EARLY TREATMENT OF CONGENITAL UNILATERAL CATARACT MINIMIZES UNEQUAL COMPETITION

PURPOSE. Dense congenital unilateral cataracts may compromise visual d evelopment through visual deprivation and biased interocular competiti on, whereas dense congenital bilateral cataracts compromise visual dev elopment primarily through visual deprivation alone, Differences in se nsory deficits between the two patient groups with these disorders may reflect the specific effects of unequal competition. To determine whe ther early treatment (at <8 weeks of age) minimizes the adverse effect s of unequal competition grating acuity deficits during the immediate posttreatment period and contrast sensitivity deficits at 6 to 8 years of age were assessed in 29 children with. histories of dense congenit al unilateral or bilateral cataracts who had had treatment between 1 a nd 8 weeks or 12 and 30 weeks. All children maintained good to excelle nt compliance with optical correction and occlusion therapy. METHODS. Grating acuity was measured using a two-alternative forced-choice pref erential-looking staircase protocol. Contrast thresholds at three spat ial frequencies (0.38, 1.5, and 6 cyc/deg) were measured at each of tw o temporal frequencies (2- and 8-Hz sinusoidal counterphase modulation ) using DG grating patches. RESULTS. Grating acuity deficits in the im mediate posttreatment period were similar in patients with a history o f unilateral cataract (n = 10) and those with a history of bilateral c ataracts (n = 6) when treatment was provided during the first 8 weeks of life. With later treatment, patients with a history of unilateral c ataract (n = 7) had significantly larger grating acuity deficits than patients with a history of bilateral cataracts (n = 6). Children with a history of dense congenital unilateral cataract had similar deficits in contrast sensitivity to children with a history of bilateral catar acts when treatment was initiated during the first 8 weeks of life. Wh en treatment was initiated later (i.e., at 12-30 weeks), patients with a history of unilateral cataract showed greater deficits in contrast sensitivity and a dependence of the amount of spatial contrast sensiti vity deficit on temporal frequency than did patients with a history of bilateral cataracts. CONCLUSIONS. These findings support the hypothes is that only visual deprivation is active as an amblyogenic factor dur ing the first weeks of life, but when unilateral deprivation is prolon ged to 12 to 30 weeks, unequal competition also plays a role in amblyo genesis.