Selective simulation of non-redundant pathways enhances in detection of glaucoma using multifocal VEP

Abstract

Purpose: In a recent study, we demonstrated superior performance of Blue-on-Yellow pattern-onset multifocal VEP in identifying glaucomatous visual field defects as compared to black and white pattern-reversing checkerboard stimulation. We hypothesized that Blue-on-Yellow stimulation specifically targets non-redundant koniocellular visual pathways, enhancing identification of early losses. Current study was aimed at investigating comparative sensitivity of various pathways using temporally similar (pattern-onset) stimulus presentation technique. Methods: 23 patients with early perimetrically proven glaucoma (MD < 6 dB, repeatable defects) underwent mfVEP using three different pattern-onset stimulation conditions: high (98%) luminance contrast achromatic (HC), low (50%) luminance contrast achromatic (LC) and Blue-on-Yellow (BonY) stimulation to preferentially stimulate parvocellular, magmocellular and koniocellular pathways respectively. The order of tests was randomized. Normal database (30 healthy subjects) was constructed for each test condition. Results: The HVF identified scotomas in 28 eyes of the 23 patients. 21 of the scotomas were identified by HC mfVEP (75%), 26 were identified by BonY (93%) and all 28 (100%) by LC mfVEP. Comparison of defect severity using Accumap Severity Index (ASI) demonstrated largest averaged value for LC (62.7 + 28.5), followed by BonY (56.5 + 28.8) with HC showing less abnormality (41.5 + 31.5). ANOVA revealed significant differences between the groups, with LC and BonY ASI values significantly larger than HC (p<0.001 and p<0.01 respectively), but no significant difference between LC and BonY (p=0.16). Conclusions: Both BonY and LC achromatic mfVEP performed significantly better than HC pattern-onset stimulation in identifying early glaucomatous defects. Enhanced performance of BonY and LC may be attributed to non-redundancy of the koniocellular and magnocellular pathways.1 page(s