OBJECTIVE To study the development of grating acuity in children treated for dense congenital unilateral or bilateral cataract and to examine how variations in treatment affect grating acuity during early childhood. METHODS The authors used optokinetic nystagmus (OKN), preferential looking (PL), or both to measure the grating acuity of children treated for congenital cataract in one eye (n = 63) or both eyes (n = 77) whenever possible from the time of treatment until 3 years of age. At each age, the authors compared patients' monocular acuity to that of children with no history of eye disorders. RESULTS The OKN acuity of treated eyes did not improve with age and was abnormal by 12 months of age. In contrast, PL acuity improved with age, and acuity of most treated eyes was not outside normal limits until 24 to 30 months of age. Nonetheless, at 12 months and at 3 years of age, PL acuity correlated significantly with age at treatment in children who had bilateral cataract. In children who had unilateral cataract, PL acuity correlated significantly with the number of hours per day the good eye had been patched since treatment. Children whose good eye was patched fewer than 3 hours per day did significantly worse than children treated at a comparable age for bilateral congenital cataract. However, children whose good eye was patched at least 3 hours per day had PL acuities similar to those of children treated at a comparable age for bilateral congenital cataract. CONCLUSIONS Children treated for congenital cataract show deficits in grating acuity, with the deficit apparent earlier in OKN acuity than in PL acuity. At least by 1 year of age, visual development has begun to be influenced by the age at treatment and, in children treated for unilateral cataract, by patching of the good eye.