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British Journal of Ophthalmology, 1981, 65, 727-735 Development of visual acuity in infants with congenital cataracts S. G. JACOBSON,* I. MOHINDRA, AND R. HELD From Massachusetts Institute of Technology, Department of Psychology, Cambridge, Massachusetts, and *Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA SUMMARY The visual acuity of 4 infants with congenital cataracts was measured serially during the first year of life by a preferential looking technique. Two infants with bilateral cataracts and no measurable acuity before surgery showed rapid development of acuity to normal levels for age after surgery and optical correction. In an infant with a unilateral cataract and an infant with a cataract and persistent hyperplastic primary vitreous marked differences in monocular acuities were found after surgery. Acuities became equal in the latter case after occlusion of the normal eye, while the other infant recovered acuity with 'bi-ocular' viewing. These acuity measurements demonstrate the sensitivity of the human visual system to binocular and monocular visual form deprivation in the first year of life. Clinical experience and results from studies of visual deprivation in young animals' emphasise the need for early surgery and optical correction in infants with congenital cataracts. Advances in surgical techniques and contact lens practice have permitted therapy to be initiated within the first weeks, if not days, of life. However, the visual results of this early treatment are rarely known until after age 2 or 3 years when visual acuity can first be measured with conventional methods. Before this age acuity is usually estimated by assessment of physical signs (e.g., strabismus, nystagmus, clarity of ocular media, and fundus appearance) and by observing the infant's response to a light, striped drum or other large visual target. The adequacy of postoperative optical correction is assumed from retinoscopic findings rather than actually determined by a measure of acuity. Just as in the routine care of older children and adults with cataracts, it would be valuable to quantitate the visual acuity of infants with congenital cataracts before and after surgery and during visual rehabilitation with spectacle or contact lenses. The only previous reports of such a series of measure- ments are by Enoch and Rabinowicz' and Enoch et al.6 In these studies optokinetic nystagmus was Correspondence to Professor Richard Held, Massachusetts Institute of Technology, Department of Psychology, 79 Amherst Street, Cambridge, Ma 02139, USA. used to assess acuity in infants with unilateral cataracts. The 'preferential looking technique' is a simple and reliable psychophysical method that has been used to study the development of visual acuity in normal infants.7'-0 We have now applied this tech- nique in a clinical setting, and in the present study we report the results of serial measurements of visual acuity during the first year of life in 4 infants with congenital cataracts, 2 with bilateral and 2 with unilateral cataracts. Subjects and methods The 4 infants in the present study were patients of ophthalmologists at the Massachusetts Eye and Ear Infirmary, Boston. Before their referral for visual acuity testing and frequently thereafter they had full ophthalmological examinations. At each session for visual acuity testing the infants received a brief eye examination including assessment of ocular motility, retinoscopy, and evaluation of ocular media and fundus appearance by direct or indirect ophthal- moscopy. Cataract surgery was performed on all of them with a 2-instrument technique of irrigation and aspiration-cutting with the O'Malley ocutome. 1 The surgeons attempted to remove all the lens material at the time of the first surgery. Keratometry and/or contact lens fitting with trial lenses were usually accomplished under anaesthesia in the early post- 727 on July 13, 2020 by guest. Protected by copyright. http://bjo.bmj.com/ Br J Ophthalmol: first published as 10.1136/bjo.65.10.727 on 1 October 1981. Downloaded from

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  • British Journal of Ophthalmology, 1981, 65, 727-735

    Development of visual acuity in infants with congenitalcataractsS. G. JACOBSON,* I. MOHINDRA, AND R. HELD

    From Massachusetts Institute of Technology, Department ofPsychology, Cambridge, Massachusetts, and*Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA

    SUMMARY The visual acuity of 4 infants with congenital cataracts was measured serially during thefirst year of life by a preferential looking technique. Two infants with bilateral cataracts and nomeasurable acuity before surgery showed rapid development of acuity to normal levels for age aftersurgery and optical correction. In an infant with a unilateral cataract and an infant with a cataractand persistent hyperplastic primary vitreous marked differences in monocular acuities were foundafter surgery. Acuities became equal in the latter case after occlusion of the normal eye, while theother infant recovered acuity with 'bi-ocular' viewing. These acuity measurements demonstrate thesensitivity of the human visual system to binocular and monocular visual form deprivation in thefirst year of life.

    Clinical experience and results from studies of visualdeprivation in young animals' emphasise the needfor early surgery and optical correction in infants withcongenital cataracts. Advances in surgical techniquesand contact lens practice have permitted therapy tobe initiated within the first weeks, if not days, of life.However, the visual results of this early treatment arerarely known until after age 2 or 3 years when visualacuity can first be measured with conventionalmethods. Before this age acuity is usually estimatedby assessment of physical signs (e.g., strabismus,nystagmus, clarity of ocular media, and fundusappearance) and by observing the infant's response toa light, striped drum or other large visual target. Theadequacy of postoperative optical correction isassumed from retinoscopic findings rather thanactually determined by a measure of acuity.

    Just as in the routine care of older children andadults with cataracts, it would be valuable toquantitate the visual acuity of infants with congenitalcataracts before and after surgery and during visualrehabilitation with spectacle or contact lenses. Theonly previous reports of such a series of measure-ments are by Enoch and Rabinowicz' and Enochet al.6 In these studies optokinetic nystagmus was

    Correspondence to Professor Richard Held, Massachusetts Instituteof Technology, Department of Psychology, 79 Amherst Street,Cambridge, Ma 02139, USA.

    used to assess acuity in infants with unilateralcataracts. The 'preferential looking technique' is asimple and reliable psychophysical method that hasbeen used to study the development ofvisual acuity innormal infants.7'-0 We have now applied this tech-nique in a clinical setting, and in the present study wereport the results of serial measurements of visualacuity during the first year of life in 4 infants withcongenital cataracts, 2 with bilateral and 2 withunilateral cataracts.

    Subjects and methods

    The 4 infants in the present study were patients ofophthalmologists at the Massachusetts Eye and EarInfirmary, Boston. Before their referral for visualacuity testing and frequently thereafter they had fullophthalmological examinations. At each session forvisual acuity testing the infants received a brief eyeexamination including assessment of ocular motility,retinoscopy, and evaluation of ocular media andfundus appearance by direct or indirect ophthal-moscopy. Cataract surgery was performed on all ofthem with a 2-instrument technique of irrigation andaspiration-cutting with the O'Malley ocutome.1 Thesurgeons attempted to remove all the lens material atthe time of the first surgery. Keratometry and/orcontact lens fitting with trial lenses were usuallyaccomplished under anaesthesia in the early post-

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  • S. G. Jacobson, l. Mohindra, and R. Held

    operative course; further refittings were performedwith the infant awake.A fast version of the 2-alternative forced-choice

    preferential looking technique was used to measurevisual acuity. Details of the technique and measuresof its reliability and validity have been publishedelsewhere.9 Briefly, the technique is based on thediscovery that given a choice between a patterned andan unpatterned target, an infant prefers to look at thepatterned one. The infant sits on the parent's lap50 cm from a black partition containing 2 screens.Back projected on to one screen is a high-contrast,vertically-orientated, square-wave grating, and onthe other screen is a homogeneous field of the samemean luminance (34 cd/M2). An observer unaware ofthe side of presentation of the grating is seated behindthe partition and watches the infant's eye and/or headmovements through a peephole. The observer judgeswhich side the infant prefers to look at, and, if thisjudgment coincides with the side of presentation ofthe grating, the infant is considered to have made acorrect response. The side of presentation of gratingsis randomised, and gratings are presented in a stair-case from low to high spatial frequencies, that is, fromcoarse to fine. (Spatial frequency is the number ofcycles of a grating, i.et., pairs of black and whitestripes per degree of visual angle subtended.) Thissequence of gratings always began with 0-38 cyclesper degree (c/d), progressed in one-octave steps to1-5 c/d and thereafter in approximately 1/2-octavesteps to 24 c/d. (An octave change is a doubling orhalving of spatial frequency.) Sessions were ter-minated when a spatial frequency was reached atwhich the infant fixated the homogeneous field moreoften than the grating (criteria defined in Gwiazdaet al.9). The spatial frequency one step lower on thestaircase than this termination frequency was taken asthe threshold or 'visual acuity'. Fig. 5 providesexamples of staircases obtained using the 'fast pro-cedure' and how such results compare with thosefrom a constant stimulus method (see Results ofinfants B and C for details.Monocular acuities were measured by a disposable

    patch occluder over the eye not being tested. Theaphakic eyes of the infants were corrected duringtesting with either contact lenses (hard or soft) orspectacles. Correction was always 'overplussed' byapproximately 2 dioptres and therefore focused forthe testing distance. All thresholds reported foraphakic eyes have been corrected for magnificationdue to the spectacle or contact lenses. 12

    Results

    Figs. 1-4 show the results of serial measurements ofvisual acuity in the 4 infants. In all figures visual acuity

    is plotted on the vertical axis in spatial frequency andage along the horizontal axis in weeks. For readersunfamiliar with visual resolution thresholds ex-pressed in spatial frequency approximate equivalentsin Snellen notation are plotted on the right verticalaxis of each graph (convention being 6/6 Snellen=30 c/d7). Development of visual acuity in normalinfants as measured with the current method wouldbe expected to proceed from about 0 50 c/d (approxi-mately 6/360) at 1 month of age to 12 c/d (approxi-mately 6/15) at 1 year of age.'0 Clinical details andvisual acuity measurements will be discussed for eachof the 4 infants.

    CASE IInfant A was noted to have bilateral cataracts at 3days of age. There was no family history of congenitalcataracts, and all investigations to determine theaetiology of the cataracts were inconclusive. Onexamination the corneas were 10 mm in diameter,pupils reactive, and there was no nystagmus orstrabismus. The infant would not fix or follow a light.There were dense nuclear lenticular opacities in botheyes, with a red reflex around the edge of theopacities in the dilated pupil. Fundus detail wasobscured by the cataracts, and ultrasonographyrevealed only the lenticular opacities.

    Visual acuity measurements in both eyes pre-operatively showed no responses to the lowest spatialfrequency grating presented, that is, acuity worsethan 0-38 c/d (Fig. 1). Cataract surgery was per-formed on the right eye at age 3 weeks, and the ocularmedia were clear enough to discern fundus detail onexamination 1 week postoperatively. Visual acuity ofthe right eye measured at 51/2 weeks was 1-8 c/d, whilethe acuity of the left eye was still not measurable.Cataract surgery on the left eye was performed at age6 weeks. Some hyphaema was present immediatelyafter operation, and the view of the fundus one weeklater was moderately clear, obscured only slightly bysome opacification on the intact posterior capsule ofthe lens. Hard contact lens wear was started at age 7weeks, and visual acuity measured one day later was4-0 c/d for the right eye and 1-35 c/d for the left eye.Over the next 3 weeks visual acuity increased in botheyes until it reached 8-1 and 4-0 c/d in right and lefteyes respectively. The ocular media of the right eyewere clear, but some pupillary membrane was notedin the left eye by age 10 weeks. Further measurementsof visual acuity at age 22 weeks were unchanged and aslight increase in acuity of both eyes was present atage 261/2 weeks, the right eye being 10-8 and the lefteye 5-4 c/d (these results were replicated twice foreach eye in this session).A discission of the pupillary membrane in the left

    eye was attempted at age 27 weeks. Despite an

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  • Development of visual acuity in infants with congenital cataracts

    Fig. 1 Visual acuity developmentin an infant with bilateral congenitalcataracts. RE, right eye; LE, lefteye; BE, both eyes; NM, notmeasurable (i. e., acuity worse than0-38 cld). Snellen acuities along theright vertical axis are approximateequivalents to the measured gratingthresholds in spatialfrequency onthe left vertical axis. Arrows alongthe horizontal axis indicate ageswhen surgery was performed.

    apparently satisfactory opening in the membrane atthe time of surgery, several days later the openingappeared small, eccentric to the visual axis, andunquestionably inadequate. Visual acuities measuredabout 4 weeks after this unsuccessful surgery (age 31weeks) showed a profound difference between the 2eyes: right eye 13X5 c/d and left eye 1-35 c/d (resultsreplicated twice). By age 35 weeks the acuity of theleft eye had decreased further to 034 c/d, while theright eye acuity was now 10-8 c/d. A membranectomywas performed in the left eye with the O'Malleyocutome at age 41 weeks. One day postoperativelythe left eye showed no response even to the lowestspatial frequency grating despite clear ocular media.This measurement was repeated 3 times during thissession with the same result. Visual acuity of the righteye was higher now than previously-16 c/d. Oneweek later occlusion of the right eye as therapy for theasymmetry in acuities was started at 5 hours per day.At 441/2 weeks of age acuity of the right eye haddecreased to 5 4 c/d, while that of the left eye hadincreased to 1-8 c/d. This trend of decreasing acuity inthe right eye and increasing acuity in the left eyecontinued until age 471/2 weeks, when acuities hadreversed. The right eye at 4-0 c/d was now 2 octaves

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    lower than the left eye at 16 c/d. Occlusion therapywas then decreased, and it was eventually stoppedentirely. By age 50 weeks acuities were equal; botheyes were 10;8 c/d, which is normal for this age.

    CASE 2

    Infant B was born with the rubella syndrome andbilateral congenital cataracts characterised by someopacification apparently in the nucleus of the lens anda clear zone in the lens periphery. Corneal diameterswere 8 mm, and there was no nystagmus or stra-bismus. A full fundus examination was limited bythe lens opacities and pupils which would not dilatebeyond the mid position, but there were good redreflexes and grossly normal posterior poles. Duringthe first weeks of life the infant's pupils were kept asdilated as possible with topical atropine, andbinocular visual acuity measured at 5 weeks of agewas 1-5 c/d (Fig. 2). By 71/2 weeks of age acuity hadincreased to 3-0 c/d. At age 9 weeks acuity decreasedslightly to 2-25 c/d, and within a fortnight the lenseshad become totally opaque. Eye movements becamewandering and dysconjugate, and a variable angleesotropia with nystagmus developed. At this time andthereafter until cataract surgery there were no

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    Fig. 2 Visual acuity developmentin an infant with the rubellasyndrome and bilateral congenitalcataracts.

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  • S. G. Jacobson, I. Mohindra, and R. Held

    responses to even the lowest spatial frequencygratings presented when acuity measurements wereattempted.

    Medical approval for general anaesthesia was notgiven until age 24 weeks, and cataract surgery thenwas performed on the right eye. At the end of surgerythere was a clear view of the fundus, and a typicalappearance of rubella retinopathy was present.Visual acuity of the right eye measured 3 days post-operatively (with clear ocular media) was 2-7 c/d,while the left eye still showed no measurableresponses. Results of acuity measurements of theright eye on the 6th and 7th postoperative days (age25 weeks) and at 281/2 weeks of age all had the samethreshold-4 0 c/d. Spectacle correction was given tothe infant for full-time wear beginning at 27 weeks ofage.

    Cataract surgery was performed on the left eye at281/2 weeks of age, and, with clear ocular media 3 dayspostoperatively, visual acuity of this eye was 2-7 c/d.Over the next few weeks visual acuity of the right eyeincreased to 9 0 c/d, while acuity of the left eyeremained at 2-7 c/d. The right eye subsequentlydecreased in acuity while the left eye increased. Atage 40 weeks soft contact lenses were fitted and womcontinuously thereafter. Acuities at 41 weeks of agewere equal at 5;4 c/d, and by 54 weeks of age, theywere 10-8 c/d, which is normal for this age. The infantremains esotropic with alternating fixation and somenystagmus.At age 66 weeks we had the opportunity to measure

    at the same testing session the visual acuity of the lefteye twice with the 'fast procedure' and also with aconstant stimulus method (Fig. 5, left-hand graphs).For this latter method gratings ranging from 1-5 to18 c/d were presented in randomised sequence. Therewere at least 20 trials for each of the 8 spatial fre-quencies presented. The lower left graph in Fig. 5shows the psychometric function resulting from these

    Fig. 3 Visual acuity developmentin an infant with a unilateralcongenital cataract.

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    data; percentage positive responses are plottedagainst spatial frequency in this graph. The threshold(70% frequency of seeing) for the constant stimulusmethod was between 6-0 and 9-0 c/d, while boththresholds when the fast procedure was used were 9-0c/d. This represents at most about a 1/2 octave differ-ence between results obtained with the method usedin this study and the more conventional method ofconstant stimuli.

    CASE 3Infant C was noted to have a cataract in the right eyeat 5 days after birth. No cause for the cataract couldbe discovered. The comeal diameter of both eyes was10 mm, pupils were equal and reactive, and theanterior segment of the right eye was normal. Thelenticular opacity in the right eye was dense centrally,with a clear zone peripherally. Ultrasonographyrevealed only the cataract. There was no strabismus,but on occlusion of the normal left eye the infantwould not fix or follow a light with the right eye.

    Visual acuity of the left eye at I11/2 weeks of agewas 4-5 c/d, while the right eye showed no responsesto even the lowest spatial frequencies presented (Fig.3). Cataract surgery was performed at this time, and aview of the fundus immediately after surgery revealedno abnormalities. The media were clear 2 days post-operatively, and visual acuity measured in the righteye was the same as preoperatively, that is, withoutresponses to the coarsest gratings presented. Acuityof the left eye was again 4 5 c/d. At 12/2 weeks of ageacuity of the right eye had increased to 0-34 c/d(replicated twice in this session) and by 171/2 weeks itwas 2-0 c/d. When the test on the right eye wasrepeated one hour later the result was 1-4 c/d, repre-senting only about a 1/2 octave difference between the2 thresholds. Visual acuity of the left eye was now12 c/d. A 'continuous-wear' soft contact lens was thenplaced on the right eye and within one week, visual

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  • Development ofvisual acuity in infants with congenital cataracts

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    acuity of this eye increased to 6-3 c/d, while the lefteye remained at 12 c/d. This contact lens becameill-fitting and was noted to be decentered at timesduring the day. Visual acuity was measured at age 21weeks (with a different contact lens), when the righteye was 4-2 c/d and the left eye, 9-0 c/d. The ill-fittingcontact lens had to be continued for a further 21/2weeks for lack of availability of another lens. Threedays before the next acuity testing session (at age 231/2weeks) the lens was lost. At this session acuity of theright eye was found to have decreased further to 2-0c/d (replicated 2 days later), while the left eye was 12c/d. Another soft lens was placed at this time, andwithin 5 days the acuity of the right eye had increasedto 8-1 c/d. Eventually this soft lens also had to bereplaced, this time by a hard lens. By 27 weeks theinfant was wearing the hard lens for 12 hours eachday, and acuities for right and left eyes were 10-8 and9-0 c/d respectively. Monocular acuities measured at29, 32, 35, 40, and 45 weeks of age were within oneoctave difference of one another.At 47 weeks of age the acuity of the right eye was

    measured by both the fast procedure and a constantstimulus method (see similar testing performed oninfant B for details). As shown in Fig. 5 (right-handgraphs), the results with the 2 methods were nearlyidentical, both being approximately 9-0 c/d.

    CASE 4

    Infant D was noted at birth to have a cataract in theright eye, and the diagnosis of persistent hyperplasticprimary vitreous was made about one month later. At11 weeks of age lensectomy and vitrectomy wereperformed. A retinal detachment was discovered

    postoperatively, and treatment with cryopexy wasattempted without success. The retina then devel-oped a 1800 giant tear, and the patient was referred toBoston for further therapy. At age 13 weeks surgerywas performed and the retina was successfully re-attached by an 'open-sky' technique.'3 Subsequentexaminations under anaesthesia revealed a clearcornea, attached retina, some vitreous membranesadherent to the optic nerve head with traction, but agrossly normal-appearing macula except for somepigmentary changes. At age 31 weeks a contact lenswas fitted, and it was worn continuously thereafter.No constant strabismus was noted on manyexaminations.

    Visual acuity was measured at 32 weeks of age andwas 0-34 c/d (Fig. 4). The normal left eye had anacuity of 9-0 c/d. This 4-octave difference betweeneyes was unchanged when measurements wererepeated at 34 weeks of age. To decide on the visualpotential of the right eye constant occlusion of the lefteye was started at this time. The parents reported thatthe infant was irritable for 2 days after occlusion wasstarted but then behaved normally for the next 7 dayswhile using the right eye only. After a total of 9 daysof occlusion acuities were measured; the right eye hadincreased to 4-0 c/d, while the left eye had decreasedto 3-0 c/d. Repeat acuity measurements on the samevisit were 2-7 c/d and 2-2 c/d for right and left eyesrespectively (about a 1/2 octave difference betweenthe 2 sets of results). It is noteworthy that on removalof the occluder the left eye was esotropic and theinfant was fixing with the right eye. Occlusion wasstopped at this testing session, and on the next day theeyes were straight and acuities were measured once

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  • S. G. Jacobson, L. Mohindra, and R. Held

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    Fig. 5 Comparison between results obtained at the sametesting session by the fast procedure ofmeasuring acuity(method 1) and a constant stimulus method (method 2). Theleft-hand graphs arefrom infant B (left eye), while those onthe right are from infant C (right eye). In both infants formethod I responses to the038 cid andO-75 cidgratings wereall correct, although not displayed. Arrows along thehorizontal axis indicate the thresholds.

    again. Again the right eye was 4-0 c/d and the left eye3-0 c/d.At 38 weeks of age, 3 weeks after occlusion had

    been stopped, the right eye acuity had decreased to067 c/d while the left eye acuity had increased to18 c/d. Constant occlusion of the left eye was againprescribed, and after 7 days of occlusion acuity of theright eye was 2-7 c/d and that of the left eye 4-5 c/d(both measurements repeated twice in this sessionwith the same results). Again the parents described aperiod of irritability in the infant after onset ofocclusion (about 2 days), but normal behaviour soonfollowed. Occlusion was discontinued, and on thenext day acuities were measured and the same resultswere obtained as on the previous day.

    Discussion

    In the present study we used a preferential lookingtechnique to measure visual acuity in the first year oflife of infants with congenital cataracts. Manyvariants of this psychophysical technique have been

    used in recent years to study the development ofvisual acuity in normal infants, and there has beengood agreement of results from different teams ofinvestigators.7 Measurements with this methodindicate that visual resolution is limited at birth andincreases during the first year of life. Similar trends inacuity development have been found by other tech-niques such as optokinetic nystagmus or the visualevoked cortical potential, although absolute acuitylevels -differ with different methods.7 Dobson andTeller7 recently summarised the literature on normalinfant acuity and concluded that the increase in acuityin postnatal life as demonstrated with preferentiallooking, optokinetic nystagmus and visual evokedpotential methods probably reflects the neuralmaturation of the visual pathway. The patterns ofresults in the 4 infant patients of the present study arein striking contrast to the normal data. In the dis-cussion that follows these results are used to commenton the effects of visual deprivation in human infantsand the clinical management of infants with con-genital cataracts. An underlying assumption in thisdiscussion is that our psychophysical measurementsreflect neural abnormalities in the developing visualsystem of these infants. The validity of this assump-tion, as well as the patterns of results themselves, willobviously need to be confirmed by studying moreextensive series of patients with similar and differenttechniques and with longitudinal follow-up beyondthe first year of life.

    Binocular visual form deprivation occurred in in-fants A and B. In infant A this deprivation can beconsidered to have extended from birth until about 7weeks of age. In the first 3 weeks deprivation was dueto the cataracts; in the next 3 weeks, between opera-tions, the right eye was aphakic without correctionand the left eye phakic with cataract; and there was afurther week of bilateral aphakia before opticalcorrection was started. The first measured acuities inthe right eye and left eye after the respective opera-tions were nearly equal, and there was rapiddevelopment of acuity thereafter. The persistentdifference in acuities between the 2 eyes throughoutthe first months of life can probably be attributed toless clear ocular media in the left eye due to earlyhyphaema and developing pupillary membrane. Twoother infants with bilateral congenital cataracts, thesame timing of operation (3 and 6 weeks of age), anduncomplicated early postoperative courses have beenreported as showing rapid early acuity developmentin both eyes without any persistent interocular differ-ence in acuity as in infant A.14 It can be concludedthat a period of binocular form deprivation from birthuntil about 2 months of age certainly had no long-lasting detrimental effects on the development ofacuity.

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  • Development of visual acuity in infants with congenital cataracts

    Infant B had about 15 weeks of binocular formdeprivation beginning at age 3 months. The depriva-tion, however, was preceded by some early visualexperience with a recorded increase in acuity. Withindays of the operation for cataract acuity in the righteye was found to be nearly identical with the highestacuity attained before onset of deprivation. The firstmeasured acuity of the left eye after operation wassimilar to that first measured in the right eye. Aftersome inequality of monocular acuities, with the righteye higher than left (probably due to the short periodof optical correction afforded to the right eye beforeoperation on the left eye), acuities became equal anddeveloped to the level expected in normal infants at 1year of age. This pattern of results suggests that theperiod of binocular form deprivation only arrestedthe development of acuity. An apparent arrest ofdevelopment has also been noted in acuity measure-ments obtained on another infant with bilateralcataracts reported by Mohindra et al.'4 Cataractswere present in this infant from birth until about16 weeks of age, and acuities after surgery werelow and more like those of a much younger infant.After operations and optical correction therewas a gradual increase in acuity to levels normal forage.

    Direct comparison of these results with those ofexperimental studies of binocular visual deprivationis difficult because of the different modes of depriva-tion, relatively longer periods of deprivation inanimals, and the usual problem of species differences.It is of interest, however, that prolonged bilateraloptical blur during development, such as could occurin congenital cataracts or subsequent uncorrectedaphakia, has been shown experimentally'5 to de-crease the spatial resolution of individual sustained-type geniculate neurons in cats. The question ofrecovery from binocular deprivation has been con-sidered by Timney et al. 6 Gradual and nearly com-plete development of acuity in kittens was found evenafter 4 or 6 months of dark-rearing, an extreme formof binocular deprivation. These behavioural resultsand other physiological results,'7 like our findings inhuman infants with bilateral cataracts, lend them-selves to the interpretation that binocular deprivationmay simply delay the development of vision. How-ever, a more complex mechanism also must occur,since clinical experience and experimental evidence'6suggest that the longer the deprivation the lessrecovery is possible.Monocular form deprivation occurred in infants A,

    C, and D and caused marked differences in acuitybetween eyes. The pupillary membrane in infant Adeprived the left eye over a period of months. Whenthe membrane was finally removed, there was nomeasurable acuity in the deprived eye and at least 5

    octaves difference in acuities between eyes. Similarly,infant C had no measurable acuity postoperatively inthe right eye after 11 weeks of monocular form depri-vation from a unilateral cataract, and there was a3-octave difference in monocular acuities. Infant Dhad about 7 months of monocular deprivation, in-itially due to lens and vitreous opacities and latercontributed to by post-surgical eyelid oedema, prob-able corneal irregularity, and uncorrected aphakia.There were responses only to the lowest spatial fre-quency when acuity of the deprived eye was firstmeasured, and more than 4 octaves difference inacuities was present between eyes. Two types of re-covery from these effects of monocular deprivationwere documented. Firstly, recovery in infants A andD occurred as a result of reversing the deprivation,that is, occlusion of the previously open eye while theformerly deprived eye remained unoccluded. Thereverse occlusion in infant A was part-time (5 hoursper day), while constant occlusion was prescribed forinfant D. The effect of reverse occlusion was toincrease the acuity of the previously deprived eye atthe expense of the acuity of the eye now beingdeprived. This 'trade-off' in acuities has also beenreported in strabismic infants undergoing monocularocclusion as therapy for acuity differences.'8 Theincrease in acuity of the right eye of infant A between6 and 9 months of age, during the decrease in the lefteye acuity secondary to the pupillary membrane,probably represents another example of a trade-off.The different time courses of recovery with reversedeprivation-over days in infant D and over weeks ininfant A-seem to relate to the amount of occlusionused (i.e., constant versus part-time). The secondmode of recovery that occurred is exemplified in thedata from infant C. Full recovery of acuity in thedeprived eye occurred simply by leaving both eyesopen-so-called 'binocular recovery' or 'bi-ocularrecovery'. Jacobson et al. 9 also noted this form ofrecovery in a strabismic infant who had markedlydifferent acuities resulting from prolonged occlusiontherapy.

    In the only other prospective studies of visualdevelopment in infants with unilateral cataract Enochand Rabinowiczs and Enoch et al.6 reported acuitiesmeasured serially in 2 infants using an optokineticnystagmus technique. One infant had cataractsurgery at 4 days of age and showed gradual increasein acuity of both eyes over a period of nearly 4months. Another infant had cataract surgery at 6months of age, and again, over some 4 months, acuityof the affected eye increased steadily. The normalfellow eye in both these infants underwent part-timeocclusion. Despite differences in method of acuityassessment, timing of surgery, and use of occlusion inthe normal eye there are general similarities in the

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  • S. G. Jacobson, I. Mohindra, and R. Held

    pattern of acuity development in these 2 infants andin infant C.Monocular deprivation by eyelid suture in animals,

    including primates, provides an experimentalanalogue to these human data. In animals monoculardeprivation during the 'sensitive period' of develop-ment causes profound changes in visual corticalphysiology and morphology, lateral geniculatenucleus cell size, and behavioural acuity (seereviews 122). The degree and time course of recoveryhave been investigated by reverse suture tech-niques-that is, opening the deprived eye andsuturing the lids of the other-the counterpart of theocclusion therapy in infants A and D. In the kittenphysiological and morphological recovery can occurin a matter of days after reverse suture begins,23 24 atime course very similar to that seen in infant D.'Bi-ocular recovery' such as occurred in infant C alsohas been demonstrated in kittens by serial measure-ments of visual acuity25 and by physiological record-ings in the visual cortex.26

    Despite the small sample of patients reported inthis study the available data allow for certain com-ments to be made about management of infantpatients with congenital cataracts. Timing of the op-eration and optical correction is acknowledged to beof great importance in the treatment of both bilateraland unilateral congenital cataracts. '6 InfantA and 2other infants with bilateral cataracts'4 were operatedon at 3 and 6 weeks of age and underwent opticalcorrection at least by 8 weeks of age. All 3 infantsshowed development of visual acuity which rapidlyattained levels normal for age. Although final adultacuities are not known for these infants, the presentdata suggest that surgical intervention before 3 and 6weeks of age may be unnecessary. How long surgerycan be delayed is a more difficult issue. The resultsfrom infant B and the infant with bilateral cataractsuntil 16 weeks of age reported by Mohindra et al. 4seem to indicate that successful surgery and prompt,careful optical correction even as late as 4 or 6 monthsof age is still compatible with acuity development tolevels normal for age in the first year of life. Thetiming of surgery in infant C, our only example of anuncomplicated unilateral cataract, was relatively latecompared to reports of surgery within days of birth.5Yet, even though surgery was performed at I 1/2weeks of age and optical correction started at 171/2weeks, acuity development in the deprived eye wasrapid, and both eyes became nearly equal by 27 weeksof age. These early visual results for infant C areespecially encouraging in view of the dismal prognosisusually assigned to such cases. About 3 months of ageis therefore not too late to begin therapy for unilateralcongenital cataract, although earlier therapeuticintervention might in theory be preferable.

    The importance of proper optical correction inpatients with congenital cataract has been stressed byEnoch et al.6 Infant C provides an example of theneed for constant and scrupulous attention to thismatter. Since occlusion of the normal eye was notused in this infant and there was no strabismus,increases and decreases in acuity of the deprived eyeafter surgery were most likely due to the effect ofoptical quality on development of spatial resolution.After an early increase in acuity, an ill-fitting, de-centered contact lens led to a decrease in acuitybetween 18 and 231/2 weeks of age. Only after 2changes of contact lenses was an adequate fitobtained, and thereafter acuity began to increaseagain.The clinical value of occlusion therapy is especially

    well illustrated in the data from infant D. Constantmonocular occlusion for 9 days equalised widelydifferent acuities resulting from 7 months ofmonocular deprivation. Once occlusion was stopped,a rebound occurred; acuity in the affected right eyedecreased while acuity in the normal left eye in-creased again. This strong preference for the left eyeis understandable in view of the right eye's poorerimage quality, probable restricted visual field, andprobable organic maculopathy. The effectiveness ofpart-time occlusion is seen in the results of infant Aafter membranectomy. In addition the rapidity withwhich an undesired reversal of acuities can occurduring occlusion therapy is illustrated in the data fromthis infant. There is no question but that during mon-ocular occlusion therapy in the first year of lifefrequent assessments are essential. Finally, it isworthy of clinical attention that occlusion of thenormal eye was not necessary to permit recovery ofthe affected eye in infant C. The infant visual systemis capable therefore of recovering acuity after mon-ocular deprivation when input to the 2 eyes has beenequalised. However, a close monitoring of visualacuity development is imperative if 'bi-ocularrecovery' is to be used in the management of suchpatients.

    In conclusion, the feasibility of making serialmeasurements of visual acuity in infants with con-genital cataracts has been demonstrated. Althoughastute clinicians in the past have successfully treatedsuch patients without knowing visual acuities, thereshould be little argument that having this informationcan only lead to better understanding and bettermanagement of these patients. These data also con-tribute to our increasing knowledge of the effects ofmonocular and binocular visual form deprivation onthe very plastic visual system of the human infant.

    We thank Miss A. E. Stromberg, Dr S. J. Fricker. and ProfessorC. H. Dohlman for their help and encouragement throughout this

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  • Development of visual acuity in infants with congenital cataracts

    study. We are especially grateful to Dr E. Mobilia for fitting andproviding contact lenses for the infants and to Dr T. Hirose, Dr A . R.Bellows, Dr J. Zwaan, and Dr D. Walton for the privilege of testingtheir patients. This work was supported by grants from the NationalInstitutes of Health (no. EY-02649 and no. EY-02621) and from theSpencer Foundation (no. LTR-DTD-71373).

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