Introduction: We examined the critical period for deprivation amblyopia in a cohort of patients with dense bilateral congenital cataracts to investigate the optimum timing for surgical treatment.
Methods: Thirty-seven infants with dense bilateral congenital cataracts that were extracted by 31 weeks of age were enrolled prospectively. Visual acuity outcome was assessed at >/=5 years of age. We statistically evaluated which of 4 models provided the best fit to the data: (1) no change in visual acuity outcome with delay in surgery, (2) linear decline of outcome with delay, (3) a bilinear model in which a critical age exists after which outcome depends on delay, and (4) a bilinear model in which a critical age exists before which outcome depends on delay. In addition, we reviewed medical records for associated adverse outcomes, including strabismus, nystagmus, secondary membrane formation, and glaucoma.
Results: A bilinear model with a critical age of 14 weeks fit the data better than a linear model (chi(2) = 14.7; p < 0.0006). During weeks 0-14, mean visual acuity decreased by 1 line with each 3 weeks' delay in surgery. From 14 to 31 weeks, visual acuity was independent the subject's age at surgery, averaging 20/80. Surgery after 4 weeks was associated with a greater prevalence of strabismus and nystagmus than surgery before 4 weeks, whereas surgery during the first 4 weeks was associated with a greater prevalence of secondary membrane formation and glaucoma.
Conclusions: We did not find a latent period for the treatment of children with dense bilateral congenital cataracts. Deprivation amblyopia may be minimized with early surgery for bilateral cataracts.