Lack of alternation in patients treated for strabismic amblyopia.

Of a series of 57 formerly amblyopic patients who attained equal visual acuities (20/20 or better in each eye), only 29 were able to alternate after treatment. The oldest patient was 5 years old. The pattern visual-evoked response of the previously amblyopic eye in nonalternators showed a reduced amplitude as compared with that of the sound eye. This probably occurred because of a reduced number of cortical cells subserving the formerly amblyopic eye. Lack of alternation may be the result of cortical competition. More cortical cells are connected to the originally normal eye even after successful treatment of the amblyopic eye in the nonalternating patient.