The past two decades have seen an increase in interest and
activity in vision screening of preschool children, an effort
directed toward the detection of treatable eye defects,
especially amblyopia. Articles written for the lay public have
recently been challenged for accepting a falsely high incidence
of amblyopia, and the value of early detection of amblyopia has
been questioned.1 Variations in the reported incidence of
amblyopia are traceable to many factors, including the sample
screened, the test used in screening, and the criterion adopted
for the definition of amblyopia. Studies of military and clinic
populations project a falsely high indication of the incidence
of amblyopia at most levels of its definition.2 Studies with
isolated letters or characters minimize the difference in acuity
between an individual's two eyes in comparison with the same
letters or characters arranged in lines on a chart. Small
differences detected by single targets are,