Motion-onset visual evoked potentials improve the diagnosis of glaucoma

Chronic glaucoma has been shown preferentially to damage larger retinal cells and optic nerve fibres that provide the input to the magnocellular visual pathway. We compared the motion-onset visual evoked potentials (primarily the magnocellular system) with those to standard pattern reversal in 20 patients with bilateral chronic glaucoma. For motion-onset visual evoked potentials, the pattern (isolated 40' checks of 10% contrast) moved in four cardinal directions (varied randomly from trial to trial) at a velocity of 10 deg/s for 20 ms, with an interstimulus interval of 1 s. In pattern-reversal stimulation, the checkerboard reversed at a rate of 2 reversals per second. In 60% of the eyes investigated, the results of both types of visual evoked potentials correlated, showing either normal (27.5%) or increased (32.5%) latencies. In the remaining 40% of the eyes, the normal pattern-reversal visual evoked potential latencies were accompanied by prolonged motion-onset visual evoked potentials. The high occurrence of delayed motion-onset visual evoked potentials in our patients confirms the primary magnocellular loss in chronic glaucoma and suggests that the motion-onset VEPs are suitable for detection of glaucomatous changes.