Gaze changes with binocular versus monocular viewing in age-related macular degeneration

Abstract

Purpose: To determine and explain gaze changes during binocular versus monocular viewing in patients with age-related macular degeneration (AMD).

Design: Cross-sectional study.

Participants: Twenty-nine patients with bilateral late-stage AMD.

Methods: Distance acuity and fundus pathologic features were evaluated. Eye position was recorded while viewing a circular fixation target under monocular and binocular viewing conditions using an infrared eye tracker (SMI Gazetracker, SensoMotoric, Germany; Eyelink Software 2.04). Gaze changes were quantified by calculating the mean x-coordinate and y-coordinate eye position of the center of the bivariate contour ellipse area for a 30-second fixation task under both viewing conditions. Retinal loci used for monocular fixation for each eye were determined using the scanning laser ophthalmoscope (SLO; SLO 101, Rodenstock, Munich, Germany).

Main outcome measure: Gaze position.

Results: Nine patients showed no shift in gaze position from monocular to binocular viewing. Three patients demonstrated a shift in both eyes, and 17 patients demonstrated a shift in only 1 eye. The mean shift was 4.7+/-5 degrees (standard deviation). The shift in gaze position in the worse eye was predictive of the distance between the 2 monocular preferred retinal loci (PRLs; better and worse eye; r(2) = 0.59; P<0.0001), whereas there was no association between the shift in gaze position in the better eye and distance (r(2) = 0.00; P = 0.91).

Conclusions: Most AMD patients shift gaze position in 1 or both eyes when viewing binocularly compared with monocularly. These changes suggest that different retinal locations are used for fixation under the 2 viewing conditions. The SLO data showed that these patients are likely to demonstrate monocular PRLs that fall on noncorresponding areas. These results may have implications for the effective development of eccentric viewing and binocular behavior of AMD patients.