Blue-yellow and standard pattern visual evoked potentials in phakic and pseudophakic glaucoma patients and controls

Blue-yellow short wavelength testing (BY-VEPs) has proven diagnostic relevance in detecting early ganglion cell damage, e.g., in glaucoma. To date testing has generally been conducted using individual protocols without consideration of the lens status. In this study, we compared changes in BY-VEPs and standard pattern VEPs in phakic and pseudophakic glaucoma patients and controls.

The eyes of 57 healthy controls (18 pseudophakic and 39 phakic) and 67 glaucoma patients (29 pseudophakic and 38 phakic) were included in a prospective study. Phakic eyes were arranged in three groups according to the Lens Opacities Classification System III. Transient on/off isoluminant blue-yellow 2° checks were used for BY-VEPs, transient large 1° (M1) and small 0.25° (M2) black-white checks for standard pattern reversal VEPs, according to the ISCEV standards.

Latencies and amplitudes of M1 and M2 did not differ significantly between groups or lens status. ANOVA analysis revealed significantly longer BY-VEP latencies in glaucoma compared to controls (p = 0.002), independently of the lens status. The amplitudes showed no such pattern (p = 0.93). Mean defect (MD) was significantly negatively correlated to BY-VEP latency (r = -0.54, p = 0.003) only in pseudophakic glaucoma patients. Different stages of cataract did not show a significant effect on the BY-VEP latencies.

Glaucoma led to a significant increase of BY-VEPs latencies, while standard pattern VEPs were not influenced. The correlation of MD and BY-VEP latency only in pseudophakic glaucoma patients indicates a substantial confounding effect of lens opacifications on the diagnostic value of BY-VEPs in glaucoma.