A total of 19 children (mean age 8.7 years [SD 1.8]; range, 5.3–12.3 years of age) diagnosed with classic infantile ET
7,8 were referred for this study at the Retina Foundation of the Southwest by nine pediatric ophthalmologists. Age at diagnosis and duration of constant infantile ET were based on medical record review. From these records, we identified 10 children with a short duration of constant ET (≤3 months) and 9 children with a long duration of constant ET (≥5 months) before alignment. Duration of constant ET was defined as the number of months between the initial diagnosis of constant ET and the age of alignment. Age at alignment was defined as the age in months at which alignment within 0 to 6 prism diopters (PD) was first achieved and maintained for at least 12 months. Coupled with a short duration of ET, the 6 PD criterion is associated with the recovery of binocular function.
14–16 Both disparity sensitivity and disparity vergence develop rapidly during the first year of life, so later misalignments would be expected to have little effect on disparity vergence.
17,18 At the time of testing, all children had 0.2 logMAR (20/32) or better visual acuity in each eye and were aligned within 6 PD of orthotropia by simultaneous prism and cover test at near; misalignment that exceeds 6 PD precludes high grade stereoacuity.
1,19 In addition, 22 age-similar control children (mean age 8.5 years [SD 2.2]; range, 5.2–11.8 years of age) with healthy visual acuity, normal Randot stereoacuity, and no history of vision disorders were enrolled. All children wore their habitual optical correction during testing if applicable. Exclusion criteria were prematurity ≥8 weeks, coexisting ocular or systemic disease, congenital infections or malformations, and developmental delay.