Peripheral contrast sensitivity for dynamic sinusoidal gratings in early glaucoma

Automated contrast thresholds were established for dynamic, 2 reversals per sec phase-shifted, sinusoidal gratings in a 5 degrees circular test field centred 7.5 degrees from the fixation point in six positions in the visual field in 16 patients (age 56-76 years) with clinically established (optic disc or nerve fibre layer damage) early glaucoma, without visual field defects. For reference, contrast thresholds were also obtained in 16 sex-matched and age-matched controls. For all three spatial frequencies, thresholds were raised in the glaucoma group (0.5 c/deg: p = 0.0034-0.041, 2 positions n.s.; 1.0 c/deg: p = 0.0093-0.049, 1 position n.s.; 2.0 c/deg: p = 0.0011-0.041, 1 position n.s.). Deficiencies did not correlate to glaucoma type (simplex vs capsular), intraocular pressure level at examination, visual acuity, or local therapy (beta-blockers vs miotics). In the glaucoma group, there was a general loss of contrast sensitivity in all six positions tested in the visual field, reflected in roughly similar threshold elevations. Losses appeared slightly greater in the lower hemi-field. Definite contrast threshold elevations from the early glaucomatous process were established in this group of glaucoma patients without visual field defects. However, the method was considered to be of less value in glaucoma detection for individual subjects, due to the large overlap in threshold values between glaucoma patients and controls.