Identification of Preferred Retinal Loci during Binocular Viewing in Patients with Central Vision Loss

Abstract

Purpose: Until now, the absolute location of the PRL of patients with central vision loss could only be identified monocularly. We tested a new method to measure/predict the location of the PRL in each eye in patients with central vision loss when viewing binocularly. The method uses a unique remote eye-tracking system that estimates the optical axes of both eyes without user calibration. We hypothesized that this method predicts the locations of monocular and binocular PRLs accurately.

Methods: Five experienced controls and 6 patients with stable central vision loss were tested. Their fixation was recorded monocularly with both the MP-1 microperimeter and the eye-tracking system and binocularly with the eye-tracking system. The eye-tracker measured the direction of the optical axis and the angle between the PRL (fovea for control subjects) and the optical axis in each eye. The MP-1 measured the location of the PRL relative to the optic disk; that is, its absolute location. Using the monocular measurements of the eye-tracker and the MP-1, in control subjects, a transformation from eye-tracking measurements to MP-1 measurements was created and used to predict the absolute location of the PRLs in patients. The predicted values for monocular viewing for each eye were compared with the measured MP-1 values.

Results: The prediction errors of the horizontal and vertical coordinates were -0.1 ± 0.7 deg and -0.1 ± 1.1 deg for the right eye, and -0.1 ± 0.9 deg and 0.0 ± 1.0 deg for the left eye. The same transformation was then used with measurements of the eye-tracker’s PRLs under binocular viewing, to obtain the absolute locations of the PRLs in the MP-1 coordinate system.

Conclusions: By transforming the measurements of the PRL location from an eye tracking coordinate system to the MP-1 coordinate system, the absolute location of the PRLs (i.e., relative to the optic disk) during binocular viewing can be predicted with an acceptable accuracy.

Keywords: 412 age-related macular degeneration • 584 low vision • 524 eye movements: recording techniques