Predicting potential acuities in amblyopes : Predicting post-therapy acuity in amblyopes

Amblyopic patients, or their parents, often want to know the potential for success before committing to treatment. Recent reports have indicated that the pattern visual evoked potential (pVEP) can be used as a predictor of the success of amblyopia therapy. Unfortunately, these studies did not determine if acuity estimates from pVEPs could accurately predict the acuity post-treatment. Furthermore, pVEPs are not always practical to obtain because of the time necessary to acquire the data. Sweep VEPs (sVEP) offer the advantage of rapidly estimating visual acuity in amblyopic patients. In this retrospective study, the relationship between sVEP acuities measured pre-amblyopic therapy and Snellen acuities measured post-amblyopic therapy was determined. Seventeen patients with amblyopia were studied. Monocular sVEP and Snellen acuities were determined pre-amblyopic therapy and Snellen acuities were determined post-amblyopic therapy. An Enfant 4010 computer system was used to produce the stimuli, record the VEPs, and extrapolate the acuity. The stimuli were horizontally oriented, sine wave gratings (11 spatial frequencies from 2 to 24 cpd) with a contrast of 80%, counterphased at 7.5 Hz. Standard VEP recording techniques were employed. Therapy consisted of the full refractive correction and occlusion combined with active vision therapy. The patients demonstrated a significant improvement in pre- to post-amblyopic therapy Snellen acuities (P < 0.00001). The intraclass correlation coefficient (r (i)) between the pre-therapy sVEP acuities and the post-therapy Snellen acuities was 0.73. A paired t-test did not find a significant difference between the two sets of data (P = 0.94). For the amblyopes in this study, the average difference (+/-SD) in the sVEP acuity estimate and the final Snellen visual acuity was +0.002 +/- 0.123 logMAR acuity lines. The results indicate that pre-amblyopic therapy sVEP acuity can be a good predictor of post-amblyopic therapy Snellen acuity.