Eye Movements Patterns in Walking Hemianopic Patients

Abstract

Abstract: : Purpose:To measure and analyze the pattern of eye movements of patients with homonymous hemianopia while walking for an extended period. This information should help in the design of mobility visual aids for these patients. Methods:We measured the eye position of people while they walked in unfamiliar environments. Three homonymous heminanopia patients (CH1 and CH2 complete, and IH3 with partial recovery of 20°×10° in the lower hemianopic field) were tested indoors and outdoors (city street) and were compared with three normally sighted observers. A head mounted eye-tracking device (I-SCAN) was used to recorded eye position with reference to the head. Spatial histograms of eye angular position were calculated. Kinetic perimetry and fixation stability during static perimetry were measured in patients with a Scanning Laser Ophthalmoscope (SLO). Results:Patients presented different fixation pattern while walking. Patient CH1 showed a horizontal asymmetric pattern of ocular movements while walking, with many more fixations towards the seeing side. This subject demonstrated steady fixation in the SLO. The other two patients presented a more symmetric horizontal pattern of eye movements while walking. These two subjects showed dynamic horizontal scanning displacements of the point of regard when they were asked to fixate in the SLO. Conclusion:Patients with complete hemianopia can partially compensate by performing a dynamic eye scanning and thus show a symmetric scanning. Dynamic gaze scan towards the scotoma brings more spatial field of interest into the visible part of the retina. Partial field recovery may be sufficient to regain the normal symmetry of ocular movement in incomplete hemianiopia. Field enhancement devices should allow for essentially normal eye scanning range in both sides.

Keywords: 459 low vision • 406 eye movements