Figure 9. Representative records of gaze instability in two patients with bilateral visual loss.

(A) Gaze instability shown by P7, who had been blind since birth. Conventions are similar to Figure 2. The records show continuous eye drifts and nystagmus that changes direction, implying a “wandering null” or variable set point of the gaze-holding mechanism. (B) Gaze instability shown by P8, who had lost vision binocularly 3 years previously due to methanol poisoning. Horizontal gaze is disrupted by bidirectional drifts and saccadic intrusions; vertical gaze is disrupted by downbeat nystagmus. Double asterisks indicate SD values significantly different (p<0.01) from control subjects.