Glaucomatous optic neuropathy causes sensitivity loss to light offsets in the visual field.

The functional integrity of the 'on' and 'off' neurovisual pathways has been examined in the central visual fields of normal (n = 13), glaucomatous (n = 21) and ocular hypertensive (n = 21) individuals. The detection thresholds to light increments (onsets = bright spots) and light decrements (offsets = dark spots) on a uniform background were determined in each eye and the visual field scores were calculated for each of the subjects. Light offsets detected the presence of glaucomatous visual loss and also revealed significant early visual deficits which were missed by the conventional light onset stimuli. This study indicates that 'off-pathway' evaluation with light offsets can be used for the assessment of the functional integrity of the visual system and may reveal sub-clinical early glaucomatous optic neuropathy.