Modulation of amblyopia therapy following early surgery for unilateral congenital cataracts.

BACKGROUND--Stimulus deprivation amblyopia is the principal cause of visual impairment in infants with unilateral congenital cataract. Even if lensectomy is undertaken at an early age, intensive postoperative occlusion of the phakic eye is essential for the development of useful vision in the aphakic eye. Despite this, the optimum method of regulating occlusion therapy is uncertain. METHODS--Interocular acuity differences identified using clinical preferential looking techniques (Keeler cards) were used to regulate target levels of phakic eye occlusion in a prospective evaluation of 10 systemically, metabolically, and neurologically normal infants in whom dense unilateral cataract was diagnosed before 8 weeks of age, and operated upon by 10 weeks. Actual occlusion levels were recorded each day by parents in a diary. The development of preferential looking acuity in the phakic and aphakic eye were compared with prediction intervals derived from observations on 43 normal children. RESULTS--Aphakic eye preferential looking acuities were within the normal range at last review in all but one infant. Interocular acuity differences were < or = 0.5 octave in all children older than 1 year of age at last review, and > or = 1 octave in three of four children less than 1 year old at last review (Fisher exact p = 0.033). Phakic eye acuities were within the normal range in all infants at all visits. CONCLUSION--Within the first 2 years of life, normal preferential looking acuity may be achieved in both eyes of infants undergoing early surgery for unilateral congenital cataract if occlusion therapy is modulated according to interocular acuity differences quantified by clinical preferential looking techniques.     

Amblyopia in the phakic eye after unilateral congenital cataract extraction

The treatment of unilateral congenital cataract remains a challenge because form deprivation early in life leads to amblyopia. Visual outcomes after congenital cataract extraction have improved dramatically with earlier surgery, greater attention to optical correction of the aphakia, and part-time occlusion therapy of the phakic eye. A published review of unilateral congenital cataract studies between 1988 and 2004 found that 88% of patients with primary intraocular lens implantation achieved 20/200 or better visual acuity and a mean of 20% achieved 20/40 or better visual acuity. Improved outcomes are attributable, in part, to surgical intervention at an earlier age. It has been shown that surgical intervention during the first 6 weeks of age is associated with a better visual prognosis than surgery at a later age. In this report, we describe a patient with unilateral congenital cataract treated with cataract extraction and intraocular lens implantation at 8 weeks of age who had a better visual outcome in his operative eye than in his phakic eye.     

Real-time rapid acuity assessment using VEPs: development and validation of the step VEP technique

PURPOSE: To develop a reference range of visual acuities corresponding to thresholds found using the step VEP method of rapid, objective visual acuity assessment by using steady state (ss)VEPs in normal adults. METHODS: Sixteen normal adults had visual acuity assessed five times with both the step VEP and with Glasgow Acuity Cards (GAC). Subjects were tested once without filters and with four different levels of optical filtering provided by Bangerter neutral-density filters. Acuity outcomes were compared by linear regression and Bland-Altman analysis. RESULTS: Step VEP and GAC acuities correlated highly (r(2) = 0.60, P = 0.000). GAC scores were predicted with the equation: acuity(GAC) = (0.9 x acuity(step VEP)) - 0.37. Step VEP acuity was 0.46 (95% CI: -0.13 to 1.06) logMAR units greater (poorer) than GAC acuities in these normal subjects. The disparity between test results did not vary with visual acuity. CONCLUSIONS: The step VEP provides a rapid, objective means of estimating visual acuity that can be related to acuity derived from a commonly used letter test.     

A comparison of the performance of three visual evoked potential-based methods to estimate visual acuity

Purpose

To compare visual acuities estimated by three methods of visual evoked potential (VEP) recordings to those obtained by two subjective measures [ETDRS and FrACT (Freiburg acuity test)].

Methods

Ten healthy subjects, aged between 26 and 67 years (mean 43.5), were examined. Best-corrected acuity determined by the ETDRS was between 0.03 and ?0.3 logMAR (mean ?0.06). Sweep VEPs (sweepVEP), pattern appearance VEPs (pappVEP) and steady-state VEPs (ssVEP) were recorded with two electrode placements (10–20 and Laplace) with best optical correction and with artificially degraded vision using five Bangerter occlusion foils, reducing acuity to about 0.1, 0.22, 0.52, 0.7 and 1.0 logMAR (0.8, 0.6, 0.3, 0.2 and 0.1 decimal scale). Two runs were performed.

Results

ETDRS and FrACT acuities showed good agreement, even though ETDRS seemed to underestimate acuity compared with FrACT at higher acuities. Laplace derivation did not improve any of the VEP-estimated acuities over the 10–20. SweepVEP tended to overestimate lower FrACT acuities, but showed good repeatability. PappVEP placed FrACT acuities into correct or neighboring categories in 87 % of cases. Average ssVEP acuity showed little difference to those of FrACT but variance was larger. ROC analysis for typical clinical application showed good performance for all three methods.

Conclusions

The two subjective measurements of acuities are well correlated. Under the conditions of our experiment, sweepVEP results were less variable and had a better repeatability than ssVEP acuities, whose analysis, in contrast to sweepVEP, can be automated. PappVEP estimates, however, offer a viable alternative, that is, quicker but of lower performance regarding the detection of low acuity thresholds. All methods had a good performance regarding minimum acuity detection if an average of two runs is used.     

Visual acuity and binocular vision in children with pseudophakia

PURPOSE: To evaluate the results of cataract surgery in children with IOL implantation. MATERIALS AND METHODS: Our research involved 106 children (156 eyes) with congenital and traumatic cataract, in age from 18 months to 18 years, who underwent cataract surgery with intraocular lens implantation. We evaluated visual acuity for far vision and binocular vision after surgery. RESULTS: Visual acuity over 0.5 in unilateral congenital cataract was found in 27.25%, in traumatic cataract in 73%, whereas in bilateral congenital cataract visual acuity over 0.5 we received in 75% of operated children. Full binocular vision was obtained in children with good visual acuity (0.5 and more), with appropriate alignment of the eyes: 13.1% in unilateral congenital cataract, 45.4% in traumatic cataract and 55% in congenital bilateral cataract. CONCLUSIONS: Cataract surgery with intraocular lens implantation results in increase of visual acuity and in achievement binocular vision, if surgery is carried out in the early period, after it had been diagnosed.     

Development of visual acuity in infants with congenital cataracts.

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 monouclar visual form deprivation in the first year of life.     

Simultaneous recording of visual evoked potentials and electroretinograms in patients with unilateral opaque media

We studied the correlation between preoperative visual evoked potentials (VEPs) and postoperative visual acuities in patients with unilateral opaque media. The fellow eye was used as the control. The filtering effect due to opaque media could be assessed on the basis of the difference of the electroretinogram (ERG) threshold in the two eyes. 'Modified VEPs' were then calculated by eliminating the assessed filtering effects, which improved our ability to detect the potential for visual recovery. In the normal eye, the stimulus threshold for VEP is lower than that for ERG by 2 or 3 log units. Therefore should a higher stimulus threshold be found for VEP than ERG, severe optic nerve damage is highly probable in eyes with media opacties.     

Predicting potential acuities in amblyopes

PURPOSE: Amblyopic patients, or their parents, often want to know the potential for success before committing to treatment. Recent reports have indicated that the pattern visual evoked potential (pVEP) can be used as a predictor of the success of amblyopia therapy. Unfortunately, these studies did not determine if acuity estimates from pVEPs could accurately predict the acuity post-treatment. Furthermore, pVEPs are not always practical to obtain because of the time necessary to acquire the data. Sweep VEPs (sVEP) offer the advantage of rapidly estimating visual acuity in amblyopic patients. In this retrospective study, the relationship between sVEP acuities measured pre-amblyopic therapy and Snellen acuities measured post-amblyopic therapy was determined. METHODS: Seventeen patients with amblyopia were studied. Monocular sVEP and Snellen acuities were determined pre-amblyopic therapy and Snellen acuities were determined post-amblyopic therapy. An Enfant 4010 computer system was used to produce the stimuli, record the VEPs, and extrapolate the acuity. The stimuli were horizontally oriented, sine wave gratings (11 spatial frequencies from 2 to 24 cpd) with a contrast of 80%, counterphased at 7.5 Hz. Standard VEP recording techniques were employed. Therapy consisted of the full refractive correction and occlusion combined with active vision therapy. RESULTS: The patients demonstrated a significant improvement in pre- to post-amblyopic therapy Snellen acuities (P < 0.00001). The intraclass correlation coefficient (r (i)) between the pre-therapy sVEP acuities and the post-therapy Snellen acuities was 0.73. A paired t-test did not find a significant difference between the two sets of data (P = 0.94). For the amblyopes in this study, the average difference (+/-SD) in the sVEP acuity estimate and the final Snellen visual acuity was +0.002 +/- 0.123 logMAR acuity lines. CONCLUSION: The results indicate that pre-amblyopic therapy sVEP acuity can be a good predictor of post-amblyopic therapy Snellen acuity.     

Monocular and binocular reading performance in children with microstrabismic amblyopia

AIM: To evaluate if functionally relevant deficits in reading performance exist in children with essential microstrabismic amblyopia by comparing the monocular and binocular reading performance with the reading performance of normal sighted children with full visual acuity in both eyes. METHODS: The reading performance of 40 children (mean age 11.6 (SD 1.4) years) was evaluated monocularly and binocularly in randomised order, using standardised reading charts for the simultaneous determination of reading acuity and speed. 20 of the tested children were under treatment for unilateral microstrabismic amblyopia (visual acuity in the amblyopic eyes: logMAR 0.19 (0.15); fellow eyes -0.1 (0.07)); the others were normal sighted controls (visual acuity in the right eyes -0.04 (0.15); left eyes -0.08 (0.07)). RESULTS: In respect of the binocular maximum reading speed (MRS), significant differences were found between the children with microstrabismic amblyopia and the normal controls (p = 0.03): whereas the controls achieved a binocular MRS of 200.4 (11) wpm (words per minute), the children with unilateral amblyopia achieved only a binocular MRS of 172.9 (43.9) wpm. No significant differences between the two groups were found in respect of the binocular logMAR visual acuity and reading acuity (p>0.05). For the monocular reading performance, significant impairment was found in the amblyopic eyes, whereas no significant differences were found between the sound fellow eyes of the amblyopic children and the control group. CONCLUSION: In binocular MRS, significant differences could be found between children with microstrabismic amblyopia and normal controls. This result indicates the presence of a functionally relevant reading impairment, even though the binocular visual acuity and reading acuity were both comparable with the control group.     

Treatment of bilateral refractive amblyopia in children three to less than 10 years of age

PURPOSE: To determine the amount and time course of binocular visual acuity improvement during treatment of bilateral refractive amblyopia in children three to less than 10 years of age. DESIGN: Prospective, multicenter, noncomparative intervention. METHODS: One hundred and thirteen children (mean age, 5.1 years) with previously untreated bilateral refractive amblyopia were enrolled at 27 community- and university-based sites and were provided with optimal spectacle correction. Bilateral refractive amblyopia was defined as 20/40 to 20/400 best-corrected binocular visual acuity in the presence of 4.00 diopters (D) or more of hypermetropia by spherical equivalent, 2.00 D or more of astigmatism, or both in each eye. Best-corrected binocular and monocular visual acuities were measured at baseline and at five, 13, 26, and 52 weeks. The primary study outcome was binocular acuity at one year. RESULTS: Mean binocular visual acuity improved from 0.50 logarithm of the minimum angle of resolution (logMAR) units (20/63) at baseline to 0.11 logMAR units (20/25) at one year (mean improvement, 3.9 lines; 95% confidence interval [CI], 3.5 to 4.2). Mean improvement at one year for the 84 children with baseline binocular acuity of 20/40 to 20/80 was 3.4 lines (95% CI, 3.2 to 3.7) and for the 16 children with baseline binocular acuity of 20/100 to 20/320 was 6.3 lines (95% CI, 5.1 to 7.5). The cumulative probability of binocular visual acuity of 20/25 or better was 21% at five weeks, 46% at 13 weeks, 59% at 26 weeks, and 74% at 52 weeks. CONCLUSIONS: Treatment of bilateral refractive amblyopia with spectacle correction improves binocular visual acuity in children three to less than 10 years of age, with most improving to 20/25 or better within one year.     

Vision in the "good" eye of children treated for unilateral congenital cataract.

PURPOSE: The authors examined linear acuity and contrast sensitivity in the "good" (fellow) eye of children treated for unilateral congenital cataract to determine (1) whether there were subtle deficits like those described for the good eye of patients with strabismic amblyopia and (2) whether any deficits were related to the degree to which the good eye had been patched. METHODS: The authors tested patients treated for unilateral congenital cataract who had a well-documented history of patching. The good eye was physically normal with minimal refractive error. The measures were linear acuity at far (n = 15) and contrast sensitivity (n = 9). RESULTS: Compared with age-matched control subjects, the good eyes of patients had subtle deficits in linear acuity and in contrast sensitivity at high spatial frequencies. These deficits occurred even in eyes that had received minimal patching, and their severity was not related systematically to the duration of patching, which varied widely across the group. CONCLUSION: The visual sensitivity of the good eye of children treated for unilateral congenital cataract is, on average, slightly reduced, even in cases of minimal patching. Consequently, any deficits discovered after aggressive patching may not have been caused by occlusion amblyopia.     

Binocular summation in visual evoked cortical potential in patients who have significantly different P100 peak latencies in their two eyes

Purpose To determine whether binocular summation in visual evoked cortical potential (VEP) is present in patients who have significantly different P100 peak latencies in their two eyes.Methods Twelve patients with unilateral optic neuritis (ON) and 11 normal controls were studied. All of them had visual acuity of 20/20 in both two eyes and good stereoacuity. Transient and steady-state VEPs were recorded with monocular and binocular pattern-reversal stimulation.Results In normal controls, the binocular summation ratio was 1.05 with transient stimulation and 1.21 with steady-state stimulation, and in ON patients it was 1.19 and 1.30, respectively. In ON patients, the peak latency of P100 components was delayed significantly when the affected eye was stimulated, but with binocular stimulation the waveform was very similar to that when the fellow eye was stimulated.Conclusion Binocular summation of VECP is not present in ON cases with large differences in the peak latency between the two eyes even if they have good stereoacuity. Binocular summation may not be correlated with stereopsis in adults whose binocular function has already matured.     

个性化多焦点人工晶状体植入术的初步临床研究

目的 探讨超声乳化白内障吸除联合双眼分别植入衍射型与折射型多焦点人工晶状体(MIOL)术后的视觉质量,评价CustomMatch个性化搭配模式的可行性.方法 前瞻性研究.将年龄相笑性白内障患者分为MIOL组与单焦点人工晶状体(SIOL)组符10例,行超声乳化白内障吸除联合人工晶状体(IOL)植入术.MIOL组为主视眼植入ReZoom NXGl IOL,对侧眼植入Tecnis ZM900 IOL;SIOL组为同期双眼植入Sensar AR40e IOL.观察患者术后不同光照条件下的远、中、近距离视力、阅读视力和阅读速度、焦点深度以及问卷调查.采用析因设计的方差分析,两两比较采用ISD检验.结果 术后1个月观察发现,在100 cd/m~2和6 cd/m~2光照度下,MIOL组患者可获得满意的双眼裸眼远视力和最佳矫正远视力.100 cd/m~2时,MIOL组在40 cm、63 am和100 cm的裸眼视力均在0.63以上,显著高于SIOL组(P=0.000);6 cd/m~2时,MIOL组在100 cm时的双眼裸眼视力与SIOL组比较差异无统计学意义(P=0.360),在63 cm和40 cm时显著高于SIOL组(P=0.000).在明、暗光线下MIOL组患者的裸眼阅读视力和阅读速度显著高于SIOL组(P=0.000,0.000),与SIOL组矫正后的阅读能力比较,差异没有统计学意义.MIOL组的焦点深度可达5.5D,其在中、近距离工作和阅读时的脱镜率可达70%(7/10).结论 CustomMatch个性化搭配模式在一定范围内可给白内障术后患者提供良好的全程视力.     

Artiflex toric phakic intraocular lens implantation in congenital nystagmus

Case

A 44-year-old woman with congenital nystagmus and myopic astigmatism in both eyes who was submitted to phakic intraocular lens (pIOL) implantation.

Methods

Full ophthalmologic examination including refractive status, corrected (CDVA) and uncorrected (UCVA) monocular and binocular visual acuities, ocular motility, slit-lamp evaluation, tonometry and fundoscopy before and after implantation of toric pIOLs (Artiflex; Ophtec BV, The Netherlands) in both eyes.

Results

Preoperative logMAR CDVA were 0.699 and 0.420 in the right and left eye, respectively. Three months after surgery, logMAR UCVA were 0.398 and 0.182, reaching binocular logMAR UCVA of 0.132. There were no changes in nystagmus characteristics after surgery.

Conclusions

pIOL implantation may be a safe and suitable treatment to correct high refractive errors in patients with congenital nystagmus. Significant improvement in CDVA and UCVA can be achieved.Key Words: Nystagmus, Refractive surgery, Toric phakic intraocular lens     

VEP analysis methods in children with optic nerve hypoplasia: relationship to visual acuity and optic disc diameter

Purpose

Assessing vision in young children with optic nerve hypoplasia (ONH) is challenging due to multi-directional infantile nystagmus, the range of optic nerve loss, and cognitive delay. This study examined visual evoked potential (VEP) responses and averaging techniques in children with ONH. The assumption is that EEG epochs with inconsistent temporal phase would be associated with nystagmus, signal reduction due to axon loss, and visual inattention.

Methods

A retrospective chart review was performed on 44 children (average age 2.2 years; SD 1.9). Optic disc diameter was estimated by ophthalmoscopy. Visual function was measured under binocular viewing and then compared to the eye with the larger optic disc to exclude secondary amblyopia. Visual acuity was measured by Teller cards or by recognition optotypes, and both measures were converted into log minimum angle of resolution (logMAR). VEPs were recorded to onset/offset of horizontal gratings and to reversing checkerboards. Signal-to-noise ratios (SNRs) were estimated from phase consistency across epochs in the Fourier domain. VEPs were also averaged after (1) correction of epochs for phase shifts across a limited bandwidth, or (2) selection of only epochs showing phase consistency.

Results

Optic disc diameter, logMAR, VEP amplitudes, and VEP SNR were all significantly inter-correlated. Optic disc diameter correlated best with VEP SNR (Spearman rho = 0.82; p < 0.001). Age-corrected logMAR correlated with optic disc diameter and VEP SNR (Spearman rho = ?0.695 and 0.70, respectively; p < 0.001). VEP latency poorly correlated with optic disc diameter or logMAR. Correction of phase shifts or selection of epochs based on phase consistency significantly increased VEP amplitude and SNR for children with optic disc diameters <1000 microns. Correction of phase inconsistency did not improve the correlation of VEP parameters with optic disc diameter or with logMAR.

Conclusions

In ONH, the size of the optic nerve is correlated with VEP SNR and logMAR. The results imply a direct relationship between the reduction in optic nerve axons and generalized reduction in visual function. Our calculation of VEP SNR provides objective assessment of optic nerve function that is independent of subjective scoring of VEP peaks.

     

Improving the function of the visual system in children with aphakia

Systematic reeducation by pleoptic-orthoptic exercises was performed in children with posttraumatic and congenital aphakia for the improvement of the visual acuity, normal retinal fixation and binocular vision. The treatment comprised 244 children aged 1-16 years who were formerly given a correcting contact lens on the aphakic eye. In the result of rehabilitation a visual acuity of over 5/16 was attained in 79.5 per cent of cases, a normal retinal fixation in 73.77 per cent and the binocular vision in 46.31 p.c. Better results were obtained after treatment of a posttraumatic cataract, poorer results after extraction of a congenital cataract.     

Stereopsis and binocular vision after surgery for unilateral infantile cataract.

PURPOSE: To assess the prevalence and level of binocular function in children with unilateral congenital or very early infantile cataract. METHODS: We retrospectively reviewed the charts of all patients with unilateral congenital or very early infantile cataract who underwent operation before 4 months of age, at the W. K. Kellogg Eye Center/University of Michigan Hospitals, from 1985 to 1995. Amblyopia was treated with a reduced patching schedule consisting of 1 hour per day per month of age for the first 6 months of life, in an attempt to improve binocular function by allowing more hours of binocular interaction during the presumed critical period for development of binocular cortical pathways. RESULTS: Thirteen patients met the inclusion criteria. Seven patients had persistent hyperplastic primary vitreous (PHPV) cataract and 6 had non-PHPV cataract. Overall, visual acuity of 20/80 or better developed in 69% of patients; 100% of eyes with non-PHPV cataract achieved visual acuity of 20/60 or better. Stereopsis of 400 arc seconds or better was detectable in 62% of patients, including 3 with PHPV cataract and 3 who required strabismus surgery in the first year of life. Three children had better than 150 arc seconds of stereopsis. The incidence of large-angle strabismus was 54%. CONCLUSIONS: Binocular cooperation, including gross and fine stereopsis, can develop in children with unilateral aphakia as a result of early removal of infantile cataracts. A less-strenuous patching schedule than has been historically advocated may foster this process, while restoring and maintaining good central visual acuity in patients with excellent compliance with contact lens and occlusion regimens.     

Visual results in children treated for macular retinoblastoma

PURPOSE: To evaluate the results of patching treatment in children with macular retinoblastoma in one eye. METHODS: Fifteen children affected by macular retinoblastoma received instructions for patching treatment for amblyopia. Data were collected on age at diagnosis of the tumor, presence of unilateral or bilateral disease, area of posterior pole involvement by the scar of the regressed tumor and its relationship to the fovea; and the onset, duration, and compliance of patching. The visual acuities recorded were expressed in logMAR (logarithm minimum angle of resolution) equivalents. RESULTS: Twelve children (80%) had bilateral retinoblastoma with the macular involved in one eye and three children had unilateral macular tumors. The median age at which patching was initiated was 15 months (range 4-36). Compliance to patching was good in 80% of children, with a median duration of 4 h (range 0.5-8) per day, 7 days per week, with total occlusion of the better eye. The median percentage of posterior pole involvement was 34% (range 11-100%). Eighty percent of children had some improvement in their visual acuity, and of the children in whom final logMAR acuity was recorded, 73% had an acuity of 1.0 logMAR or better and 53% an acuity of 0.5 logMAR or better after patching. There was no evidence of association between age of patient, sex, duration of patching, or percentage of posterior pole involvement and the improvement in visual acuity. CONCLUSIONS: In spite of the macular involvement of eyes with retinoblastoma, some visual recovery was achieved in 80% of children. Hence a trial of patching therapy is recommended for all children with involvement of the macula by retinoblastoma.     

Visual results after primary intraocular lens implantation or contact lens correction for aphakia in the first year of age

PURPOSE: The optimal role of intraocular lenses (IOLs) in infants remains a controversial topic. Some ophthalmologists advocate correction with a contact lens (CL), whereas others recommend an IOL correction. Our study compared visual acuity, ocular alignment, retreatment rate and binocular vision outcomes in children treated with these two methods at our clinic. METHODS: This study included 41 children with unilateral congenital cataract who underwent cataract surgery with posterior capsulorhexis and anterior vitrectomy, coupled with (IOL group, n=18) or without (CL group, n=23) primary IOL implantation. All infants underwent the first surgery during the first 12 months of their life and they were operated on in the period from 1994 to 1999. The mean age at surgery was 3.11+/-2.65 months (range: 28 days to 11 months). All patients were prescribed the same half-time reduced occlusion therapy. Good cooperation of the parents and good compliance with patching were the necessary conditions to include a patient in the study. Between January and February 2003, the final visual acuity and binocular vision outcomes were examined. RESULTS: The mean final visual acuity (logarithm of the minimum angle of resolution) of the operated eye was 0.43+/-0.33 for the IOL group and 0.58+/-0.39 for the CL group (p=0.14). The mean interocular difference in visual acuity was 0.22+/-0.29 for the IOL group and 0.56+/-0.31 for the CL group (p=0.042). The reoperation rate was 78% in the IOL group compared with 35% in the CL group (p=0.017). Esotropia or exotropia of more than 8 prism diopters were present in 55% of children (10/18) in the IOL group compared with 83% of children (19/23) in the CL group (p=0.039). CONCLUSIONS: We suggest that correction of aphakia after unilateral congenital cataract surgery with primary IOL implantation results in improved visual acuity, improved binocular vision outcome and less occurrence of strabismus, but a higher rate of complications requiring reoperation. Further studies with a larger pediatric patient group are necessary to confirm the optimal treatment of aphakia after unilateral congenital cataract extraction.     

Is the motion system relatively spared in amblyopia? Evidence from cortical evoked responses

Visual evoked potentials (VEPs) produced by pattern reversal were compared with those elicited by onset of motion in 37 amblyopic children (20 with anisometropic amblyopia, seven with strabismic amblyopia and 10 with both anisometropia and strabismus). The amplitudes and peak latencies of the main P₁ peak in the pattern-reversal VEP and of the motion-specific N₂ peak in the motion-onset VEP through the amblyopic eye were compared with those through the normal fellow eye. Regardless of the type of amblyopia, the amplitude of the pattern-reversal VEP for full-field stimulation was significantly smaller and its latency significantly longer through the amblyopic eye (P < 0.001). In contrast, neither the amplitudes nor the latencies of the N₂ motion-onset VEPs differed significantly between amblyopic and non-amblyopic eyes. For pattern-reversal VEPs through the amblyopic eyes, the extent to which amplitude was reduced and latency prolonged correlated well with the reduction of visual acuity, whereas the amplitudes and latencies of motion-onset VEPs did not vary with visual acuity. Even for stimuli restricted to the central visual field (5 or 2 deg diameter) or to the peripheral field (excluding the central 5 deg), motion-onset responses were indistinguishable through the two eyes, while pattern-reversal responses always differed significantly in amplitude. These results suggest that the source of motion-onset VEPs (probably an extrastriate motion-sensitive area) is less affected in amblyopia than that of pattern-reversal VEPs (probably the striate cortex). The motion pathway, presumably deriving mainly from the magnocellular layers of the lateral geniculate nucleus, may be relatively spared in amblyopia.