No abstract

We compared stereoscopic thresholds determined psychophysically and by using visually evoked potentials in normal adult and stereoblind subjects. For normal observers there was a strong linear relationship between visual evoked potential amplitude and disparity (r = 0.86 on average). However, stereoblind observers' responses showed no relationship to disparity (r = 0.18 on average). For normal observers, log visual evoked potential stereo thresholds determined by an extrapolation procedure were on average within 0.17 octaves of the psychophysically determined log thresholds. They did not differ significantly from psychophysical thresholds, and they correlated significantly with behavioral thresholds (r = 0.86).

Cataract patients suspected of having disease that might interfere with good postoperative visual function were evaluated by eliciting monocular steadystate luminance visual evoked potentials (VEPs) with closed eyes at a stimulus rate of 10 flashes/sec. VEPs were rated as either normal or abnormal. Patients with normal VEPs were predicted to have visual acuity of 6/15 (20/50) or better. Patients with abnormal VEPs were predicted to have acuities of 6/18 (20/60) or worse. Postoperative acuities were determined for all patients who underwent surgery and who had no intraoperative or early postoperative complications. The predicted and observed postoperative acuities were quantitatively compared for the 59 patients who met these criteria, using a 2 × 2 contingency table. The chisquare was significant (p<.001). The overall accuracy of prediction was 80%. Accuracy of the predictions for patients with preoperative acuities of 6/60 (20/200) or better was compared with the accuracy of the predictions for those with preoperative acuities of 60/120 (20/400) or worse. There was no significant difference (p>0.10).