STEREOACUITY DEVELOPMENT IN CHILDREN W I T H NORMAL BINOCULAR SINGLE VISION PAUL E. ROMANO, M.D.,
JUDITH A. ROM ANO, CO.,
AND JAMES E. PUKLIN,
M.D.
Chicago, Illinois
Stereoscopic vision is characterized by the visual perception of relative depth, not from monocular visual clues such as perspective, shadow, interposition or parallax, but rather from unique binocular visual clues, namely the symmetrical horizontal disparity of the position of retinal images of objects other than the object of regard, from correspond ing retinal points.1 Stereoscopic depth perception is not an "all or none" phenomenon since the ability to judge relative depth when monocular clues are excluded varies with monocular visual acuity, illumination, duration of stimuli, ab solute distance (threshold effect), size of the visual field,2 and may even improve with training.3 This relative ability is termed stereoscopic acuity1 or stereoacuity.4 Stereoacuity, more precisely, is the small est amount of horizontal retinal image dis parity that gives rise to a sensation of rela tive depth and is expressed as the visual angle (in seconds of arc) of this disparity. The normal value for stereoacuity according to Ogle1 is 20 seconds of arc (standard devia tion = 10 seconds of arc). Parks 4 considers normal stereoacuity to be 40 seconds of arc or better, based on clinical studies. Ogle's normal value plus two standard deviations (20 seconds + 2 X 10 seconds = 40 sec onds) coincides with Parks's upper limit of normalcy. When one attempts to apply this standard to the pediatrie age group, the problem of patient cooperation is compounded by a lack of information about the age at which full stereoacuity develops. From the Division of Ophthalmology, Children's Memorial Hospital, and the Department of Oph thalmology, Northwestern University Medical School, Chicago, Illinois. Reprint requests to Paul E. Romano, M.D., Chil dren's Memorial Hospital, 2300 N. Children's Plaza, Chicago, IL 60614.
General references provide little informa tion: Walsh and Hoyt 5 state that binocular vision with stereoscopic vision is firmly es tablished before the fifth year ; Parks 6 feels that normal fusion matures around the age of 7 years ; other studies are even less spe cific.7·8 Recent research established some land marks of stereoacuity development but the information is incomplete: Polak, Emde, and Spitz9 and Bower10 found gross stereoscopic depth perception in 2- and 3-month-old chil dren. At the other end of the developmental scale, Scott and Marsh 11 found that all school children (aged 9 to 13) with otherwise nor mal binocular single vision had 40 seconds of arc of stereoacuity or better. Hofstetter 12 and Jani 13 suggested an improvement in stereoacuity with advancing age but did not define it. (A decrease in stereoacuity begin ning in the fifth decade of life was also dem onstrated.14) Amigo" specifically studied ste reoacuity in a group of children aged 3 to 5 j ^ but he did not exclude children with strabis mus or poor vision in one or both eyes. Tatsumi and Tahira 1 " studied stereoacuity in normal children and adults. Their results, however, suggest the inclusion of individuals with abnormalities of binocular vision in both of their normal groups (only 86% of their normal adults and only 75% of their normal children in the 9- to 10-year-old age group achieved 40 seconds of arc or better). In addition, none of these authors indi cated that appropriate steps were taken to prevent the subjects from reading the test material on monocular clues. Except for Scott and Marsh's work,11 the failure to ex clude individuals with abnormalities of binoc ular vision in these studies makes the defin ing of standards for normal development in appropriate. Therefore, we attempted to determine
VOL. 79, NO. 6
STEREOACUITY
more precisely the development and improve ment in stereoacuity with advancing age in childhood, utilizing essentially normal chil dren with normal binocular single vision, de termined by factors other than stereoacuity, per se. MATERIALS AND METHODS
In this prospective study, we examined 321 children between the ages of \y2 and 13 years who represented a demographically balanced population. Thirteen children were examined more than once (at approximately three-month intervals) for a total of 344 de terminations. Children were included in the study only if they gave consistent evidence of normal binocular single vision compatible with their age level. Normal binocular single vision was present when the following con ditions were met: best corrected visual acuity for each eye equal and within normal limits for age; corneal light reflexes symmetrical, and full ductions and versions ; normal sen sory binocular cooperation on one or more tests at both distance and near including the cover test, the Worth 4-dot test, fusional am plitudes on the amblyoscope, and the 4-diopter prism test. We placed particular empha sis on the latter test and patients who had other than normal or atypical-1 responses were excluded from the study as having pos sible subtle abnormalities of binocular vi sion." Children with any medical condition that might influence the results of the ocular ex amination, such as concurrent illness, men tal retardation, or any debilitating condition or pathologic findings of the central nervous system, were excluded. No patient was in cluded who had an anisometropia of more than 1.0 diopter by spherical equivalent. Visual acuity was determined monocularly at 5 to 6 meters. We used linear Snellen optotypes, linear illiterate E's, or Allen cards,* depending on the subject's age. In the young est children, normal visual acuity could be »Preschool Vision Test, Henry F. Allen, M.D., Ophthalmix, 44 S. La Grange Rd., La Grange, IL 60525.
967
established only by a normal fixation pattern and the absence of pathologic ■findingsand refractive errors. The specific test used to determine stereo acuity was the standard Titmus Stereotest (utilizing Polaroid Vectographs and glasses). The best stereoacuity score possible on this test was 40 seconds of arc. We used the best available light in the room during stereoacuity measurement. In chil dren younger than about 5 years of age, no attempt was made to keep the test at the rec ommended 40-cm (16-inch) testing distance because the lack of verbal skills often pre cluded an interprétable response. The young er child was allowed to hold the test at arm's length to permit him to touch the correct circle or animal. (No correction was made for these stereoacuity scores achieved at a distance less than 40 cm.) To make sure that the score achieved was on binocular stereoscopic and not monocu lar clues, we turned the test or the spectacles upside down to invert (depress) the position of the usually elevated stereoscopic image. If the subject spontaneously perceived this change, or noted that stereoscopic elevation was no longer present, a valid endpoint was presumed. In the younger children, stereo acuity scores could not always be confirmed by this maneuver. RESULTS
Graphic representation of the data (Fig. 1 ) demonstrated a slow but steady improve ment in Titmus Stereotest stereoacuity scores from ages 2 to 9 after which a normal stereo acuity score of 40 seconds of arc was con sistently obtained. This pattern held true for the data obtained from single examinations on 308 children as well as for the multiple examinations over a period of several months to years of the remaining 13 children (Fig. 2). We converted the data to a form more suit able for clinical use, a bar graph (Fig. 3), using six-month intervals up to age 6 and then 12-month intervals. The data were fur-
AMERICAN JOURNAL OF OPHTHALMOLOGY
968 NONE I i ' »
3000
H
HH+-
I [lin H Hill I . 4-4-
JUNE, 1975
STEREOACUITY ^ AGE AT te METER * · (years) 321 NORMAL CHILDREN (344 Determinations)
i 800 Q
!
I S
400
H
H—III IH
300' 200'
-H—I-
III I I I
140'
oc 100 tu
Fig. 1 (Romano, Romano, and Puklin). Scattergram plot of Titmus Stereoacuity test scores for 321 children with normal binocular single vision by other factors. In 13 children, more than one determination was made at intervals of three months or more. There is a gradual improvement in scores with advancing age until age 9, after which a normal score of 40 seconds of arc is consistently obtained. Marks not di rectly on a line indicate a score on the nearest line. ther reduced for greater convenience in the Table by utilizing the lower limits of the bar graph (Fig. 3) for each age group. DISCUSSION
Where comparable, our study tends to con firm previous results. Amigo,15 using young er children, noted that none of 22 children in his study below age 4 achieved a stereoacuity better than 100 seconds. Tatsumi and Tahira 1 " found that nine of 66 children (15%) in this age group did better than 100 seconds while in our study, five of 87 such children (6%) did better than 100 seconds. Considering all children between the ages of 3 and 5τ/2, only two of Amigo's15 100 chil-
TABLE LOWER LIMITS OF STEREOACUITY ON TITMUS S T E R E O T E S T I N S U B J E C T S W I T H NORMAL
BINOCULAR SINGLE VISION
Age,* yrs 3|-5 5-5i 5è-6 6-7 7-9 Over 9
Stereoacuity, seconds of arc 3000 140 100 80 60 40
* Below 31 years of age, any measurable stereo acuity would support the presence of normal binocu lar single vision. However, the absence of a response to this test below age 3J must also be considered normal and cannot be construed to indicate defec tive binocular vision.
VOL. 79, NO. 6
969
STEREOACUITY
dren (2%) achieved 40 seconds: Tatsumi and Tahira 16 found that 11 of 78 such chil dren (14%) achieved 40 seconds. In our study, 13 of 87 such children ( 15%) achieved 40 seconds. In the older (9 to 13 years) age group, Scott and Marsh 11 found that all 101 subjects achieved 40 seconds of arc. Similarly, all 56 of our subjects achieved 40 seconds of arc. Tatsumi and Tahira, 18 however, found only 42 of 56 such children (75%) able to achieve a normal stereoacuity of 40 seconds of arc. The data obtained described the develop ment of stereoacuity (as measured by the Titmus Stereotest) in children who, by all other available factors, had normal binocular single vision.
The data might suggest that stereoscopic depth peception does not exist before 2 or 3 years of age. It is most unlikely that this is true since Polak, Emde, and Spitz9 and Bower10 convincingly demonstrated that stereoscopic depth perception is present in infancy. This discrepancy is probably due to the artificial depth representation of the Titmus test and the comprehension limitations of children below the ages of 2 or 3 years. Even a normal adult needs a few seconds (when performing the Titmus Stereotest for the first time) to comprehend precisely what he is expected to see and to overcome the psychologic barrier of perceiving a threedimensional image on what is obviously a flat surface. We would, therefore, not interpret
NONE
STEREOACUITY AT Va METER
3000
v
AGE (years)
13 NORMAL CHILDREN
« 800" 400 300' 5 200
S oc IÜ
140' 100'
6 1
2
1
3
4 5 AGE (Years)
β
7
8
9
10 t i 12 13
Fig. 2 (Romano, Romano, and Puklin). Titmus Stereoacuity test scores on 13 children with normal binocular single vision by other factors, tested more than once at intervals of three months or more. These individual cases demonstrate the same type of gradual improvement with advancing age as the group as a whole in Figure 1. The slightly steeper slope is probably the result of experience or training from multiple testings.
970
AMERICAN JOURNAL OF OPHTHALMOLOGY
JUNE, 1975
NONE | — p a
STEREOACUITY AGE VS. (years) AT te METER
3000"
321 NORMAL CHILDREN (344 Determinations) —50th Percentile — 75th Percentile
ω
ti \
4 * 5 * AGE (Years)
T 7
I I I I 10 11 12 13
Fig. 3 (Romano, Romano, and Puklin). These data are the same as in Figure 1, converted to a bar graph on half-year intervals to age 6, and yearly intervals thereafter, to facilitate clinical application. Alternately, the Table, taken from this graph, may also be used.
the absence of stereoacuity on the Titmus Stereotest below the ages of 2 or 3 as indi cating that the child does not have stereo scopic depth perception. On the contrary, he almost certainly does, but we are unable to measure it with this test because of the na ture of the test and the comprehension fac tor. The pattern of steady improvement noted from the first time a child is able to give a positive response to the test is probably not, however, a matter of comprehension. We do not know how much this developmental pat tern is the result of cortical area 19 develop ment (where stereoscopic appreciation of depth is supposed to take place). None of the other factors measured on examination seemed to correlate with this pattern of de velopment. Visual acuity increases with age
but the normal visual acuity of 3- and 4-yearolds (20/50 to 20/30) is sufficient to achieve a stereoacuity of 40 seconds of arc; hence, the development pattern cannot be explained on the basis of developing visual acuity. The data describing stereoacuity develop ment may be useful clinically: (1) Tests for stereoacuity can be useful screening devices to find gross as well as subtle abnormalities of binocular and monocular vision for any adults or children over the age of 3yi years. It may be useful in younger subjects, but only if a positive response is obtained. (2) Based on the expected stereoacuity for age, one may more accurately prognosticate in those types of strabismus where a variable degree of sensory binocular cooperation is present (such as intermittent exotropia or esotropia, monofixation syndromes). (3) Based on the
STEREOACUITY
VOL. 79, NO. 6
expected stereoacuity for age, one may assess the sensory results of strabismus therapy at an early age. SUMMARY
We made 344 stereoacuity determinations (Titmus Stereotest) on 321 children, ages \y2 to 13 years, who had normal binocular single vision tested by other factors. The data showed a gradual improvement in stereoacu ity scores with increasing age—up to age 9— when a normal stereoacuity of 40 seconds of arc was consistently found. The lower limits of stereoacuity compatible with normal binoc ular single vision were 3j4 years, 3,000 sec onds; 5 years, 140 seconds; 5% years, 100 seconds ; 6 years, 80 seconds ; 7 years, 60 sec onds ; and 9 years, 40 seconds. REFERENCES
1. Ogle, K. N. : Researches in Binocular Vision. New York, Hafner, 1964, pp. 133-141, 274. 2. Luria, S. M. : Stereoscopic and resolution acu ity with various fields of view. Science 164:452, 1969. 3. Wittenberg, S. : The effect of training on stereoscopic acuity. Am. J. Optom. 46:645, 1969. 4. Parks, M. M. : Stereoacuity as an indicator of bifixation. In Arruga, A. (ed.) : Strabismus Sym posium. Basel, Karger, 1968, pp. 258-260.
971
5. Walsh, F. B., and Hoyt, W. F. : Clinical NeuroOphthalmology, 3rd ed. Baltimore, Williams and Wilkens, 1969, p. 139. 6. Parks, M. M. : Growth of the eye and develop ment of vision. In Liebman, S. D., and Gellis, S. S. (eds.) : The Pediatrician's Ophthalmology. S t Louis, C. V. Mosby, 1966, pp. 15-25. 7. Duke-Elder, S., and Wybar, K. : Ocular Motility and Strabismus. In Duke-Elder, S. (ed.): System of Ophthalmology, vol. 6. St. Louis, C. V. Mosby, 1973, pp. 400-411. 8. Ophthalmologic Staff of the Hospital for Sick Children, Toronto : The Eye in Childhood. Chicago, Yearbook Medical Publishers, 1967, pp. 1-78. 9. Polak, P. R., Emde, R. N., and Spitz, R. A.: The smiling response. 2. Visual discrimination and the onset of depth perception. J. Nerv. Ment. Dis. 139:407, 1964. 10. Bower, T. G. R. : The object in the world of the infant Sei. Am. 225:30, 1971. 11. Scott, W. E., and Marsh, J. : Stereoacuity in normal individuals. Ann. Ophthalmol. 6:99, 1974. 12. Hof stetter, H. : Absolute threshold measure ments with diastereo test. Arch. Soc. Am. Oftalmol. Optom. 6:327, 1968. 13. Jani, S. W. : The age factor in stereopsis screening. Am. J. Optom. 43:653, 1966. 14. Bell, B., Wolf, E., and Bernholz, B. A.: Depth perception as a function of age. Aging and human development. 3:77, 1972. 15. Amigo, G. : Pre-school vision study. Br. J. Ophthalmol. 57:125, 1973. 16. Tatsumi, S., and Tahira, K. : Study on the stereotest (Titmus). Folia Ophthalmol. Jap. 23:620, 1972. 17. Romano, P. E., and von Noorden, G. K. : Atypical responses to the 4-diopter prism test. Am. J. Ophthalmol. 67:935, 1969.
JUDITH A. ROM ANO, CO.,
AND JAMES E. PUKLIN,
M.D.
Chicago, Illinois
Stereoscopic vision is characterized by the visual perception of relative depth, not from monocular visual clues such as perspective, shadow, interposition or parallax, but rather from unique binocular visual clues, namely the symmetrical horizontal disparity of the position of retinal images of objects other than the object of regard, from correspond ing retinal points.1 Stereoscopic depth perception is not an "all or none" phenomenon since the ability to judge relative depth when monocular clues are excluded varies with monocular visual acuity, illumination, duration of stimuli, ab solute distance (threshold effect), size of the visual field,2 and may even improve with training.3 This relative ability is termed stereoscopic acuity1 or stereoacuity.4 Stereoacuity, more precisely, is the small est amount of horizontal retinal image dis parity that gives rise to a sensation of rela tive depth and is expressed as the visual angle (in seconds of arc) of this disparity. The normal value for stereoacuity according to Ogle1 is 20 seconds of arc (standard devia tion = 10 seconds of arc). Parks 4 considers normal stereoacuity to be 40 seconds of arc or better, based on clinical studies. Ogle's normal value plus two standard deviations (20 seconds + 2 X 10 seconds = 40 sec onds) coincides with Parks's upper limit of normalcy. When one attempts to apply this standard to the pediatrie age group, the problem of patient cooperation is compounded by a lack of information about the age at which full stereoacuity develops. From the Division of Ophthalmology, Children's Memorial Hospital, and the Department of Oph thalmology, Northwestern University Medical School, Chicago, Illinois. Reprint requests to Paul E. Romano, M.D., Chil dren's Memorial Hospital, 2300 N. Children's Plaza, Chicago, IL 60614.
General references provide little informa tion: Walsh and Hoyt 5 state that binocular vision with stereoscopic vision is firmly es tablished before the fifth year ; Parks 6 feels that normal fusion matures around the age of 7 years ; other studies are even less spe cific.7·8 Recent research established some land marks of stereoacuity development but the information is incomplete: Polak, Emde, and Spitz9 and Bower10 found gross stereoscopic depth perception in 2- and 3-month-old chil dren. At the other end of the developmental scale, Scott and Marsh 11 found that all school children (aged 9 to 13) with otherwise nor mal binocular single vision had 40 seconds of arc of stereoacuity or better. Hofstetter 12 and Jani 13 suggested an improvement in stereoacuity with advancing age but did not define it. (A decrease in stereoacuity begin ning in the fifth decade of life was also dem onstrated.14) Amigo" specifically studied ste reoacuity in a group of children aged 3 to 5 j ^ but he did not exclude children with strabis mus or poor vision in one or both eyes. Tatsumi and Tahira 1 " studied stereoacuity in normal children and adults. Their results, however, suggest the inclusion of individuals with abnormalities of binocular vision in both of their normal groups (only 86% of their normal adults and only 75% of their normal children in the 9- to 10-year-old age group achieved 40 seconds of arc or better). In addition, none of these authors indi cated that appropriate steps were taken to prevent the subjects from reading the test material on monocular clues. Except for Scott and Marsh's work,11 the failure to ex clude individuals with abnormalities of binoc ular vision in these studies makes the defin ing of standards for normal development in appropriate. Therefore, we attempted to determine
VOL. 79, NO. 6
STEREOACUITY
more precisely the development and improve ment in stereoacuity with advancing age in childhood, utilizing essentially normal chil dren with normal binocular single vision, de termined by factors other than stereoacuity, per se. MATERIALS AND METHODS
In this prospective study, we examined 321 children between the ages of \y2 and 13 years who represented a demographically balanced population. Thirteen children were examined more than once (at approximately three-month intervals) for a total of 344 de terminations. Children were included in the study only if they gave consistent evidence of normal binocular single vision compatible with their age level. Normal binocular single vision was present when the following con ditions were met: best corrected visual acuity for each eye equal and within normal limits for age; corneal light reflexes symmetrical, and full ductions and versions ; normal sen sory binocular cooperation on one or more tests at both distance and near including the cover test, the Worth 4-dot test, fusional am plitudes on the amblyoscope, and the 4-diopter prism test. We placed particular empha sis on the latter test and patients who had other than normal or atypical-1 responses were excluded from the study as having pos sible subtle abnormalities of binocular vi sion." Children with any medical condition that might influence the results of the ocular ex amination, such as concurrent illness, men tal retardation, or any debilitating condition or pathologic findings of the central nervous system, were excluded. No patient was in cluded who had an anisometropia of more than 1.0 diopter by spherical equivalent. Visual acuity was determined monocularly at 5 to 6 meters. We used linear Snellen optotypes, linear illiterate E's, or Allen cards,* depending on the subject's age. In the young est children, normal visual acuity could be »Preschool Vision Test, Henry F. Allen, M.D., Ophthalmix, 44 S. La Grange Rd., La Grange, IL 60525.
967
established only by a normal fixation pattern and the absence of pathologic ■findingsand refractive errors. The specific test used to determine stereo acuity was the standard Titmus Stereotest (utilizing Polaroid Vectographs and glasses). The best stereoacuity score possible on this test was 40 seconds of arc. We used the best available light in the room during stereoacuity measurement. In chil dren younger than about 5 years of age, no attempt was made to keep the test at the rec ommended 40-cm (16-inch) testing distance because the lack of verbal skills often pre cluded an interprétable response. The young er child was allowed to hold the test at arm's length to permit him to touch the correct circle or animal. (No correction was made for these stereoacuity scores achieved at a distance less than 40 cm.) To make sure that the score achieved was on binocular stereoscopic and not monocu lar clues, we turned the test or the spectacles upside down to invert (depress) the position of the usually elevated stereoscopic image. If the subject spontaneously perceived this change, or noted that stereoscopic elevation was no longer present, a valid endpoint was presumed. In the younger children, stereo acuity scores could not always be confirmed by this maneuver. RESULTS
Graphic representation of the data (Fig. 1 ) demonstrated a slow but steady improve ment in Titmus Stereotest stereoacuity scores from ages 2 to 9 after which a normal stereo acuity score of 40 seconds of arc was con sistently obtained. This pattern held true for the data obtained from single examinations on 308 children as well as for the multiple examinations over a period of several months to years of the remaining 13 children (Fig. 2). We converted the data to a form more suit able for clinical use, a bar graph (Fig. 3), using six-month intervals up to age 6 and then 12-month intervals. The data were fur-
AMERICAN JOURNAL OF OPHTHALMOLOGY
968 NONE I i ' »
3000
H
HH+-
I [lin H Hill I . 4-4-
JUNE, 1975
STEREOACUITY ^ AGE AT te METER * · (years) 321 NORMAL CHILDREN (344 Determinations)
i 800 Q
!
I S
400
H
H—III IH
300' 200'
-H—I-
III I I I
140'
oc 100 tu
Fig. 1 (Romano, Romano, and Puklin). Scattergram plot of Titmus Stereoacuity test scores for 321 children with normal binocular single vision by other factors. In 13 children, more than one determination was made at intervals of three months or more. There is a gradual improvement in scores with advancing age until age 9, after which a normal score of 40 seconds of arc is consistently obtained. Marks not di rectly on a line indicate a score on the nearest line. ther reduced for greater convenience in the Table by utilizing the lower limits of the bar graph (Fig. 3) for each age group. DISCUSSION
Where comparable, our study tends to con firm previous results. Amigo,15 using young er children, noted that none of 22 children in his study below age 4 achieved a stereoacuity better than 100 seconds. Tatsumi and Tahira 1 " found that nine of 66 children (15%) in this age group did better than 100 seconds while in our study, five of 87 such children (6%) did better than 100 seconds. Considering all children between the ages of 3 and 5τ/2, only two of Amigo's15 100 chil-
TABLE LOWER LIMITS OF STEREOACUITY ON TITMUS S T E R E O T E S T I N S U B J E C T S W I T H NORMAL
BINOCULAR SINGLE VISION
Age,* yrs 3|-5 5-5i 5è-6 6-7 7-9 Over 9
Stereoacuity, seconds of arc 3000 140 100 80 60 40
* Below 31 years of age, any measurable stereo acuity would support the presence of normal binocu lar single vision. However, the absence of a response to this test below age 3J must also be considered normal and cannot be construed to indicate defec tive binocular vision.
VOL. 79, NO. 6
969
STEREOACUITY
dren (2%) achieved 40 seconds: Tatsumi and Tahira 16 found that 11 of 78 such chil dren (14%) achieved 40 seconds. In our study, 13 of 87 such children ( 15%) achieved 40 seconds. In the older (9 to 13 years) age group, Scott and Marsh 11 found that all 101 subjects achieved 40 seconds of arc. Similarly, all 56 of our subjects achieved 40 seconds of arc. Tatsumi and Tahira, 18 however, found only 42 of 56 such children (75%) able to achieve a normal stereoacuity of 40 seconds of arc. The data obtained described the develop ment of stereoacuity (as measured by the Titmus Stereotest) in children who, by all other available factors, had normal binocular single vision.
The data might suggest that stereoscopic depth peception does not exist before 2 or 3 years of age. It is most unlikely that this is true since Polak, Emde, and Spitz9 and Bower10 convincingly demonstrated that stereoscopic depth perception is present in infancy. This discrepancy is probably due to the artificial depth representation of the Titmus test and the comprehension limitations of children below the ages of 2 or 3 years. Even a normal adult needs a few seconds (when performing the Titmus Stereotest for the first time) to comprehend precisely what he is expected to see and to overcome the psychologic barrier of perceiving a threedimensional image on what is obviously a flat surface. We would, therefore, not interpret
NONE
STEREOACUITY AT Va METER
3000
v
AGE (years)
13 NORMAL CHILDREN
« 800" 400 300' 5 200
S oc IÜ
140' 100'
6 1
2
1
3
4 5 AGE (Years)
β
7
8
9
10 t i 12 13
Fig. 2 (Romano, Romano, and Puklin). Titmus Stereoacuity test scores on 13 children with normal binocular single vision by other factors, tested more than once at intervals of three months or more. These individual cases demonstrate the same type of gradual improvement with advancing age as the group as a whole in Figure 1. The slightly steeper slope is probably the result of experience or training from multiple testings.
970
AMERICAN JOURNAL OF OPHTHALMOLOGY
JUNE, 1975
NONE | — p a
STEREOACUITY AGE VS. (years) AT te METER
3000"
321 NORMAL CHILDREN (344 Determinations) —50th Percentile — 75th Percentile
ω
ti \
4 * 5 * AGE (Years)
T 7
I I I I 10 11 12 13
Fig. 3 (Romano, Romano, and Puklin). These data are the same as in Figure 1, converted to a bar graph on half-year intervals to age 6, and yearly intervals thereafter, to facilitate clinical application. Alternately, the Table, taken from this graph, may also be used.
the absence of stereoacuity on the Titmus Stereotest below the ages of 2 or 3 as indi cating that the child does not have stereo scopic depth perception. On the contrary, he almost certainly does, but we are unable to measure it with this test because of the na ture of the test and the comprehension fac tor. The pattern of steady improvement noted from the first time a child is able to give a positive response to the test is probably not, however, a matter of comprehension. We do not know how much this developmental pat tern is the result of cortical area 19 develop ment (where stereoscopic appreciation of depth is supposed to take place). None of the other factors measured on examination seemed to correlate with this pattern of de velopment. Visual acuity increases with age
but the normal visual acuity of 3- and 4-yearolds (20/50 to 20/30) is sufficient to achieve a stereoacuity of 40 seconds of arc; hence, the development pattern cannot be explained on the basis of developing visual acuity. The data describing stereoacuity develop ment may be useful clinically: (1) Tests for stereoacuity can be useful screening devices to find gross as well as subtle abnormalities of binocular and monocular vision for any adults or children over the age of 3yi years. It may be useful in younger subjects, but only if a positive response is obtained. (2) Based on the expected stereoacuity for age, one may more accurately prognosticate in those types of strabismus where a variable degree of sensory binocular cooperation is present (such as intermittent exotropia or esotropia, monofixation syndromes). (3) Based on the
STEREOACUITY
VOL. 79, NO. 6
expected stereoacuity for age, one may assess the sensory results of strabismus therapy at an early age. SUMMARY
We made 344 stereoacuity determinations (Titmus Stereotest) on 321 children, ages \y2 to 13 years, who had normal binocular single vision tested by other factors. The data showed a gradual improvement in stereoacu ity scores with increasing age—up to age 9— when a normal stereoacuity of 40 seconds of arc was consistently found. The lower limits of stereoacuity compatible with normal binoc ular single vision were 3j4 years, 3,000 sec onds; 5 years, 140 seconds; 5% years, 100 seconds ; 6 years, 80 seconds ; 7 years, 60 sec onds ; and 9 years, 40 seconds. REFERENCES
1. Ogle, K. N. : Researches in Binocular Vision. New York, Hafner, 1964, pp. 133-141, 274. 2. Luria, S. M. : Stereoscopic and resolution acu ity with various fields of view. Science 164:452, 1969. 3. Wittenberg, S. : The effect of training on stereoscopic acuity. Am. J. Optom. 46:645, 1969. 4. Parks, M. M. : Stereoacuity as an indicator of bifixation. In Arruga, A. (ed.) : Strabismus Sym posium. Basel, Karger, 1968, pp. 258-260.
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