29
Thyroid-associated eye disease: clinical management Symptoms and signs Patients with thyroid-associated eye disease may present with a wide variety of symptoms that are not always recognised immediately as features of this disorder. These symptoms range from puffy swollen eyelids, which sometimes develop overnight, to an abnormal head posture with chin elevation of such an extent that, for example, driving is difficult. Gritty and irritable eyes are common, but in some patients intolerance to contact lenses that were previously comfortable may be the only complaint. There may be watering of the eyes at any time and not solely in response to cold wind or irritants such as smoke. Some patients have profuse flooding of the eyes with tears; this can happen at night and wake them. Double vision, typically with vertically separated images, appears on waking but resolves after a few minutes, only to recur later if the patient becomes very tired, or indulges in a single alcoholic drink or a short post-prandial sleep. (This pattern of ocular movement is typical and provided the initial impetus to my interest in this fascinating but often frustrating condition.) That one eye is seemingly more widely open than its fellow may be due to lid retraction, protrusion of the globe, or both. Thyroid-associated eye disease is the obvious diagnosis when these signs are bilateral, but it is also the commonest cause of unilateral proptosis. Conjunctival injection (especially over the four rectus muscles) with chemosis may develop as the proptosis increases. The later stages of an inflamed protruding eye in which the lids cannot close over the swollen red conjunctiva with a dry cornea lead to corneal ulceration, infection, and endophthalmitis. By contrast, other patients may notice gradually decreasing visual acuity in one eye, often preceded by reduced brightness of colours in that eye, with only slight fullness of the lids and little proptosis. These two widely different features of the disease process have surprisingly similar therapeutic requirements. Other signs support the clinical suspicion. For example, there may be lid lag on downgaze--usually an asymmetrical decrease in the normal downward movement of the lids. A localised excess of conjunctiva at the medial canthus may overlap the lower lid punctum and thus prevent normal tear drainage, as does the reduced blink frequency (fig 1). Syringing through the nasolacrimal passages shows that the tear drainage channels are usually patent. Thickening of the conjunctiva at the upper limbus, which may encroach into the cornea, will stain with Bengal rose; this confirms the superior limbic keratitis,! which disappointingly fails to correlate positively with severity of gritty irritation. The lower third of the cornea can appear dry and also take up stain where there is incomplete eye closure during sleep. Diplopia is not due to superior ophthalmoplegia, as was believed for many years, but to tight fibrosed ocular muscles that do not extend fully when their antagonist contracts. Fibrosis of the inferior rectus, the most frequently affected muscle,2 causes diplopia on attempted upgaze; the images are more widely separated if the patient tries to look up when the affected eye is in the abducted position. Reduced abduction is due to a tight medial rectus, and the less common decrease in infraduction follows fibrosis of the superior rectus. Additional evidence of restricted elevation is provided by measurement of the intraocular pressure (IOP) in the primary position and then on attempted upgaze, when the IOP may increase by 6 mm Hg or more. In view of
the age range of these patients (25-78 years), surprisingly few have chronic simple glaucoma as well. In thyroid-associated eye disease, the proptosis is usually straight forwards; displacement of the globe in any other direction is suggestive of other diagnoses. For example, proptosis in the downwards and medial direction points to lacrimal gland enlargement, and that with a downwards and outwards displacement could be due to a frontal sinus mucocele or a dermoid cyst. Fundal examination may reveal obvious optic disc oedema, but the early signs of optic nerve compression need to be searched for carefully. These signs include fullness of the retinal veins, which no longer pulsate on the slightest
Fig 1-Patient with bilateral proptosis and bilateral lid retraction.
Centre. The conjunctiva is injected and oedematous particularly lower lid margin at medial end. Oedema fluid has collected more beneath the left eye than the right eye. Top Attempted upgaze shows reduced elevation on both sides but more so on the right than the left as indicated by corneal reflex within the pupillary area. Bottom. Downgaze shows that the left eye is divergent and both eyes show some decrease in total downward rotation This position reveals lid lag which is more pronounced on the left side than on the right.
along
ADDRESS: Moorfields Eye Hospital, City Road, London EC1V 2PD (Mr P. Fells, FCOphth).
30
translid pressure on the globe; the finding that in severe the veins remain distended and the retinal arterioles collapse in a pulsatile manner before being temporarily obliterated points to raised intraorbital pressure. Chorioretinal striae are no longer regarded as characteristic of an intraorbital tumour but they can occur in thyroidassociated eye disease. If the folds, typically horizontal, pass through the macula they can cause loss of acuity, which may become permanent if the raised orbital pressure is not relieved within weeks. cases
History The patient may have a history of hyperthyroidism or, less often, of goitre, sometimes many years earlier. There may be a family history of these conditions. Early evidence of current thyrotoxicosis should be sought—eg, weight loss despite increased appetite, changes in temperature preference, shakiness of hands, weakness of proximal limb girdle muscles, and mood changes (especially of increasing irritability). A few patients may have primary hypothyroidism either previously or at presentation, but hypothyroidism secondary to over-treated thyrotoxicosis is much more
common.
Investigations The diagnosis of thyroid-associated eye disease is a clinical one that may be supported by tests. Thyroid function tests of free thyroxine, triiodothyronine, and thyroid stimulating hormone (TSH) should be measured. Autoantibodies that should be sought include antithryoglobulin, antimicrosomal, and antigastric parietal cell antibodies. In some instances thyroid stimulating antibodies (also known as TSH receptor antibodies) may be measured. Raised antibody levels support the diagnosis but are not conclusive. In the adjoining article, Professor Weetman reviews current knowledge about autoimmunity in this disorder. Enlarged extraocular muscles can be demonstrated by ultrasonography, preferably B-scan, and by computed tomography (CT).3 CT scans in the horizontal axis can occasionally mislead and views in the coronal plane, either direct or computer enhanced, give unequivocal crosssections of all the ocular muscles. Magnetic resonance imaging (MRI) has been claimed to give even better views of the orbital apex (fig 2) when evidence of optic nerve compression by the enlarged muscles is being sought. The absence of irradiation risks and hence the possibility of serial examinations may make MRI the method of choice if costs can be controlled. Incipient optic nerve compression is evidenced by falling visual acuity, reduced visual fields (but no generally agreed typical changes), relative afferent pupillary reaction defect, and altered colour vision with decreased colour contrast sensitivity along the tritan (blue) axis.4
Treatment
Surgical decompression When vision is threatened seriously by optic nerve compressionor the proptosis is so severe that corneal exposure is progressing to ulceration and endophthalmitis, surgical decompression is the method of choice.6,7 In addition to surgery for visual loss or jeopardised integrity of the globe, there is an increasing tendency for some surgeons to offer decompression for cosmetic reasons alone. As a minimum, the medial half of the orbital floor and the medial wall need to be breached to allow orbital fat under pressure
to escape into the antral and ethmoidal sinuses, respectively. There are different routes to achieve this end:
The last route gives best optic nerve decompression right up to the orbital apex. The orbital periosteum is opened with posterior-to-anterior longitudinal incisions over its distal half and with circumferential incisions anteriorly to allow the pressurised orbital fat to herniate out into the sinuses. This increased space for orbital contents gives an average 4-5 mm reduction in the exophthalmometer measurements. When even greater decompression is needed some surgeons include a third orbital wall-the lateral. Naffziger’s transfrontal route through the roof of the orbit is rarely used nowadays because of much higher morbidity than with the other routes. Solely cosmetic decompression may be done with the Tessier bicoronal scalp incision after the front third of the scalp has been shaved.8 As this wide skin flap is reflected forwards and downwards, the whole of the orbit may be exposed with access to all four walls if necessary. By whichever route, it is usual to decompress both sides at one operation since both are often affected but to different extents. Any of these methods may cause sensory changes in infraorbital nerve territory and some increased epiphora but both effects are normally temporary. All patients may have a worsening of their ocular movements, which become more esotropic, and often with an A-pattem-ie, worse on upgaze-which persists in some patients.
Symptomatic treatment Many patients have much
less yet substantial ocular involvement for which such drastic intervention is not needed. Artificial tear drops can be used to relieve irritable eyes—eg,
hypromellose (Hypromellose Eye-drops, BPC)
which can be used as often as required-in addition to a lubricant at night-eg, yellow soft paraffin (Simple Eye Ointment BP). If lid closure is incomplete, the lids can be taped on retiring. Broad tape (2-5 cm wide) is best applied from the side of the nose horizontally across the closed lids for most effective closure. Oedema fluid that collects in the lids overnight can be reduced by means of an extra pillow or if the head of the bed is raised on bricks. Other patients respond well to cyclopenthiazide (’Navidrex’ [Ciba, UK]), one or two 0’5 5 mg tablets, taken at bedtime. Double vision Patients with diplopia need careful orthoptic monitoring and help.2,9 The field of binocular single vision is recorded, as is the Hess chart, which shows the movements of each eye relative to its fellow eye. If the restriction of ocular movements is symmetrical and equal, the Hess chart can give the misleading impression that the eye movements are not too severe a problem. Additionally, the range of movements of each eye is recorded separately since this is a sensitive index of how eye movement is affected. To help the patient cope with double vision, he may be shown a compensatory head posture (if he has not already discovered this for himself). Other patients benefit from wearing Fresnel, plastic press-on prisms on their glasses. These
31
Fig 2-(Top) MRI horizontal scan through orbits and (bottom) coronal indicated by arrow on MRI scan.
section taken at level
MRI scan shows
proptosis with straightening of optic nerves and enlargement of the medialand lateral optic nerves in cross-section (long arrow), enlarged medial (short arrow) and inferior (middle length arrow) rectus muscles, together with the enlarged lateral and superior rectus muscles, are compressing the optic nerves at the orbital apex rectus muscles. Coronal section shows
can be changed easily at subsequent visits if the ocular restrictions are still changing. Only a few patients need temporary occlusion to block diplopia. The ocular movements are checked at 3-monthly intervals until the measurements confirm that they have been stable for 6 months, and then prisms (if not too strong) may be built into the spectacle lenses, or ocular muscle surgery may be done. Most commonly, a tight inferior rectus needs to be recessed; sometimes, the inferior recti and medial recti of both eyes may need surgery at one operation to restore at least a central area of binocular single vision. Under general anaesthesia the tight muscles are recessed; at least one of them is on a sliding suture, which can be adjusted to the optimum position the next morning under local anaesthesia (topical drops) with the help of the alert patient’s responses.1O Most surgeons undercorrect the restriction because the antagonist muscles have become very strong while working against tight muscles, and further changes in ocular muscle balance have to be allowed for as far as possible. Such an operation will mean that in some cases prisms are no longer needed or that the necessary prism is much weaker and easily incorporated into glasses.
prisms
Botulinum toxin When the patient’s ocular movement restriction is of only 12-18 months’ duration, earlier temporary relief may be given by an injection of botulinum A toxinllinto the affected muscle under local anaesthesia as an outpatient. It is thought
that the botulinum toxin cannot be working on established fibrosis but that it must be exerting its action by other means. Simonsz and Konunerell 12 have proposed recently that in the early stages, active muscle contraction and not fibrosis limits ocular rotations.12 The botulinum toxin "uncouples" this contraction by blocking neuromuscular transmission at the end plate. Even more surprisingly, in one out of six patients the effect of the toxin lasts much longer than the expected 2 months, but it is not possible to predict in which patients."
Medical decompression Patients
with moderate to pronounced ocular involvement, such as bilateral unequal proptosis and some diplopia, or evidence of incipient optic nerve compression be treated may medically. High-dose systemic
corticosteroids—eg, prednisolone 80-100 mg daily-have been used with some success to "medically decompress" the orbits.14 There is a high tendency to relapse as the steroid doses
are
reduced and often maintenance levels of 30 mg
a
day or more are needed. The medical consequences of prolonged steroid therapy are as unacceptable to some patients and physicians as is the disease. Cyclosporin alone has given equivocal results but is establishing a role when used in conjunction with a moderate dose of prednisone. 15 Intravenous methylprednisolone, Ig in 48 h, is effective" but should be used only with strict medical monitoring for inpatients. Plasmapheresis has also been used effectively but
32
the
subsequent
rebound effect
the use of workers have
necessitating
systemic steroids has meant that abandoned this procedure.
most
Radiotherapy During the past few years, radiotherapy has re-emerged as a most useful form of treatment; megavoltage, highly collimated
beams from a linear accelerator are lymphocytotoxic. The Stanford group have continued with this treatment since their 1973 paper17 and reported further results last year.18 The X-ray beam is aimed via a lateral port to give maximum dose to the retro-ocular tissues but at negligible risk to the lens and retina. These investigators found that a total 2000 cGy dose in 10 or 12 fractions over a 2-week period as an outpatient was most effective but male patients still on treatment for hyperthyroidism responded least well. A decrease in orbital tension, relieving optic nerve compression, and some decrease in proptosis and in conjunctival injection may be expected over the following 2 weeks to 3 months. Previous concern that orbital fibrosis would be increased by radiotherapy, making subsequent surgery to the ocular muscles more difficult, has proved to be unfounded. Like medical decompression by high-dose steroids, radiotherapy is most effective within the first year of onset of severe ocular changes. However, Mourits et a119 have recently suggested that it would be beneficial to identify periods of active orbital inflammation within the long natural history2O of the condition on the basis of painful ocular movements, tenderness, and increased conjunctival injection. They propose that immunosuppression by steroids or radiotherapy would be the most successful regimen during such times and should not be limited to within the first year of onset.
Lid surgery As soon as optic nerve compression has been controlled and diplopia relieved, any malposition of eyelids due to retraction of the upper or lower lid can be corrected.21 The lids are adjusted to the underlying globe and hence all ocular muscle surgery must have been completed. Persistent upper-lid retration for more than a year after any hyperthyroidism has been treated responds to disinsertion of the smooth muscle (Muller’s) component of the levator for up to 2 mm of exposed sclera. If greater than 2 mm, the levator aponeurosis should be incised at its borders also, or even recessed. Lower-lid retraction may follow inferior rectus recessions of more than 4 mm and this degree often has to be exceeded to correct severe hypotropia of the eye. Correction of the lower-lid covering is usually best done by incorporation of "spacers" of stored sclera between the lower border of the tarsal plate and the lower lid retractors. Lateral tarsorrhaphy is never done as an isolated procedure to contain increasing proptosis with chemosis because it is bound to fail. However, the procedure may be done as a final correction to give the best appearance at the same time that an upper lid retraction is being reduced for a mild inactive
proptosis. Conclusion As soon as any associated thyrotoxicosis has been controlled and care taken to avoid temporary episodes of hypothyroidism, any optic nerve compression must be treated by surgical decompression, radiotherapy, or systemic steroids. Persistent ocular movement limitations are corrected by ocular muscle surgery with prismatic
spectacle aid if necessary. Finally, the lids are adjusted to the globe for best appearance.22 Some surgeons feel confident enough to offer surgical decompression for cosmetic reasons alone for this very distressing condition. Whichever treatments are used it is rarely possible to restore either the ocular movements or the patient’s appearance to their original state. No preventive therapy is yet available, nor will it be until the pathogenesis is clarified. Meanwhile the physician has to use his limited means to deal with the various stages of orbital involvement and maintain the patient’s morale over several years with compassion and
understanding. Figures reproduced with permission of department of medical illustration (fig 1), and Dr Ivan Moseley, department of radiology (fig 2), Moorfields Eye Hospital. REFERENCES P, Doniach D, Lawton NF. Diagnosis and management of dysthyroid exophthalmos. In Proceedings of the 2nd International Symposium on Orbital Disorders Amsterdam 1973. Modem problems in ophthalmology, Basel: Karger, 14, 409-413, 1975. Fells P, McCarry B. Diplopia in thyroid eye disease. Trans Ophthalmol Soc UK 1986; 105: 413-23. Trokel SL, Jakobiec FA. Correlation of CT scanning and pathologic features of ophthalmic Graves’ disease. Ophthalmology 1981; 88:
1. Fells
2.
3.
553-64. 4. Potts M, Falcao-Reis
F, Fells P, Buceti S, Arden GB. Colour contrast sensitivity, pattern ERG’s and cortical evoked potentials in dysthyroid optic neuropathy. Invest Ophthalmol Vis Sci 31: abstract 932m ARVO,
1990. 5. Trobe JD, Glaser JS, Laflamme P. Dysthyroid optic neuropathy. Arch Ophthalmol 1978; 96: 1199-209. 6. Anderson RL, Lindberg JV. Transorbital approach to decompression in Graves’ disease. Arch Ophthalmol 1981; 99: 120-24. 7. Fells P. Orbital decompression for severe dysthyroid eye disease. Br J Ophthalmol 1987; 71: 107-11. 8. Mourits MPh, Koornneef L, Wiersinga WM, Prummel MF, Berghout A, van der Gaag R. Orbital decompression for Graves’ ophthalmopathy by inferomedial, by inferomedial plus lateral, and by coronal approach. Ophthalmology 1990; 97: 636-41. 9. Scott WE, Thalacker JA. Diagnosis and treatment of thyroid myopathy. Ophthalmology 1981; 88: 493-98. 10. Fells P. The treatment of non-comitant strabismus. In: van Balen AThM, Houtman W, eds. Docum Ophthal Proceedings Series 32. The Hague, Junk, 197-207, 1982. 11. Elston JS, Lee JP, Powell CM, Hogg C, Clark P. Treatment of strabismus in adults with botulinum toxin A. Br J Ophthalmol 1985; 69: 718-24. 12. Simonsz HJ, Kommerell G. In Graves’ disease, increased muscle tension and reduced elasticity of affected muscles is primarily caused by active muscle contraction. Neuro-ophthalmol 1989; 9: 243-46. 13. Lyons CJ, Vickers SF, Lee JP. Botulinum toxin therapy in dysthyroid strabismus. Eye 1990; 4: 538-40. 14. Day RM, Carroll FD. Corticosteroids in the treatment of optic nerve involvement associated with thyroid dysfunction. Arch Ophthalmol 1968; 79: 279-82. 15. Prummel MF, Mourits MPh, Berghout A, et al. Prednisone and cyclosporine in the treatment of severe Graves’ ophthalmopathy. N Engl J Med 1989; 321: 1353-59. 16. Kendall-Taylor P, Crombie AL, Stephenson AM, Hardwick M, Hall K. Intravenous methylprednisolone in the treatment of Graves’ ophthalmopathy. Br Med J 1988; 297: 1574-78. 17. Donaldson SS, Bagshaw MA, Kriss JP. Supervoltage orbital radiotherapy for Graves’ ophthalmopathy. J Clin Endocrinol Metab
1973; 37: 276-85. 18. Petersen IA, Kriss JP, McDougall IR, Donaldson SS. Prognostic factors in the radiotherapy of Graves’ ophthalmopathy. Int J Radiation Oncol Biol Phys 1990; 19: 259-64. 19. Mourits MPh, Koornneef L, Wiersinga WM, Prummel MF, Berghout A, van der Gaag R. Clinical criteria for the assessment of disease activity in Graves’ ophthalmopathy: a novel approach. Br J Ophthalmol 1989; 73: 639-44. 20. Hales IB, Rundle FF. Ocular changes in Graves’ disease. Q J Med 1960; 29: 113-26. 21. Waller RR. Eyelid malpositions in Graves’ ophthalmopathy. Trans Am Ophthalmol Soc 1982; 80: 855-930. 22. Shorr N, Seiff SR. The four stages of surgical rehabilitation of the patient with dysthyroid ophthalmopathy. Ophthalmology 1986; 93: 476-83.
Thyroid-associated eye disease: clinical management Symptoms and signs Patients with thyroid-associated eye disease may present with a wide variety of symptoms that are not always recognised immediately as features of this disorder. These symptoms range from puffy swollen eyelids, which sometimes develop overnight, to an abnormal head posture with chin elevation of such an extent that, for example, driving is difficult. Gritty and irritable eyes are common, but in some patients intolerance to contact lenses that were previously comfortable may be the only complaint. There may be watering of the eyes at any time and not solely in response to cold wind or irritants such as smoke. Some patients have profuse flooding of the eyes with tears; this can happen at night and wake them. Double vision, typically with vertically separated images, appears on waking but resolves after a few minutes, only to recur later if the patient becomes very tired, or indulges in a single alcoholic drink or a short post-prandial sleep. (This pattern of ocular movement is typical and provided the initial impetus to my interest in this fascinating but often frustrating condition.) That one eye is seemingly more widely open than its fellow may be due to lid retraction, protrusion of the globe, or both. Thyroid-associated eye disease is the obvious diagnosis when these signs are bilateral, but it is also the commonest cause of unilateral proptosis. Conjunctival injection (especially over the four rectus muscles) with chemosis may develop as the proptosis increases. The later stages of an inflamed protruding eye in which the lids cannot close over the swollen red conjunctiva with a dry cornea lead to corneal ulceration, infection, and endophthalmitis. By contrast, other patients may notice gradually decreasing visual acuity in one eye, often preceded by reduced brightness of colours in that eye, with only slight fullness of the lids and little proptosis. These two widely different features of the disease process have surprisingly similar therapeutic requirements. Other signs support the clinical suspicion. For example, there may be lid lag on downgaze--usually an asymmetrical decrease in the normal downward movement of the lids. A localised excess of conjunctiva at the medial canthus may overlap the lower lid punctum and thus prevent normal tear drainage, as does the reduced blink frequency (fig 1). Syringing through the nasolacrimal passages shows that the tear drainage channels are usually patent. Thickening of the conjunctiva at the upper limbus, which may encroach into the cornea, will stain with Bengal rose; this confirms the superior limbic keratitis,! which disappointingly fails to correlate positively with severity of gritty irritation. The lower third of the cornea can appear dry and also take up stain where there is incomplete eye closure during sleep. Diplopia is not due to superior ophthalmoplegia, as was believed for many years, but to tight fibrosed ocular muscles that do not extend fully when their antagonist contracts. Fibrosis of the inferior rectus, the most frequently affected muscle,2 causes diplopia on attempted upgaze; the images are more widely separated if the patient tries to look up when the affected eye is in the abducted position. Reduced abduction is due to a tight medial rectus, and the less common decrease in infraduction follows fibrosis of the superior rectus. Additional evidence of restricted elevation is provided by measurement of the intraocular pressure (IOP) in the primary position and then on attempted upgaze, when the IOP may increase by 6 mm Hg or more. In view of
the age range of these patients (25-78 years), surprisingly few have chronic simple glaucoma as well. In thyroid-associated eye disease, the proptosis is usually straight forwards; displacement of the globe in any other direction is suggestive of other diagnoses. For example, proptosis in the downwards and medial direction points to lacrimal gland enlargement, and that with a downwards and outwards displacement could be due to a frontal sinus mucocele or a dermoid cyst. Fundal examination may reveal obvious optic disc oedema, but the early signs of optic nerve compression need to be searched for carefully. These signs include fullness of the retinal veins, which no longer pulsate on the slightest
Fig 1-Patient with bilateral proptosis and bilateral lid retraction.
Centre. The conjunctiva is injected and oedematous particularly lower lid margin at medial end. Oedema fluid has collected more beneath the left eye than the right eye. Top Attempted upgaze shows reduced elevation on both sides but more so on the right than the left as indicated by corneal reflex within the pupillary area. Bottom. Downgaze shows that the left eye is divergent and both eyes show some decrease in total downward rotation This position reveals lid lag which is more pronounced on the left side than on the right.
along
ADDRESS: Moorfields Eye Hospital, City Road, London EC1V 2PD (Mr P. Fells, FCOphth).
30
translid pressure on the globe; the finding that in severe the veins remain distended and the retinal arterioles collapse in a pulsatile manner before being temporarily obliterated points to raised intraorbital pressure. Chorioretinal striae are no longer regarded as characteristic of an intraorbital tumour but they can occur in thyroidassociated eye disease. If the folds, typically horizontal, pass through the macula they can cause loss of acuity, which may become permanent if the raised orbital pressure is not relieved within weeks. cases
History The patient may have a history of hyperthyroidism or, less often, of goitre, sometimes many years earlier. There may be a family history of these conditions. Early evidence of current thyrotoxicosis should be sought—eg, weight loss despite increased appetite, changes in temperature preference, shakiness of hands, weakness of proximal limb girdle muscles, and mood changes (especially of increasing irritability). A few patients may have primary hypothyroidism either previously or at presentation, but hypothyroidism secondary to over-treated thyrotoxicosis is much more
common.
Investigations The diagnosis of thyroid-associated eye disease is a clinical one that may be supported by tests. Thyroid function tests of free thyroxine, triiodothyronine, and thyroid stimulating hormone (TSH) should be measured. Autoantibodies that should be sought include antithryoglobulin, antimicrosomal, and antigastric parietal cell antibodies. In some instances thyroid stimulating antibodies (also known as TSH receptor antibodies) may be measured. Raised antibody levels support the diagnosis but are not conclusive. In the adjoining article, Professor Weetman reviews current knowledge about autoimmunity in this disorder. Enlarged extraocular muscles can be demonstrated by ultrasonography, preferably B-scan, and by computed tomography (CT).3 CT scans in the horizontal axis can occasionally mislead and views in the coronal plane, either direct or computer enhanced, give unequivocal crosssections of all the ocular muscles. Magnetic resonance imaging (MRI) has been claimed to give even better views of the orbital apex (fig 2) when evidence of optic nerve compression by the enlarged muscles is being sought. The absence of irradiation risks and hence the possibility of serial examinations may make MRI the method of choice if costs can be controlled. Incipient optic nerve compression is evidenced by falling visual acuity, reduced visual fields (but no generally agreed typical changes), relative afferent pupillary reaction defect, and altered colour vision with decreased colour contrast sensitivity along the tritan (blue) axis.4
Treatment
Surgical decompression When vision is threatened seriously by optic nerve compressionor the proptosis is so severe that corneal exposure is progressing to ulceration and endophthalmitis, surgical decompression is the method of choice.6,7 In addition to surgery for visual loss or jeopardised integrity of the globe, there is an increasing tendency for some surgeons to offer decompression for cosmetic reasons alone. As a minimum, the medial half of the orbital floor and the medial wall need to be breached to allow orbital fat under pressure
to escape into the antral and ethmoidal sinuses, respectively. There are different routes to achieve this end:
The last route gives best optic nerve decompression right up to the orbital apex. The orbital periosteum is opened with posterior-to-anterior longitudinal incisions over its distal half and with circumferential incisions anteriorly to allow the pressurised orbital fat to herniate out into the sinuses. This increased space for orbital contents gives an average 4-5 mm reduction in the exophthalmometer measurements. When even greater decompression is needed some surgeons include a third orbital wall-the lateral. Naffziger’s transfrontal route through the roof of the orbit is rarely used nowadays because of much higher morbidity than with the other routes. Solely cosmetic decompression may be done with the Tessier bicoronal scalp incision after the front third of the scalp has been shaved.8 As this wide skin flap is reflected forwards and downwards, the whole of the orbit may be exposed with access to all four walls if necessary. By whichever route, it is usual to decompress both sides at one operation since both are often affected but to different extents. Any of these methods may cause sensory changes in infraorbital nerve territory and some increased epiphora but both effects are normally temporary. All patients may have a worsening of their ocular movements, which become more esotropic, and often with an A-pattem-ie, worse on upgaze-which persists in some patients.
Symptomatic treatment Many patients have much
less yet substantial ocular involvement for which such drastic intervention is not needed. Artificial tear drops can be used to relieve irritable eyes—eg,
hypromellose (Hypromellose Eye-drops, BPC)
which can be used as often as required-in addition to a lubricant at night-eg, yellow soft paraffin (Simple Eye Ointment BP). If lid closure is incomplete, the lids can be taped on retiring. Broad tape (2-5 cm wide) is best applied from the side of the nose horizontally across the closed lids for most effective closure. Oedema fluid that collects in the lids overnight can be reduced by means of an extra pillow or if the head of the bed is raised on bricks. Other patients respond well to cyclopenthiazide (’Navidrex’ [Ciba, UK]), one or two 0’5 5 mg tablets, taken at bedtime. Double vision Patients with diplopia need careful orthoptic monitoring and help.2,9 The field of binocular single vision is recorded, as is the Hess chart, which shows the movements of each eye relative to its fellow eye. If the restriction of ocular movements is symmetrical and equal, the Hess chart can give the misleading impression that the eye movements are not too severe a problem. Additionally, the range of movements of each eye is recorded separately since this is a sensitive index of how eye movement is affected. To help the patient cope with double vision, he may be shown a compensatory head posture (if he has not already discovered this for himself). Other patients benefit from wearing Fresnel, plastic press-on prisms on their glasses. These
31
Fig 2-(Top) MRI horizontal scan through orbits and (bottom) coronal indicated by arrow on MRI scan.
section taken at level
MRI scan shows
proptosis with straightening of optic nerves and enlargement of the medialand lateral optic nerves in cross-section (long arrow), enlarged medial (short arrow) and inferior (middle length arrow) rectus muscles, together with the enlarged lateral and superior rectus muscles, are compressing the optic nerves at the orbital apex rectus muscles. Coronal section shows
can be changed easily at subsequent visits if the ocular restrictions are still changing. Only a few patients need temporary occlusion to block diplopia. The ocular movements are checked at 3-monthly intervals until the measurements confirm that they have been stable for 6 months, and then prisms (if not too strong) may be built into the spectacle lenses, or ocular muscle surgery may be done. Most commonly, a tight inferior rectus needs to be recessed; sometimes, the inferior recti and medial recti of both eyes may need surgery at one operation to restore at least a central area of binocular single vision. Under general anaesthesia the tight muscles are recessed; at least one of them is on a sliding suture, which can be adjusted to the optimum position the next morning under local anaesthesia (topical drops) with the help of the alert patient’s responses.1O Most surgeons undercorrect the restriction because the antagonist muscles have become very strong while working against tight muscles, and further changes in ocular muscle balance have to be allowed for as far as possible. Such an operation will mean that in some cases prisms are no longer needed or that the necessary prism is much weaker and easily incorporated into glasses.
prisms
Botulinum toxin When the patient’s ocular movement restriction is of only 12-18 months’ duration, earlier temporary relief may be given by an injection of botulinum A toxinllinto the affected muscle under local anaesthesia as an outpatient. It is thought
that the botulinum toxin cannot be working on established fibrosis but that it must be exerting its action by other means. Simonsz and Konunerell 12 have proposed recently that in the early stages, active muscle contraction and not fibrosis limits ocular rotations.12 The botulinum toxin "uncouples" this contraction by blocking neuromuscular transmission at the end plate. Even more surprisingly, in one out of six patients the effect of the toxin lasts much longer than the expected 2 months, but it is not possible to predict in which patients."
Medical decompression Patients
with moderate to pronounced ocular involvement, such as bilateral unequal proptosis and some diplopia, or evidence of incipient optic nerve compression be treated may medically. High-dose systemic
corticosteroids—eg, prednisolone 80-100 mg daily-have been used with some success to "medically decompress" the orbits.14 There is a high tendency to relapse as the steroid doses
are
reduced and often maintenance levels of 30 mg
a
day or more are needed. The medical consequences of prolonged steroid therapy are as unacceptable to some patients and physicians as is the disease. Cyclosporin alone has given equivocal results but is establishing a role when used in conjunction with a moderate dose of prednisone. 15 Intravenous methylprednisolone, Ig in 48 h, is effective" but should be used only with strict medical monitoring for inpatients. Plasmapheresis has also been used effectively but
32
the
subsequent
rebound effect
the use of workers have
necessitating
systemic steroids has meant that abandoned this procedure.
most
Radiotherapy During the past few years, radiotherapy has re-emerged as a most useful form of treatment; megavoltage, highly collimated
beams from a linear accelerator are lymphocytotoxic. The Stanford group have continued with this treatment since their 1973 paper17 and reported further results last year.18 The X-ray beam is aimed via a lateral port to give maximum dose to the retro-ocular tissues but at negligible risk to the lens and retina. These investigators found that a total 2000 cGy dose in 10 or 12 fractions over a 2-week period as an outpatient was most effective but male patients still on treatment for hyperthyroidism responded least well. A decrease in orbital tension, relieving optic nerve compression, and some decrease in proptosis and in conjunctival injection may be expected over the following 2 weeks to 3 months. Previous concern that orbital fibrosis would be increased by radiotherapy, making subsequent surgery to the ocular muscles more difficult, has proved to be unfounded. Like medical decompression by high-dose steroids, radiotherapy is most effective within the first year of onset of severe ocular changes. However, Mourits et a119 have recently suggested that it would be beneficial to identify periods of active orbital inflammation within the long natural history2O of the condition on the basis of painful ocular movements, tenderness, and increased conjunctival injection. They propose that immunosuppression by steroids or radiotherapy would be the most successful regimen during such times and should not be limited to within the first year of onset.
Lid surgery As soon as optic nerve compression has been controlled and diplopia relieved, any malposition of eyelids due to retraction of the upper or lower lid can be corrected.21 The lids are adjusted to the underlying globe and hence all ocular muscle surgery must have been completed. Persistent upper-lid retration for more than a year after any hyperthyroidism has been treated responds to disinsertion of the smooth muscle (Muller’s) component of the levator for up to 2 mm of exposed sclera. If greater than 2 mm, the levator aponeurosis should be incised at its borders also, or even recessed. Lower-lid retraction may follow inferior rectus recessions of more than 4 mm and this degree often has to be exceeded to correct severe hypotropia of the eye. Correction of the lower-lid covering is usually best done by incorporation of "spacers" of stored sclera between the lower border of the tarsal plate and the lower lid retractors. Lateral tarsorrhaphy is never done as an isolated procedure to contain increasing proptosis with chemosis because it is bound to fail. However, the procedure may be done as a final correction to give the best appearance at the same time that an upper lid retraction is being reduced for a mild inactive
proptosis. Conclusion As soon as any associated thyrotoxicosis has been controlled and care taken to avoid temporary episodes of hypothyroidism, any optic nerve compression must be treated by surgical decompression, radiotherapy, or systemic steroids. Persistent ocular movement limitations are corrected by ocular muscle surgery with prismatic
spectacle aid if necessary. Finally, the lids are adjusted to the globe for best appearance.22 Some surgeons feel confident enough to offer surgical decompression for cosmetic reasons alone for this very distressing condition. Whichever treatments are used it is rarely possible to restore either the ocular movements or the patient’s appearance to their original state. No preventive therapy is yet available, nor will it be until the pathogenesis is clarified. Meanwhile the physician has to use his limited means to deal with the various stages of orbital involvement and maintain the patient’s morale over several years with compassion and
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