Decreased contrast sensitivity in normal tension glaucoma determined by pattern visually evoked cortical potentials.

Little is known about the central visual function of patients with normal tension glaucoma (NTG). We estimated the contrast sensitivity of patients with NTG and normal subjects with the use of pattern visually evoked cortical potentials (PVECPs). PVECPs were recorded using checkerboard pattern reversal system display on television monitor of check size 15', 60' and frequency 3 reversals per second and contrast varied in 7 steps. Our results show that a significant delay of the P100 component for 60' check size in the NTG group was found at every contrast level (P < 0.05). Contrast threshold was determined as the value to obtain a criterion peak latency from a regression line calculated within a contrast range from 10% to 56%. The contrast threshold for both check sizes of the NTG group showed an increased threshold (P < 0.05). We conclude that contrast sensitivity decreased in NTG as determined by PVECP. The PVECP was a sensitive test for detecting the functional abnormalities of NTG.