Diffuse Loss of Sensitivity in Early Glaucoma

Purpose: To establish whether there is significant diffuse loss of sensitivity in a population of patients with early glaucoma.

Methods: The differential light sensitivities at the 10 most sensitive locations from within the central 24 degrees of program 30-2 of the Humphrey Field Analyzer (Humphrey Instruments, San Leandro, CA) were compared in 38 pairs of age-matched subjects, one of each pair with early primary open-angle glaucoma (POAG) and the other with normal eyes. All subjects had had experience with automated perimetry and had clear media, visual acuity of 20/25 or better, and one or fewer false-positive or false-negative responses to catch trials.

Results: The mean difference in age between the subjects with glaucoma and normal subjects was 29 days (P = 0.44, maximum 1.42 years). The mean paired difference in pupil size was 0.16 mm (P = 0.26), and visual acuity was higher in the glaucoma-affected subjects (P = 0.044). The 10 highest sensitivity measurements in the POAG-affected subjects were found to be lower by a median of between 1.0 and 2.0 dB than those in the normal pair members (0.0001<P<0.012, sign test). In 60% of the pairs the sensitivity at the seventh most sensitive location was 2 dB or more lower in the POAG-affected eyes.

Conclusions: Early glaucomatous visual field loss frequently involves a diffuse component that includes the 10 most sensitive locations. These findings suggest that purely localized visual field loss in glaucoma is rare. These observations could not be explained by factors of pupil size and media opacity.