Depth of strabismic amblyopia determined with neutral density filters

We used a neutral density filter to assess motor responses in the fixation patterns of 25 patients, ranging in age from 5 to 54 years, with strabismic amblyopia. Shifts of fixation back to the preferred eye occurred when the visual acuity of the preferred eye through the filter was marginally better than that of the amblyopic eye. Thus, we were able to correlate the level of the filter at which this shift occurred with the level of amblyopia. This technique may be particularly helpful in the examination of preliterate children and in monitoring the progress in the treatment of amblyopia.