Analysis Of Changes In The Cortical Responses Of An Amelyopic Patient Pre-Vision Therapy Versus Post-Visiion Therapy.

Pattern reversal visual evoked responses (PVER) are an objective way to measure cortical responses in a patient, to measure visual acuity, and to diagnose certain ocular conditions. Amblyopia, clinically defined as a decrease in best corrected visual acuity to less than 20/30 in one eye or a two line difference between the two eyes with no apparent pathological cause, is easily diagnosed by PVER. Amblyopic PVER's show decreased amplitudes and increased latencies compared to the normal eye. The amblyopic eye also shows a peak PVER response to a stimulus check size of 30 to 40 minutes of arc, as compared to the peak response of the normal eye to stimulus check sizes of 10 to 20 minutes of arc. Although these characteristic PVER responses have been demonstrated by many researchers, minimal attention has been paid to the effects of visual training on the PVER response. In this study, a 12 year old anisometropic-strabismic amblyope with visual acuities of 20/20 in the right eye and 20/40 in the left eye was recruited as a patient. Pre-visual training PVER's were performed on the patient. A sequential visual training program was initiated including full refractive correction, direct occlusion, and active visual training to remediate the amblyopia and strabismus. PVER's were monitored every one to two months during visual training. A final PVER was recorded two months after the cessation of visual training. The results of this single patient study suggest that there is limited value
in monitoring PVER's during amblyopia treatment as an index of visual training
success because the responses obtained were too variable to draw conclusions from.
Although the results of this study were contaminated by the patient dropping out
of visual training prior to establishing a full functional cure, the data does
suggest some differences in the PVER's measured pre and post visual training.
Further investigation on a larger clinical population who will follow the visual
training program to its completion, is warranted to see exactly how much change
in cortical function is occurring as a result of visual training for amblyopia.