The effect of blinks on the accuracy and velocity of saccades - A study based on the scleral search coil technique

Large saccadic gaze shifts are frequently accompanied by blinking. Using th e magnetic search coil technique, we investigated the effect of voluntary b links on the eye position during fixation and on saccades of five normal su bjects and three patients suffering from Niemann-Pick type C disease. Blink s during fixation reproducibly caused downward and nasalward deflections of both eyes. Each participant had to perform 20 and 40 degree vertical or ho rizontal saccades between two continuously visible targets: at first withou t blinking and then with a blink together with each saccade. The saccadic a ccuracy was not affected by blinks in the normal subjects. However, blinks caused considerable changes in the dynamic properties of saccades: for 20 d eg saccades the peak velocity was markedly decreased in all subjects (avera ge 19%) as compared with saccades without blinks. On the other hand, the du ration of saccades with blinks was increased by an average of 36 %. The eff ects of blinks on 40 deg saccades were similar, but the changes were somewh at smaller. In contrast to normal subjects, patients with Niemann-Pick dise ase were able to increase and speed up their hypometric and slow vertical s accades by blinking.