuclear lesion, allowing automatic rhythmic impulses originating in a diencephalic center

on the intact cells of the ocu¬ lomotor nucleus and thereby causing the cyclic phenomena. Palsy of the superior oblique muscle is certainly not a rare entity, and sev¬ eral hundreds of cases have been re¬ ported. Knapp proposes seven classes of superior oblique muscle palsy44: Class 1.—Greatest hypertropia in "opposite" upward oblique muscle field (field of action of the homolateral antagonist, inferior oblique

to act

muscle).

Class 2.—Greatest hypertropia in "opposite" downward oblique muscle field (field of action of the paretic su¬ perior oblique muscle). Class 3.—Greatest hypertropia in entire "opposite" field (fields of action of both the paretic superior oblique and antagonist inferior oblique mus¬

cles).

Class 4.—Greatest hypertropia in entire "opposite" field and across lower field. Class 5.—Greatest hypertropia across lower field. Class 6.—Bilateral superior oblique muscle palsy. Class 7.—Traumatic paresis plus re¬ striction of relaxation of superior oblique muscle. Each class of superior oblique muscle palsy may be treated with a particular type of vertical muscle weakening or strengthening, which has as its main goal the achievement of concomitance. A rare involvement of the superior oblique muscle is superior oblique myokymia.45 It is characterized by

rapid, small-amplitude, rotary os¬ cillations of the globe limited to one eye. It causes the subjective com¬ plaints of monocular oscillopsia and torsional diplopia. The syndrome is usually benign, and the cause is ob¬

symptoms may be alle¬ viated with carbamazepine. Yet another cause of sixth nerve palsy was found, and another compli¬ cation of anesthesia described.40 Fol¬ lowing prolonged general anesthesia (7 hours, 45 minutes with halothane), a young boy developed a sixth nerve weakness. Fortunately, both the anscure, but the

esthesia and the sixth nerve palsy were transient; the patient survived with straight eyes. A new neuro-ophthalmologic entity is described.47 The most striking fea¬ ture to the ophthalmologist is bilat¬ eral ptosis that has its onset in the late preteens or early teens. This is accompanied by external ophthalmo¬ plegia of horizontal and vertical movement. Other features are abnor¬ mal skeletal muscle, retinal degenera¬ tion, normal pupils, elevated cerebro¬ spinal fluid protein, ataxia, extensor plantar response, small stature, and an abnormal ECG. In addition to the authors' one patient, 22 similar pa¬ tients are presented from the litera¬ ture. A bundle branch block was the predominant cause of death in these patients during the third decade. Cogan, as a result of study of 30 pa¬ tients with paralysis of down-gaze, proposes four categories of down¬ gaze paralysis48: (1) reverse Parinaud syndrome; (2) paralysis associated with choreo-athetosis; (3) paralysis with parkinsonism; and (4) a mis¬ cellaneous category. Only patients with evidence of central nervous sys¬ tem disease were included in the study. Command or pursuit down¬ gaze was absent, but "doll's head" downward movement was present, indicating intact vestibular re¬ sponses. Absent down-gaze causes great difficulty with the use of bifo¬ cals and unsteadiness and dizziness if the head is bent forward. Reverse Parinaud syndrome is presumed to be caused by lesions in the mesencephalon causing the findings of paralysis of down-gaze, convergence paralysis, and absent pupillary reflex. Down¬ gaze paralysis in a variety of patients with choreo-athetosis is presumably caused by a similar type of brain stem diseases as that which causes the choreo-athetosis. No specific lesion could be said to be the cause of down¬ gaze paralysis in four patients in whom histopathologic studies could be performed. In one patient whose dis¬ ease was in the miscellaneous cate¬ gory, down-gaze paralysis followed alleged surgical recession of both me¬ dial recti. Further study of this pa¬ tient, with a comment about the pres¬ ence or absence of lower lid ptosis,


would be of interest. These words of MacKenzie, uttered in 1855, are paraphrased: "The cause of squint should be sought elsewhere than in the muscles of the eye, else¬ where than in the retina, that is to say, in the brain and the nerves, or¬ gans which preside over the associa¬ tion of acts of muscles of the eyes."49 A statistical analysis of a large group of patients with congenital esotropia leads the author to conclude that two groups of patients with congenital esotropia exist, one group with neuro¬ logic dysfunction and one without. The unstable or variable group may be associated with amblyopia, ocular muscle palsies, cerebral palsy, latent nystagmus, alternating sursumduction, hyperkinetic status, "A" and "V" patterns, high AC/A, anoxia, an¬ esthesia intoxication and drugs, plus absense of fusion. Strabismus with¬ out neurologic dysfunction is more stable and is more amenable to surgi¬ cal treatment. It is pointed out that 5% of normal children have stra¬ bismus, but 50% of children with brain damage have strabismus. Microtropia or microstrabismus is redescribed by Lang as a manifest strabismus of less than 5° (9.4 ).5" Three forms are described—primary

constant, primary decompensating,

and secondary microstrabismus. A re¬ markable incidence of 42% of all con¬ vergent strabismus in the author's personal practice fit the criteria of

microtropia. Convergent microtropia

40 times more frequently encoun¬ tered than divergent microtropia. It is stressed that amblyopia is the most important problem in microstrabis¬ mus. A treatment program utilizing filters of decreasing density is de¬ scribed. Ultrasmail angle strabismus con¬ tinues to receive attention in sharp contrast to its size. Variations in atti¬ tudes toward small-angle strabismus led to perhaps one of the more apt names for microtropia or monofixa¬ tion—"The Thing," a term coined by Marshall M. Parks, MD. A suggestion was made by Gunter . von Noorden, MD, that inconspicuously small an¬ gles of strabismus with a variety of sensorial adaptations and a variety of causes comprise a small part of the was

spectrum of strabismus and that the

lumping together of strabismus of less than 5° adds nothing to eliminate confusion. Finally, anomalous retinal correspondence (ARC) as a cause of microtropia is denied. In spite of the

fact that all differences have not been resolved, Dr. J. Lang of Zurich, Switz¬ erland, should be commended for the zeal with which he has pursued the study of ultrasmall angle strabismus. The term "monofixation syndrome" continues to gain popularity in de¬ scribing patients with straight or nearly straight eyes, peripheral fu¬ sion with fusional vergence ampli¬ tudes, gross stereopsis, and a facul¬ tative scotoma including the macula of the nonfixing eye.51 Amblyopia is a common finding, but eccentric fix¬ ation is said by the author to be rare although some investigators have found minimal eccentric fixation a constant finding in pure anisometro¬ pia amblyopia with strabismus (ie, microstrabismus). It is important to recognize this entity ("the thing") as a frequent and satisfactory end result of strabismus treatment. It has also been stressed by von Noorden that pure anisometropic amblyopia with¬ out other findings has been the cause of unnecessary neurologic or neurosurgical evaluation by the non-oph¬ thalmologist. Our medical colleagues should be warned of the possibility of performing expensive and sometimes

dangerous,

unnecessary tests

on

per¬

with microstrabismus. If one searches diligently, ultrasmall angle strabismus can be found almost anywhere. Monofixation syn¬ drome was diagnosed in 15 flying per¬ sonnel, twelve of whom were conver¬ gent and three divergent.52 These patients represented the spectrum of microtropia. Their conditions ranged from microtropia with identity, as de¬ scribed by Lang, to small-angle mani¬ fest strabismus with good peripheral fusion. This study demonstrates that even among a group of individuals se¬ lected, at least in part, because of good vision, careful studies of visual function can uncover departure from complete normality. The changes from "normal" to clinical strabismus seem to exist as a continuum or a spectrum. In another study of the visons

suai function of air flight personnel, it is suggested that normal oculomo¬ tor balance gradually deteriorates, particularly when correction for

changing anisometropia is not worn.53 Fitness tests at regular intervals are suggested for flight crew members so that proper decisions regarding optic or orthoptic training may be made, thus prolonging the career of a given

member. Exodeviations were found in nearly one quarter of cases of strabismus ex¬ amined over an eight-year period in white South Africans.54 This figure compares to a high incidence of exo¬ tropia in other countries that also have a high light intensity. It is well known that in any intermittent exo¬ tropic patient, bright light tends to cause the exodeviation to be more likely to be manifest. An interest¬ ing cause-and-effect relationship is hinted at. crew

SENSORY ADAPTATIONS

Amblyopia Factors that have been held respon¬ sible for amblyopia production were reviewed by von Noorden.55 Strabis¬ mic amblyopia originates from confu¬ sion, which actually is not different from retinal rivalry. The fovea of the nonpreferred eye presents a "confus¬ ing" image that is overruled by an "out of balance" retinal rivalry situ¬ ation. This, rather than diplopia, is more likely to be the amblyopiogenic factor. In anisometropic amblyopia, dissimilarity of foveal images is also the cause of the amblyopia. It is em¬ phasized that since the accommoda¬ tive requirement of the fixing eye is imposed on the deviating eye and that since this may not be appropri¬ ate to focus the object seen by the de¬ viating eye, this deviating eye suffers from anisokonia or blurring of this image. Form deprivation amblyopia, which has been called amblyopia "exanopsia," may occur bilaterally or unilaterally, with the latter being more severe. There are some sim¬ ilarities between the three types of amblyopia. First, none of the three types occurs after the age of suscepti¬ bility, which in humans appears to be until age 44/2 or 5 years. Second, a certain degree of visual deprivation


in all three

types. Therefore, image incongruity and stimulus dep¬ rivation seem operative in all three types of amblyopia in that they cause neurophysiologic anomalies in the occurs

striate and prestriate cortex and mor¬ phologic changes in the lateral gen¬ iculate body that are similar. These changes have been confirmed in the primate (rhesus monkey) and are as¬ sumed to

in humans. found to occur on a "meridional" basis in uncorrected astigmatism.50 After optical correc¬ tion of the astigmatic error, large dif¬ ferences in acuity for gratings ori¬ ented in the vertical and horizontal meridian were found. This defect was established as being neural rather than optical in nature. "Sustained," sensitive cells were found in the cat's area centralis, and less sensitive "transient" cells were found in the cat's peripheral retina.57 The more sensitive central sustained cells require a sharply-focused image to respond, while peripheral transient cells are less affected by defocusing. Sustained cells also require a tempo¬ rally stable image. A third type of occur

Amblyopia was

cells, suppressed by contrast,

appears to terminate exclusively in the supe¬ rior colliculus. A three-neuron set-up is proposed: sustained cells for sharp

vision, transient cells for attentiongetting, and suppressed-by-contrast

cells for slow tracking. The authors conclude that amblyopia in all pre¬ disposing conditions is caused by the fact that the sustained foveal cells are deprived of visual stimulation, rather than by active suppression. Light deprivation in the form of patching for amblyopia was found to produce depression in the electro¬ retinogram (ERG) affecting both the "a" and the "b" wave in visually ma¬ ture (older than 6 years old) sub¬ jects.58 These changes occurred in both amblyopic and normal eyes. The amblyopic eye had been patched when inverse occlusion was carried out. These ERG changes occurred after as little as one month of patching, and all ERGs reverted to normal after a period of one to several months when patching was discontinued. This study points out that if occlusion with an opaque contact lens is carried out

to preserve the retina in certain

cases

of tapetoretinal degeneration, it would be difficult to follow these pa¬ tients with ERG findings. The visually evoked response (VER) produced by a pattern-reversal stimu¬ lus with similar and dissimilar timing to the two eyes demonstrated a dif¬ ferent response in a functionally am¬ blyopic eye and a normal eye.59 What was considered an abnormal response to VER in the amblyopic eye could be improved with occlusion; however, a lack of binocularity, at least as far as VER response was concerned, became apparent as vision improved after patching of the better eye. Although acuity of 20/60 or less is required to give an abnormal VER, in one case an eye with an acuity of 20/30 had a se¬ vere depression in VER after three months of patching. When patching was stopped, the VER of the better eye reverted to normal. The amblyo¬ pic eye with the patch off lost several lines of vision: however, the VER pat¬ tern did show "binocular" character¬ istics. It is proposed that the VER may be a useful tool as an objective assessment of binocularity, as well as a technique for differentiating hys¬ terical from true amblyopia. A simple flash stimulus does not lead to record¬ ing of VER changes. A checkerboard or stripe pattern presented as a phase-reversal stimulus through pola¬ roid or similar techniques is required. This work promises to offer at least the more sophisticated facility yet an¬

other useful, objective test that may be applied to obtain information from patients with whom only objective tests can be used. Nineteen patients who underwent occlusion of one eye for reasons other than treatment of amblyopia early in life (16 within 13 months of age and three within 36 months of age) had

amblyopia."" Electroretinogram test¬ ing was normal, and VER testing was abnormal. Stimulus deprivation am¬ blyopia was the name given to this type of visual loss. It should be

stressed that short periods of occlu¬ sion lasting only a week can produce amblyopia in a young child with a

susceptible nervous system. While most ophthalmologists are aware of the possibility of occlusion strabismus

in young children, others, such as surgeons who may deal with lid anomalies in childhood, should be made aware of this very real danger.

plastic

The fundi of 1,000 infants were ex¬ amined in the first 24 hours of life with the use of the indirect ophthal¬ moscope."1 Retinal hemorrhages were found in 245 infants (24.5%). The macula was involved in 18 (1.8%). Five patients with hemorrhages, none of whom were younger than 4 years of age, had follow-up examinations for determination of visual acuity, motor alignment, sensory status, and ap¬ pearance of the fundi. All find¬ ings were normal. The authors were unable to confirm neonatal macular hemorrhage as a cause of non-oph-

thalmoscopically detectable, organic amblyopia (relative amblyopia). They point out, however, that other condi¬ tions, such as hemorrhages into the optic nerve or transitory inflamma¬ tory disease,

may be

a cause

of

or¬

ganic amblyopia. Amblyopia treatment remains a challenge, and patching of the better eye along with stimulation of the am¬ blyopic eye seems to remain the

treatment of choice. Several sheets

with geometric designs and laby¬ rinths of decreasing size were de¬ scribed for home correction of am¬ blyopia.02 The amblyopic child colors various designs and traces the course of the labyrinth. A newspaper that contains print of varying size has also been used by some ophthalmologists as a home cor¬ rection exercise for amblyopia. Chil¬ dren are asked to circle all the "Es" or "Os" on the front page. The pre¬ printed sheets are more expensive but may be more effective. Proof of this, however, has not been shown. One author suggests for amblyopia treatment the use of self-adhesive pa¬ per applied to a spectacle lens.03 This reduces visual acuity to 20/4,000 and is a useful, cosmetically acceptable technique for "on glass" occlusion. It is stressed that patients with ac¬ quired esotropia should have their eyes straightened and amblyopia eliminated as soon as possible after the onset of the deviation to obtain central fusion.04 The amblyopia is treated with a patch, but the point is


suppression is treated only by eliminating the need for suppres¬ made that

sion. This means that the eyes must be straight with both eyes open. The authors accomplished this with glasses, miotics, prisms, surgery, and reoperation. Using this routine in 50 patients with acquired esotropia, 24% obtained central fusion, 52% obtained peripheral fusion, and 24% demon¬ strated no fusion. Patients with endresult small-angle esotropia that is cosmetically acceptable should not have their suppression eliminated be¬ cause they depend on this mechanism for visual comfort. Visual

Acuity and

Fixation

Four types of response were found when patients with strabismus or amblyopia were tested with the Bagolini glass by Bagolini himself"5: (1) harmonious ARC; (2) complete sup¬

pression; (3) incomplete suppression; and (4) diplopia. The last is a rela¬ tively rare response. As a diagnostic tool, these glasses, which seem to be "micro-Maddox rods," add little new

information to what can be inferred by the astute clinician. Bagolini glasses have been used, largely in Eu¬ rope, as part of a treatment program that does not interrupt casual seeing but that allows awareness of the use of one or both eyes simultaneously. Various ocular movements were tested in Little League players and, along with age, some ocular functions were found to correlate significantly with batting average.00 These were up-down and side-side pursuits. Little League officials apparently also found a positive correlation between Tai¬ wan pitching and low batting aver¬ ages and banished the former. So much for the Little Leaguers. NONSURGICAL TREATMENT Prisms Prisms

slightly

are used to just correct or to overcorrect patients with

strabismus so that they may be in¬ duced to use their foveas together.07 The overcorrecting prisms are worn until retinal correspondence is said to be normal in space, and then the proper amount of prism is prescribed to place the object of regard on the foveas without convergence. While

this type of treatment has been popu¬ lar in Europe, it remains for any North American author to report really worthwhile results employing prism therapy for any type of stra¬ bismus other than that which is of an acquired nature and which has nor¬ mal sensorial relationships. The ad¬ vent of press-on prisms made in the Fresnel principle have not yet pro¬ duced the therapeutic breakthrough, at least in this country, that was pre¬ dicted by some.

Orthoptics of 79

Analysis patients with stra¬ bismic amblyopia and eccentric fix¬ ation who were treated extensively with pleoptics, administered by three experienced orthoptists trained in the Bangerter and Cuppers techniques,

carried out."8 The authors arrived following conclusions: Given a patient with strabismic amblyopia and eccentric fixation, a poor result with pleoptic therapy could be expected with: was

at the

Fixation, >30° Angle, >15

nasal

< 2 years of age Occlusion of good eye, < 4 years of age

Onset, A be

more

favorable

expected with:

prognosis could

Fixation, < 30° nasal Angle, < 15 Onset, >2 years of age Occlusion, none of any type

Twenty-five percent of 86 patients with amblyopia, eccentric fixation, and poor results with conventional

amblyopia treatment (good-eye patch¬ ing) received what the authors con¬ sidered lasting good results with pleoptic therapy carried out for one

half hour once a week for from four to 35 weeks.09 After fixation became central, patching was switched from the amblyopic eye to the dominant eye. Criterion for success was consid¬ ered to be 20/40 visual acuity that was maintained. Less than two lines of improvement on the vision chart was considered a failure. With a fol¬ low-up period of successfully treated patients of one to four years, 65% of the successfully treated patients re¬ tained good results. None of the pa¬ tients who were originally helped slipped back to less than 20/80 visual

acuity. Patients ranged in age from 4 to 41 years of age. Another paper described

a

con¬

trolled study that compared results obtained from extensive pleoptic treatment and results obtained from conventional occlusion. It bodes ill for the proponents of pleoptics. The sum¬ mary of a paper is quoted to avoid

misunderstanding:

Two groups of children comparable in age, refractive error, fixation pattern, and uni¬ formity of therapy were studied. It was found that, in regard to normalization of fixation, visual gain, and duration of treat¬ ment, treatment of amblyopia with pleop¬ tics had no advantage over treatment with occlusion of the dominant eye. Occlusion is preferred to pleoptics in the treatment of amblyopia with eccentric fixation. It is con¬ cluded that pleoptics should be reserved for particularly selected patients for whom occlusion of the dominant eye is not pos¬ sible.70

On a more positive note, conven¬ tional occlusion (of the good eye) re¬ sulted in 95% effectiveness in normal¬ izing fixation in cases of eccentric fixation in the amblyopic eye.71 In¬ verse occlusion in cases of amblyopia with eccentric fixation appeared only to prolong the length of treatment and to be of no inherent therapeutic value. A stereoscopic viewing device (Viewmaster) is suggested as an aid in training for binocular vision. In or¬ der to insure binocularity, a horizon¬ tal thread is placed over the area of view of one eye and a vertical thread in the area of view of the other eye.72 The subject must see a "cross" over the picture to insure use of both eyes. The apparatus is inexpensive, readily available, and the range of picture material is enormous. EXAMINATION TECHNIQUES

A small black and white television is suggested as an effective fixation device to be used in the ex¬ amining room for adults as well as children. It is more durable, less expensive, and more versatile than motorized toys and other fixation de¬ vices currently available.73 As a means of controlling fixation in various fields of gaze by using a system of coordinates, a pinhole 2.0 mm in diameter in a small moveable screen


of cardboard that may be at¬ tached to a glass frame has been de¬ scribed.74 Repeat measurements are said to be more accurate, because in severely incomitant strabismus, the amount of deviation may change one prism diopter for each degree of change in gaze angle. Such tech¬ niques suggest the question, "What is the relationship of measurements of deviation angle, amounts of surgery done, and results from surgery?" It was pointed out that accuracy and consistency of measurement can have

piece

medicolegal implications. A prism telescope (one half of a 7 x 50 binocular instrument) with a light source attached may be used to produce and interpret a corneal light

reflex at a distance of six meters.75 This ingenious device allows the light reflex test to be performed and inter¬ preted during distance fixation. Angle kappa is described as the angle formed by the primary line of sight and by a line perpendicular from the center of the pupil (pupillary axis).70 This angle is measured with the troposcope; a positive angle is ec¬ centric toward the nose and a nega¬ tive angle is eccentric toward the temporal side. Patients with eso¬ tropia were more likely to have posi¬ tive angles kappa and hypermetropia. There was also a relationship be¬ tween higher hypermetropia and larger angles kappa. Individuals with straight eyes had about an equal chance of having either a positive, a negative, or no measurable angle

kappa. Exotropic patients were more likely to have a negative angle kappa. Myopic exotropia patients were most likely to have a negative angle kappa. The angle kappa must be taken into

consideration when strabismus is measured by interpreting the corneal light reflex, especially in cases of dragged macula such as those that oc¬ cur in retrolental fibroplasia. Saccadic velocities measured with electro-oculography proved useful prognostically in patients with blow¬ out fractures or suspected blow-out fractures of the floor or medial wall of the orbit.77 Electro-oculographically measured saccadic movements also correlated well with muscle force val¬ ues determined with the active force

generation test. When the difference between upward and downward sac¬ cadic velocity was less than 30%, pa¬

able to fuse either with¬ or after surgical repair. This speed of movement indicated no real muscle weakness. In contrast, pa¬ tients with a difference in vertical saccadic velocities of 51% or more had persistent vertical diplopia. The lat¬ ter probably indicates inferior rectus muscle weakness. A Goldmann perimeter may be em¬ ployed to plot subjectively the field of single binocular vision.78 This is espe¬ cially useful to provide accurate, re¬ producible evidence of a patient's ocu¬ lar motility status after a palsy of one or more muscles, such as worsening or improvement of a deviation. The field of binocular vision in a normal sub¬ ject resembles a "base up," essen¬ tients

were

out surgery

tially equilateral triangle measuring

110° from base to apex. A normal in¬ dividual will see the light singly in the entire inverted triangle with both eyes. Of course, outside the triangle the light is seen singly with only one eye because of the obstruction of the nose or brow. Some or nearly all of the area within the triangle will be an area of double vision with paresis of one or more extra ocular muscles. This test is simple to perform, quick, accurate, and reproducible. A tongue blade placed between the eyes and the printed page while a pa¬ tient is reading can help determine subtle differences in visual acuity be¬ tween the two eyes under binocular conditions.79 This technique should also be useful for studying the sco¬ toma in small angle strabismus in a patient who is a good observer. Torsion can be measured best with the use of the double Maddox rod test.80 Torsion nearly always occurs in bilateral palsy of the superior oblique muscle, and frequently occurs in uni¬ lateral palsy of this muscle. There is no quantitative relationship between ocular torsion and vertical deviation, horizontal deviation, incomitancy, or head tilt findings. A computerized "stepping prism" was used to show that it takes one minute for a test individual's lateral phoria to reach its maximum measur¬ able value and that this value re-

mains essentially constant during up to three minutes of continued test¬ ing.81 The "stepping prism" method was suggested as a valid way of mea¬ suring lateral phorias. The eyes must first have fusion broken with a basein or base-out prism, and the patient must then be allowed ample time to refuse. The maximum prism displace¬ ment that is refusable after up to one minute of prism dissociation is a mea¬ sure of the lateral phoria. Prism displacement exceeding the lateral phoria will lead to a diplopia response. The pattern of response to a comput¬ erized "stepping prism" test was variable on an individual subject basis. Quantified forced duction testing was carried out using two differential transformers, one for force and one for displacement. Fifty grams of force applied to the globe along a tan¬ gent from the point of fixation moved the eye 12.1 mm ± 2.0 mm in normal subjects.82 In abnormal subjects with conjunctival scars, double elevator pa¬ ralysis, and overaction of the inferior

oblique muscles, displacement was a case of myasthenia gravis, injection of edrophonium chloride had a measurable effect. It is suggested that this technique can be useful to less. In

show the state of muscle tone. As done clinically, force ductions are car¬ ried out after the eye has moved vol¬ untarily as far as it can go in the di¬ rection of movement to be tested. The amount of force needed to complete the movement, if indeed it can be completed, is the usual force or pas¬ sive duction test. The random-dot stereogram objects described by Julisz are seen in depth without monocular recognition of the contours of objects.83 Random-dot stereograms seem to have great po¬ tential use in both looking for the presence of and for determining the quality of stereopsis. Investigations of stereo-acuity in small-angle stra¬ bismus should be revealing. Of inter¬ est, relative stereo-blindness is more pronounced in right hemisphere le¬ sions than left hemisphere lesions. A random-dot, steroscopically pre¬ sented "tumbling E" was found to be a reliable screening device for the de¬ tection of amblyopia.84 Passing the


random dot E (RDE) in the normal range (1 meter card-to-subject dis¬ tance or better—equivalent to 250 arc-

seconds or better) is indication that the person screened is normal or near normal. On the other hand, passing the RDE at 40 cm or less or failing the test indicates a high probability of amblyopia. This test is easy for the tester to administer and simple for the child tested to understand. It also takes into consideration both visual acuity and binocular cooperation, and, according to the authors, deserves further study. The incidence of amblyopia has been reported for the general popu¬ lation at between 1% and 3%.85 How¬ ever, since such screening should be done at an early age (3 to 4 years of age) some children may be untestable. When only cooperative, testable children are screened using current techniques, such as Snellen letters,

prevalence figures are higher (2% to 12%). Stereoacuity measured with the Titmus technique was employed as a screening device for amblyopia in 70 patients. The following conclusions were made: Passing the stereoacuity test by seeing the fly and up to four circles cannot discriminate reliably patients with amblyopia from normal subjects. One patient with 20/300 vi¬ sual acuity in the more severely af¬ fected eye passed this test. Passing

the test with the No. 5 circle (100 arcsecond disparity) was reliable. None of 16 patients passing this test had more than one line difference be¬ tween the two eyes, acuity in the more severely affected eye of less than 20/30, or notable strabismus. The importance of monocular clues produced by offset and giving spurious, good stereoacuity results was stressed. As acuity decreases, stereoacuity also decreases on a linear basis, ac¬ cording to one author.80 At lower lev¬ els of acuity, monocular clues are thought to be utilized. Vision testing in preschool years can be accomplished at 2% years of age using matching Snellen letters.87 Other tests requiring directionality or form recognition can be used in chil¬ dren starting at age 3. Some tests that may be used in preschool testing

are

Allen

picture cards, illiterate

test, illiterate "E" test for home

"E" test¬

the National Society for Prevention of Blindness), Sjogren hand test, Home Test for Parents (American Academy of Pediatrics), Michigan preschool test, and Snellen letters as matching objects. Home eye tests, while offering the opportunity to reach more children more easily, carry with them the distinct possi¬ bility of under-referral. The weak link in such a system, of course, is that an inexperienced person both administers and interprets the test. Even when the most accurate testing is done, failing children must be treated if they are to benefit. Three diopter-plus lenses have long been used as an accessory while per¬ forming the prism-and-cover test at close ranges in a patient with exo¬ tropia.88 The stated purpose of this test is to determine the effect of accommodative convergence on the near deviation. Since even a normal person will have an increased exode¬ viation or decreased esodeviation at near when tested with a +3.00D lens, it is suggested that the AC/A should be determined in such patients at the distance (lenticular method) with the introduction of a -2.00D or -3.00D lens. Prolonged occlusion to disrupt fusional convergence is suggested as the best technique to uncover the true, fusion-free, near deviation.

ing (from

SURGICAL TREATMENT General Principles A new synthetic absorbable suture material, polyglactin 910 (Vicryl), was found to produce a satisfactory suture

Braided

for

strabismus

surgery.89

polyglactin suture was and more pliable than ani¬ stronger mal products (collagen or catgut) both in size 6-0 and 5-0. Polyglactin 910 produced no apparent allergic reac¬ tion or chronic granulomas. The su¬ ture strength remained a sufficient length of time to insure adequate muscle-globe union. Studies carried out in rabbits and humans confirmed

lasting properties and minimum reac¬ tion. Another polyglycolic acid suture (Dexon) was used in the 4-0 size for

muscle union and in the 6-0 size for conjunctival closure, and it was com-

with chromic catgut sutures of the same size from the same manu¬ facturer for recession and resection operations in 26 patients.90 The syn¬ thetic absorbable suture was stronger and produced less tissue reaction at the three-week postoperative inter¬ val. Postoperative reaction was sim¬ ilar to gut at the one- and 12-week postoperative intervals. The synthetic absorbable suture handled as well as silk, but it did become "adherent" to Tenon capsule during tissue passage. A retinal detachment surgeon sug¬ gests the use of four Dacron sutures to attach the rectus muscles to the sclera 12.0 mm posterior to their in¬ sertion in cases of gross nystagmus with retinal tears.91 The horizontal muscles alone may be attached in hor¬ izontal nystagmus, the vertical mus¬ cles alone attached in vertical nys¬ tagmus, or all four muscles may be sutured to the globe if both a vertical and horizontal component exists. Converse and Smith, and later and more extensively Paul Tessier, sug¬ gested major bone revision surgery for such conditions as Apert syn¬ drome, Crouzon syndrome, and Treacher-Collins-Franschetti syndrome, as well as hypertelorism and vertical displacement of the orbit.92 The pro¬ liferation of such procedures will nec¬ essarily require involvement of those opthalmologists interested in stra¬ bismus problems. Both preoperative and postoperative evaluation of such patients should be carried out, since strabismus may be present preopera¬ tively or even produced by the sur¬

pared

gery. A study of 103 consecutive patients with pure blow-out fracture led to the conclusions that (1) the optimum time for repair when indicated is within 10 to 14 days, and (2) about 50% of pure

blow-out fracture

patients require

surgery.93 The indications for surgery

diplopia not resolving in a few days; a large fracture with herniation are

into the antrum; tissue incarceration with globe retraction; and enophthal¬ mos of greater than 3.0 mm. When late repair of a blow-out fracture is done in those who meet the criteria for early repair, a high complication of both diplopia and enophthalmos is found. Even successful early repair


had

a

higher initial incidence of di¬

plopia than one would like, in that 31% required further surgery of the muscle or orbit, or both. "Masterly inactivity" (judicious restraint) is touted as the procedure of choice for those not requiring surgery. A study of 345 strabismic children suggested that in late onset stra¬ bismus, refractive errors were signif¬

icant and vertical deviations in¬ These late onset strabismus patients had a better chance of regaining binocular func¬ tion than did those patients with early onset. Early onset strabismus also had a higher incidence of vertical deviation. Refractive errors were less important in the early onset group with the exception of anisometropia. Delayed surgery in early onset cases was said to reduce the likelihood of obtaining a functional result. Thirty-four percent of 123 patients with Down syndrome had strabis¬

frequent.94

Twenty-eight percent (34 pa¬ were esotropie, and 6% (eight patients) were exotropic. Both accom¬ mus.95

tients)

modative

and

nonaccommodative

esotropie patients responded to either glasses or surgery in a manner sim¬

ilar to what one would expect in an otherwise normal patient. Patients with exotropia had similarly good re¬ sults. The author suggests that pa¬ tients with Down syndrome should have their strabismus diagnosed early and treated vigorously as with an otherwise normal patient. A modified Kestenbaum operation for horizontal face turn in congenital nystagmus is accomplished by start¬ ing with a recession of the lateral rec¬ tus muscle opposite the head turn and proceeding with yoke recessions and resections.90 The lateral rectus muscle on the side opposite the head turn is recessed 6.0 mm; its yoke, the con¬ tralateral medial rectus muscle, is recessed 5.0 mm. The medial rectus muscle of the eye directed opposite the head turn is resected 7.0 mm and its yoke muscle, the lateral rectus muscle in the contralateral eye, is re¬ sected 8.0 mm. Nine of ten patients treated with this procedure had defi¬ nite improvement in head position. In addition, three patients with nullpoint nystagmus causing chin eleva-

tion or depression were treated with recession of the vertical rectus muscle opposite the head shift and resection of the vertical rectus muscle in the di¬ rection of the head shift. For ex¬ ample, if the chin is elevated and the eyes look down to nullify the nys¬ tagmus, the inferior recti would be recessed and the superior recti re¬ sected. For head elevation or depres¬ sion of 20° or less, only the recession was done. When head elevation or de¬ pression was greater than 20°, the re¬ section was also done. The recession or resection was always 4.0 mm. One patient had all four horizontal rectus muscles recessed and resected in the usual manner and both superior recti recessed 4.0 mm for chin depression, vertical as well as horizontal, null-

point nystagmus.

As with any surgery requiring hospitalization, strabismus surgery is accompanied by anxiety both on the part of the patient and the parents.97 Several factors are important with regard to lessening this anxiety level. These include a sympathetic physi¬ cian, "live in" hospital facilities for the patient's family, open discussion with parents and older children, in¬ telligent use of sedation and anal¬ gesia, avoidance of unnecessary bilateral bandages, especially of and use su¬ absorbable patches, tures. Answers to commonly asked questions include: "Yes, strabismus surgery is serious; any operation re¬ quiring general anesthesia is seri¬ ous." "No! The eyeball is not taken out during strabismus surgery." A decrease of 10% or more in the heart rate was considered an expres¬ sion of the oculocardiac reflex in 243 patients in whom surgery on 623 ex¬ traocular muscles was done.98 An overall positive oculocardiac reflex rate of 67.9% for patients and 48.6% for muscles occurred. The reflex oc¬ curred more frequently in female pa¬ tients when the lateral rectus and inferior oblique were tested and it oc¬ curred more frequently in the right eye of male patients. Horizontal Strabismus

A study of the results obtained from surgery for infantile esotropia was carried out using data from 143

One hundred five patients had esotropia diagnosed by an ophthal¬ mologist before 12 months of age. These patients were said to have in¬ fantile (congenital) esotropia. Thirtyeight patients with esotropia that definitely developed after one year of age were said to have acquired eso¬ tropia. Several previously noted facts were confirmed, including the follow¬ ing: (1) the rate of satisfactory surgi¬ cal correction was higher in acquired than in congenital esotropia; (2) more patients had fusion; and (3) fewer patients had amblyopia postop¬ eratively in the acquired than in the congenital esotropia group. In the congenital esotropia group, 54% of pa¬ tients received a satisfactory surgical cases.99

correction after the first surgery and 84% after the second surgery. Pa¬ tients who were within 10 of having straight eyes were considered as being treated successfully. Those pa¬ tients with congenital esotropia suc¬ cessfully treated with surgery before the age of 2 years had better results, that is, more fusion and less am¬ blyopia, than those treated after two years of age. Fusion was defined as a deviation of 10 or less along with demonstration of fusion with the ma¬ jor amblyoscope, stereo test, or the Worth four dot test. This type of pa¬ tient seems to fall within the classifi¬ cation of small-angle esotropia with peripheral fusion or monofixation. Al¬ though 20 patients were treated sur¬ gically quite early, between age 6 and 12 months, these patients are not identified in the statistical analysis. Evaluation of the surgical results, in¬ cluding sensory testing, was done at the "diagnostic age," that is between 4 and 5 years of age. Twenty-one patients with near eso¬ deviation 10 or more greater than their distance deviation underwent bimedial rectus recession of between 3.0 and 5.0 mm.100 The patients were carefully selected, and none had amblyopia, anisometropia, cerebral palsy, or hypermetropia greater than + 3.75; these are all factors that lead to an increased incidence of sec¬ ondary exotropia. Of those patients on whom surgery was performed, the greater the deviation, the more effect obtained per millimeter of surgery;


and conversely, the smaller the devia¬ tion, the less effect per millimeter of

surgery. Most undercorrections were obtained in small deviations that re¬ ceived small amounts of surgery (bimedial 3.0 mm recession). In no case was the smaller distance deviation overcorrected by the surgery aimed primarily at correcting the greater near deviation. Similar results were obtained in intermittent and con¬ stant esotropie patients with regard to motor alignment. As would be ex¬

pected, patients with intermittent esotropia were more likely to be converted to a phoria than were con¬ stantly esotropie patients. The au¬ thors suggest that "clinical appli¬

cation of such correlations should allow increased accuracy of stra¬ bismus surgical results." Nonsurgical treatment and measurement of the AC/A by more accurate techniques than distance/near comparison were not discussed. An extensive statistical analysis of 456 esotropie patients treated surgi¬ cally at one hospital by or under the supervision of the staff surgeons was carried out.101 No important differ¬ ence in cosmetic success or prognosis was found regarding race, sex, family history, hyperopia, onset of squint, age at which surgery was performed, conditions such as or associated mongolism. Partially accommodative cases did better than nonaccommodative ones. Patients with cerebral palsy had poorer results. Very few pa¬ tients were operated on before age 2 years, so not much can be said about results from early surgery. Ambly¬ opic patients did just as well as nonamblyopic patients, and the age of onset of strabismus was not an important factor in the outcome of surgery. These are surprising conclu¬ sions. Most patients were undercorrected. Excellent results were con¬ sidered 0 to 9 esotropia. A study of 530 children with stra¬ bismus was carried out to determine a relationship between age of onset of strabismus and timing of surgery.102 Those patients who had visual acuity of 20/40 or better in their deviated eye and who had the onset of their strabismus before 2 years of age had best results when surgery was per-

formed within two years of the onset of strabismus. If the onset of stra¬ bismus occurred after two years of age, the timing of surgery was not important. Early surgery was thought to be more beneficial in the first category than any gain that could have been expected from exten¬ sive preoperative orthoptics, which would have delayed surgery. Forty-eight patients with exotro¬ pia were treated with a single 7.0 mm lateral rectus muscle recession and 55 patients with esotropia were treated with a single 4.0 mm medial rectus muscle recession.103 Eighty percent of the exotropic patients with between 15 and 30 of deviation preopera¬ tively and with good fusion potential without a hyperdeviation received what was considered a good result. Sixty-five of those patients with eso¬ tropia undergoing a 4.0 mm medial rectus muscle recession received a good effect. Those esotropie patients with deviation of 20 or less and nor¬ mal retinal correspondence (NRC) were more likely to receive a good re¬ sult. In both esotropie and exotropic patients who obtained good results, an average of 19 of deviation was corrected at distance testing. Pa¬ tients with poor responses had on the average only between 6 and 9 change postoperatively at the dis¬ tance. The authors' intent seemed to be that of reporting results rather than convincing the reader that a large, one-muscle operation should be done rather than a smaller, twomuscle operation. The records of the 103 patients represent pooled data from a group of staff surgeons and senior residents. No mention is made of any postoperative incomitance, a finding that is not uncommon after a single rectus muscle recession. It is pointed out that large amounts of exotropia can be corrected in adults with amblyopia utilizing only recession of the lateral rectus muscle and resection of the medial rectus muscle of the amblyopic eye.104 In a series of 22 patients, correction varied from 30 to 105 , and all patients were helped substantially from the cosmetic standpoint with just one op¬ eration. In each case, the lateral rec¬ tus muscle recession was between 7.0

and 8.0 mm. The variable aspect of the operation was the medial rec¬ tus muscle resection, which was up to 14.0 mm. The large medial rectus muscle resection acts as a "stay su¬ ture," and postoperatively, patients will experience some limitation in abduction because of this in the oper¬ ated eye. Such patients should be un¬ dercorrected as compared with pa¬ tients in whom functional results are expected. In patients for whom a functional cure is intended, an early postoperative overcorrection is desir¬ able. This cosmetic, large-angle exo¬ tropia correction is a "mechanical" one and is enhanced by relaxation of tight conjunctiva laterally by either a conjunctival recession or a "T" clo¬ mm

sure.

Vertical Strabismus and "A" and "V" Patterns

One author

that superior actually bilat¬ apparent only after

warns

oblique paresis that eral may become

is

treatment of the more in¬ volved side.105 After surgery, the sup¬ posedly uninvolved side will then manifest a superior oblique muscle palsy. Bilaterality should always be suspected in cases of traumatic sixth nerve palsy. The presence of a "V" pattern and cyclodiplopia with evi¬ dence of excycloptropia of one or both eyes as determined with the double Maddox rod test should alert the ex¬ aminer to the possibility of bilateral but unequal superior oblique muscle

surgical

palsy. Temporal transposition of the supe¬

rior rectus muscle and nasal trans¬ position of the inferior rectus muscle is a technique suggested for treat¬ ment of extorsion caused by superior oblique muscle underaction in a case in which the superior oblique muscle could not be found.100 The patient showed improvement both in head po¬ sition and ocular alignment after this

procedure.

Three theories explaining Brown superior oblique tendon sheath syn¬

thickened sheath of the abnormal innervation; and isolated inferior oblique paresis.107 The author states that probably the best explanation is that of a stenosing tenosynovitis as drome

are:

superior oblique tendon;


the cause of the observed phenomena of this syndrome. This is so because the condition may be intermittent, can be cured by mechanical change, and has been cured by steroids. Brown syndrome occurred in one "wear and tear" case in which the trochlea angle was more acute be¬ cause the tendon inserted entirely medial to the superior rectus muscle. The reviewer has also seen two pa¬ tients in whom the superior oblique tendon inserted entirely medial to the superior rectus muscle. In these cases the only extraocular muscle problem was excyclotropia of the involved eye. The true nature of the Brown supe¬ rior oblique tendon sheath syndrome remains unanswered. A technique is described for local¬ izing and cutting the superior oblique tendon at the insertion after it has been removed from its sheath.108 This produced a reduction in the exodevia¬ tion of 30 on the average in down¬ gaze when performed bilaterally for "A" pattern exotropia with bilateral overaction of the superior oblique muscles. These findings are similar to those obtained when the superior oblique tenotomy or tenectomy is car¬ ried out nasal to the superior rectus muscle, and they challenge the con¬ tention that more superior oblique muscle weakening is obtained when the tenectomy is carried out nearer to the trochlea. A history of inferior oblique muscle weakening procedures was reviewed by Parks.109 Those techniques dis¬ cussed included measured recession, disinsertion, myectomy near the in¬ sertion, and myectomy near the ori¬ gin. The author states a clear pref¬ erence for recession of the inferior oblique muscle with reattachment at a predetermined place on the sclera. In a prospective study, the most fre¬ quent complication of the inferior oblique muscle weakening was per¬ sistent overaction. This occurred in 79% of patients undergoing disinsertion, 37% of patients undergoing myectomy at the insertion, and only 15% of patients who had recession of the inferior oblique muscle. Myec¬ tomy near the origin, according to the author, should not be done. The "ad¬ herence syndrome" is described as a

relentless hypotropia with mechanical restriction to elevation, occurring in 13% of patients who had myectomy of the inferior oblique muscle at the insertion done by the author. The author has never produced this syn¬ drome with a measured recession. He reports a total of 26 cases of "ad¬ herence syndrome" including those seen for other ophthalmologists. This condition was treated by an average of 2.6 vertical muscle operations with an average improvement of 11 in patients who had an average preoper¬ ative hypotropia of 19 . No instances of bifed insertion of the inferior oblique muscle were encountered in 1,600 inferior oblique muscles whose insertions were identified. This tends to reinforce the notion held by some that there are more "anomalous sur¬ geons" than anomalous muscles. One hundred-six patients under¬ went resection of one lateral rectus muscle and had weakening, by my¬ otomy or disinsertion, of the inferior oblique muscle on the same side.110 Thirty-seven (35%) had anywhere from slight to severe hypotropia in that eye. Fourteen of these patients were treated surgically, and thirteen had good results, but the release of scar tissue was difficult. Patients who developed this hypotropia did so within two years, but since there is a delay, it is doubted that hemorrhage alone could be the cause. Suture reac¬ tion may also be a cause. This condi¬ tion is somewhat different than the "adherence syndrome" described pre¬

viously.

What in effect is a "Z" or marginal myotomy of the inferior oblique muscle near its insertion is de¬ scribed.111 This may be done with an electric knife or with scissors after crushing the muscle. Of the authors' 86 patients undergoing this procedure unilaterally or bilaterally, all had had surgery on from two to four vertical muscles previously. This makes re¬ markable the statement that 45 of the 86 patients had an "exact" correc¬ tion (± 1°). The correction of up to 6° of vertical deviation after undergoing "Z" myotomy of the inferior oblique muscles is at variance with most re¬ ports. In a review of this article, the statement is made that a "Z" my-

otomy is hard

to

accept

as a

logical

and effective means of weakening the inferior oblique muscle.112 In a retrospective study, 106 pa¬ tients underwent unilateral weaken¬ ing of the inferior oblique muscle by a variety of techniques.113 A substantial number of these patients developed overaction of the previously normal or

"slightly" overacting, unoperated,

inferior oblique muscle. A normally acting inferior oblique muscle devel¬ oped overaction after weakening of its overacting counterpart in one third of the cases, and if even the slightest overaction was noted preop¬ eratively, two thirds of unoperated inferior oblique muscles became overactive. This occurred in three fourths of cases by six months postopera¬ tively. In 23 patients with unilateral overaction of the inferior oblique muscles and who were not operated on, three fourths became bilateral within six months. The pattern is similar whether or not horizontal sur¬ gery is done and in patients with esotropia, exotropia, or no tropia in the primary position. The age of the patients is not specified, and no men¬ tion is made of specific tests for supe¬ rior oblique muscle palsy, such as the Bielschowsky test or the double Maddox rod test for cyclotropia. Inferior oblique muscle weakening done bilaterally and as the only surgi¬ cal procedure produced no important change in the primary position align¬ ment in 84% of 50 patients.'14 Of those patients who had some change in pri¬ mary position alignment, none had more than 8 . Six percent manifested an eso-shift of more than 3 and cur¬

iously (after weakening

an

abductor),

10% had an exo-shift of more than 3 . From this paper it can be inferred that weakening the inferior oblique muscles in a patient with straight eyes in the primary does not cause a meaningful change in the primary position alignment. This paper does not establish criteria for doing sur¬ gery for oblique muscle overaction in a patient with straight eyes in the

primary position.

Paralytic Strabismus Sixteen cases of sixth nerve palsy treated with vertical muscle

were


union as described by Jensen.115 Pa¬ tients had both congenital and ac¬ quired sixth nerve palsy. In each case the medial rectus muscle was re¬ cessed. Two of five patients described in detail had only minimal restriction to forced abduction. The average pre¬ operative deviation was 40 , and postoperatively it was 2 . The aver¬ age postoperative abduction from the midline was 18°. Preoperatively no patient could move the eye laterally beyond the midline. No cases of ante¬ rior segment ischemia were seen in spite of the fact that all four rectus muscles were operated on. Apparently two remaining anterior ciliary ar¬ teries in the nasal portion of the ver¬ tical recti remain functioning and are sufficient to nourish the anterior seg¬ ment. It has yet to be determined how much blood passed through that portion of the muscles that are united. The authors recommend re¬ cession of the medial rectus in cases where greater than 25 of esotropia is present in the primary position. An author suggests the term "dis¬ placement without disinsertion" to be used instead of "rectus muscle union" for the procedure first suggested by Hildreth and later applied clinically by Jensen for rectus muscle paraly¬ sis.110 The author reports satisfactory results in four of six patients under¬ going displacement of the vertical rectus lateral halves to the upper or lower halves of the lateral rectus muscle. The author's findings are es¬ sentially in agreement with those re¬ ported previously by Jensen, and by Henderson and Helveston. It is pointed out again that move¬ ment of the insertion, or belly, of a muscle on the globe while at least part of the muscle remains attached to the globe should be called trans¬ position.117 This was originally pointed out by Verhoeff. In a detailed, extensive laboratory and clinical study, one author establishes the feasibility of true extraocular muscle autotransplantation. Autogenous ho¬ mografts of muscle lose their muscu¬ lar properties but do act as effective muscle-tendon lengthening devices. One patient who underwent reopera¬ tion after muscle transplantation had very little adherence between the

transplanted extraocular muscle and underlying sclera. It is suggested that heterotransplantation may be feasible. The inferior oblique may be "sacrificed" for transplantation, and obviously, the resected portion of ei¬

ther the medial or lateral rectus could be used as a tendon lengthening transplant to the recessed antagonist. A good result from transposition of the superior oblique tendon in one case of congenital third nerve palsy is described.118 Primary position mea¬ surement changed from 70 exo¬ tropia to straight, and 15° of adduc¬ tion was present after surgery as compared to adduction only to the midline preoperatively. A satisfactory treatment of the cyclotropia associated with superior oblique muscle palsy, according to one author, consists of splitting the supe¬ rior oblique muscle insertion and both advancing and anteriorly displacing the anterior portion of the superior oblique tendon.119 This was done bilat¬ erally along with bilateral inferior oblique recession to treat bilateral su¬ perior oblique muscle palsy. The au¬ thor reports one patient treated suc¬ cessfully by this technique. It was emphasized that traumatic fourth nerve palsy should be tested carefully for fusion and cyclodeviation. A "T" shaped, Hess-Lee screen wand and torch enables torsion to be evaluated. The sensory status of 11 coopera¬ tive patients with Duane retraction syndrome was evaluated with the questions in mind: Do these patients experience diplopia, and if so, how do they cope with it?120 Only two pa¬ tients complained of double vision spontaneously, but in all patients double vision could be elicited. All pa¬ tients who were tested for stereopsis demonstrated it, indicating bifoveal fixation. Also, on appropriate testing and when their attention was called to it, all patients were able to recog¬ nize diplopia. It was impossible to plot a suppression scotoma as can be done in most cases of horizontal stra¬ bismus with sensory adaptations. In¬ stead of suppression in the usual sense, patients with Duane syndrome assume a characteristic head posture to enable fusion, or they seem to sim¬ ply ignore the doubled image at other

times and thus remain unaware of it. Recession of the medial rectus muscle and temporal transposition of the vertical recti was carried out in 67 patients with Duane syndrome.121 Eleven had straight eyes preopera¬ tively, and 56 had some degree of eso¬ deviation. All patients had less esode¬ viation in the primary position after surgery, and 12 had exodeviation. An average of 21° of abduction was pro¬ duced postoperatively. No patient was noted to have anterior segment ischemie signs. The author credits careful surgical techniques for this result. Indications for surgical treat¬ ment of Duane syndrome are stra¬ bismus that is manifest in the pri¬ mary position and/or a cosmetically unacceptable head turn. The surgery, when successful, gives the patient ab¬ duction at the expense of decreased adduction. Other surgeons prefer single medial rectus muscle recession of the affected eye in mild cases, bimedial recession in more severe cases, and a three recession procedure that adds recession of the lateral rectus muscle of the affected eye. The latter procedure is especially aimed at re¬ ducing lid fissure narrowing during adduction on the involved side. Duane syndrome was found bilater¬ ally in four patients spanning three generations of a family.122 A woman, her son, and two grandchildren were similarly affected, except that the children (aged five and one years) were able to adduct their eyes, while the father in the fourth decade of life had moderate limitation of adduction and the grandmother in the sixth dec¬ ade had severe limitation of adduc¬ tion. This pattern of occurrence sug¬ gests a hereditary, genetic pattern of autosomal dominance. It is suggested by the authors that Duane syndrome is a progressive syndrome complex because with the passage of time, sec¬ ondary fibrosis in the medial rectus muscle leads to a decrease in adduc¬ tion. Since all four of the patients in this family had essentially straight eyes in the primary position, no treat¬ ment other than the prescribing of glasses was carried out. Another au¬ thor reported a 7-year-old girl had Duane syndrome and congenital ptosis on the same side.123

LEARNING DISORDERS study of 751 Japanese elemen¬ tary students, no correlation could be found between refraction anomaly and/or strabismus, amblyopia, and reading ability.124 While children with minor neuropsychological defects may also have strabismus, the strabismus per se is not considered the cause of the reading difficulty. Instead of con¬ sidering care of the eyes in isolation when reading difficulty is encoun¬ In

a

tered, an interdisciplinary approach is suggested. Presumably because of their idiographic written language, reading difficulty is said to be rela¬ tively infrequent in Japan. It was in¬ teresting to note that in spite of what was considered normal intelligence, 5.3% of the students were one year or more behind in reading ability. Of 78 dyslexic children, 21 showed

accommodative

insufficiency.125 Three

of the 21 showed accommodative fa¬

tigue. Treatment by orthoptics

was

carried out in 15 with restoration of normal accommodation and conver¬ gence ability. An improvement in

point symptoms was not accom¬ panied by relief from dyslexia. This was yet another negative study deal¬ ing with the role of the eyes and vi¬ sion in dyslexia. Two groups of boys (15 each) with near

difficulties in academic achievement were studied.12" One group had visuomotor impairment as determined by the Bender-Gestalt test, and the other group had no visuo-motor im¬ pairment. The results were that chil¬ dren who draw poorly are character¬ ized by disorders of perceptual analysis and have visuo-motor im¬ pairment. Both of these defects could

be expected to retard reading ability, but there is no ready explanation for why those without visuo-motor im¬ pairment had academic difficulties. It is not only ophthalmologists who have problems clinically correlating identifiable signs with learning dis¬ ability. So-called "soft neurological signs" diagnosed by the pediatrician or neurologist, although suspected of

being related

to

learning disabilities,

also hard to pin down.127128 Two simple tests may be done by the oph¬ thalmologists, however, that may in¬ dicate the need for further neurologare


ical examination. These simple tests are asking the patient to read a para¬ graph, and also asking him to draw a man

such

plus

as a

a geometric type picture bicycle or a clock. Immature

drawing, poor use of space, failure

to

the midline in what should be a symmetrical figure, and poor reading of a paragraph that is appropriate for the age may suggest the presence of a minor neurologic deficit. cross

Electro-oculogram testing was em¬ ployed to determine that refixation is more

accurate from the dominant

side in patients with clearly estab¬ lished right or left eye and hand dominance.129 Patients with mixed dominance, such as right-handed pa¬ tients with left eye preferred or lefthanded patients with right eye pre¬ ferred, showed no consistent pattern. It has been shown previously that mixed dominance and right or left eye-hand dominance has no relation¬ ship to reading ability, a task that re¬ quires left-to-right fixation. The problem of eyes and dyslexia has been in a confused state for many

years, partly because it seems that for every well thought out paper, there are two nonsensical counter¬ parts. In an example of the latter kind of paper, it was determined that binocularity is a very important fac¬ tor in reading, because children read less well when a lens that produces a retinal distortion is worn before one eye.130 Come to think of it, Jesse Owens ran slower with a tack in his

shoe,

too.

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scopic


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