The critical period for surgical treatment of dense congenital bilateral cataracts

Abstract

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.

Figure 1

Four models of the effects of bilateral deprivation on longterm logMAR recognition acuity outcome: A. age at surgery has no effect on longterm visual acuity outcome, B. the earlier the surgery the better the longterm visual acuity outcome, C. there is an early window of time, beginning at birth, during which an optimal outcome can be attained but, if surgery is delayed beyond this window, longterm visual acuity outcome declines progressively, D. delay in surgery is associated with progressive decline in visual acuity outcome only during the first weeks of life, after which there is no further effect of duration.

Figure 2

Longterm visual acuity outcome for 37 patients (74 eyes) treated for dense congenital bilateral cataracts along with the best-fit bilinear model of the critical period (solid line). Associated adverse outcomes are indicated by symbol type.