Low-luminance contrast stimulation is optimal for early detection of glaucoma using multifocal visual evoked potentials

Purpose. The blue-on-yellow multifocal visual evoked potential (BonY mfVEP) stimulus is more sensitive than the conventional black-and-white pattern-reversal stimulus in identifying early glaucoma. BonY employs pattern-onset stimulation and lower luminance contrast (40%) in addition to color. This study was conducted to elucidate the mechanism responsible for the enhanced performance of the BonY stimulus. Methods. Multifocal pattern-onset VEPs were recorded in response to BonY, high-luminance contrast achromatic (HLA) and low-luminance contrast achromatic (LLA) stimulations in 30 normal subjects (to construct normative databases) and 23 patients with early glaucoma (mean deviation [MD] < 6 dB). In addition, the specificity of BonY and LLA stimulation was examined in a subset of 25 normal subjects. Results. In normal subjects, LLA mfVEPs had significantly lower amplitudes than did BonY and HLA mfVEPs (P < 0.001), which were not significantly different from each other. In glaucomatous eyes, all three stimuli demonstrated significantly reduced amplitudes in comparison with those of normal eyes. Although the sensitivities of both BonY and LLA in identifying subjective visual field defects were similarly high (93% and 89.7%, respectively), HLA showed only a 79.3% detection rate. BonY and LLA demonstrated significantly higher defect severity scores than did HLA (P < 0.05 for both). Specificities for BonY and LLA were similar (96%). Conclusions. BonY and LLA mfVEPs performed comparably, and both were significantly better than the HLA mfVEP in identifying early glaucoma. Enhanced performance of BonY stimulation is most likely due to its low-luminance contrast component rather than the pattern-onset mode of presentation or its chromatic properties.