Abstract
Abstract: :
Purpose: Pursuit/OKN and gaze–holding remain maldeveloped in human infants who have strabismus that is not repaired within 3 mos of onset. The purpose of the study was to determine how short vs. long durations of strabismus influence the development of cortically–mediated eye tracking behaviors in primates. Methods: Infant macaques were fitted with goggles on day 1 of life. A Short Duration group (2 experimental and 1 control) wore the goggles for a period of 3 wks (the equivalent of 3 mos in humans). Long Duration groups (5 experimental and 1 control) wore the goggles for a period of 3 mos or 6 mos (the equivalent of 12–24 mos in humans). The experimental animals wore prism goggles to induce optical strabismus of 11.4 – 22.8 deg while the control animals wore goggles with plano lenses. At age 1–2 years, the monkeys were trained to perform visual fixation and tracking tasks, and eye movements were recorded using search coils. Results: Short Duration monkeys regained normal eye alignment and showed stable fixation. Horizontal smooth pursuit and large field OKN movements were symmetric under conditions of monocular viewing, with gains comparable to control monkeys. In contrast, Long Duration monkeys showed persistent heterotropias, pursuit/OKN asymmetry, latent nystagmus, and vertical deviations similar to those observed in strabismic humans. Conclusions: Shorter vs longer durations of strabismus in primates prevents the constellation of ocular motor defects that typify infantile esotropia.
Keywords: strabismus • eye movements • nystagmus