Target predictability influences the distribution of coordinated eye-head gaze saccades in patients with homonymous hemianopia.

In hemianopic patients target predictability plays a differential role for the distribution of different types of initial saccades. A linear correlation was shown to exist between the adaptive state of reading capability and the probability of a correct initial eye-head gaze saccade that hit the target accurately. A constant target frequency of 0.8 Hz was found to be the optimum frequency for hemianopic patients to follow square step targets with an eccentricity of +/- 20 degrees. Variability of the compensatory eye movement velocity gain was lowest at this frequency. We were able to use this target frequency as a test for a clinical classification of the status of adaptation of hemianopic patients in combination with simple reading tests. The repetition of this manoeuvre could correct the synkinesis and the balance of the VOR during active gaze of hemianopic patients.