VERNIER ACUITY IN AMBLYOPIC AND NONAMBLYOPIC CHILDREN

We measured vernier acuity in normal and amblyopic children using a pr ocedure that resembles a video game and is suitable for testing most c hildren older than 4 years old. In this procedure, subjects align bars using two keys of a computer keypad. Following binocular practice tri als, monocular vernier acuity was measured in 38 control children, 5 t o 15 years old, and in 18 children with histories of amblyopia. Vernie r acuity was defined as the standard deviation of adjusted position ac ross a block of six trials. Vernier acuity improved as a function of a ge in the control subjects, indicating developmental improvement. Ambl yopic subjects with strabismus (n=5) and with both anisometropia and s trabismus (n=8) showed markedly impaired vernier acuity in their ambly opic eyes, with vernier acuitys four to five times larger than those o f age-matched controls. However, the amblyopic subjects who were aniso metropic (n=5), without any history of strabismus, were not significan tly different from control subjects in either eye. Testing with bars a nd gratings gave similar results. To our knowledge, this is the first study showing that vernier acuity deficits seen in adult amblyopes are also seen in child amblyopes.