Abstract
Purpose: :
In previous work we have shown the deficits caused by strabismus onset at birth in infant monkeys (Wong et al, 2003). Here we report our findings when strabismus onset is delayed until age 3 weeks.
Methods: :
Eight infant macaques were fitted with prism goggles at three weeks of age to induce large magnitude optical strabismus. The goggles were removed, emulating surgical repair of strabismus in humans, after 3 wks (n=2), 6 wks (n=2), 9 wks (n=2) or 12 wks (n=2). At age 1 year the monkeys were trained to perform visual fixation and tracking tasks and eye movements were recorded using the scleral search coil technique.
Results: :
The shortest-duration monkeys (3 wks) regained normal eye alignment, exhibited stable fixation and symmetric pursuit/OKN. In contrast, the intermediate and long-duration monkeys (6, 9 and 12 wks) exhibited persistent heterotropias, pursuit/OKN asymmetries and latent nystagmus. The severity of these ocular motor deficits increased with increasing duration.
Conclusions: :
Infant monkeys with later-onset strabismus have deficits comparable to that of birth-onset strabismic monkeys. The absence of these signs in the shorter-duration monkeys reported here implies that shorter periods of duration can produce good repair of the cerebral ocular motor circuits.
Keywords: strabismus • eye movements • nystagmus