Saccadic eye movement dysfunction in Alzheimer's disease

Saccades were measured by magnetic search coil technique in 13 patients with Alzheimer's disease and compared with those of 11 age-matched control subjects. We analyzed responses to target motion of predictable and unpredictable timing or amplitude, and responses to briefly flashed targets. Latencies were significantly prolonged and peak velocities reduced only when the timing of target motion was unpredictable. Saccades to predictable amplitude targets were abnormally hypometric. In 8 patients, impersistence of gaze was manifested by large-amplitude saccadic intrusions away from the intended position of gaze. When instructed to make saccades away from a flashed target, patients made reflexive saccades toward the target. We attribute this visual grasp reflex to frontal lobe degeneration. These eye movement deficits can be used to quantify motor dysfunction in Alzheimer's disease.