THE CRITICAL PERIOD FOR SURGICAL-TREATMENT OF DENSE CONGENITAL UNILATERAL CATARACT

Purpose. Early treatment of dense congenital unilateral cataract is as sociated with better acuity outcomes. it is unclear whether there is a gradual worsening of prognosis with delay of treatment from the time of birth (linear model) or whether there exists an early window of tim e during which treatment is maximally effective, followed by declining success (bilinear model), Tile aim of the current study was to determ ine which model better describes the response to treatment. Methods. A maximum likelihood procedure that permits statistical comparison betw een linear and bilinear models was applied to acuity outcomes from a g roup of 45 children 5 to 8 years of age with a history of dense congen ital unilateral cataract diagnosed at 1 to 10 days of age. Contrast se nsitivity and vernier acuity data from a subset of these children were evaluated with nonparametric statistical methods. Results. The biline ar model provided a significantly better fit to the acuity outcome dat a. The Line fitted to tile initial portion of the function had a shall ow slope that was not significantly different from 0.0, The intersecti on of the two Linear functions occurred at 5.6 weeks and was followed by a steep decline in visual acuity outcomes, Contrast sensitivity and vernier outcome measures over a range of spatiotemporal conditions sh owed better outcomes were obtained with early treatment. Conclusions. Intervention before 6 weeks of age may minimize the effects of congeni tal unilateral deprivation on tile developing visual system and provid e for optimal rehabilitation of visual acuity.