Alternate Fixation in the Non- Strabismic Child

A modification of the binocular fixation preference test is described using a 25A prism B.I., in a non-strabismic child. The induced esotropia is compared, using a fixation light, as the prism is alternately placed before each eye. Those children whose fixation alternates as the prism is alternated have equal vision. This test does not distinguish equal from unequal vision in those children whose fixation does not alternate.