The effect of minimal occlusion therapy on binocular visual functions in amblyopia

The binocular visual functions of amblyopic children were studied during treatment involving brief weekly periods of occlusion of the unaffected eye while the child performed demanding visuomotor tasks against either a background of rotating gratings or a stationary uniform gray stimulus. The gains in stereoacuity were quite significant and in most cases more obvious than the rather small gains in letter visual acuity. On initial presentation only 21 of the 60 patients showed evidence of stereopsis and of these only seven possessed a stereoacuity of 100 secs or better. Following six treatment sessions the number of patients that demonstrated stereopsis increased to 36 of whom 17 possessed reasonably good stereoacuity (100 secs or better). However, there was no difference in the degree of improvement exhibited by those patients that viewed rotating grating patterns during treatment and others from the control group that viewed the uniform gray stimulus. Thus, there was no evidence that any of the visual gains were enhanced or promoted by active visual stimulation of the amblyopic eye with rotating gratings during the brief periods of occlusion of the unaffected eye. Finally, a comparison of the scores of the children on various stereo-tests suggest that tests comprised of small figure elements that are present in high density may be best for screening purposes. On the other hand, for quantifying the stereoacuity of children known to possess abnormal binocular vision it may be more appropriate to employ tests that use large figure elements that provide strong fusion cues.