Comparison of Two Methods for Measuring Eccentric Fixation in Patients With Age–Related Macular Degeneration

Abstract

Abstract: : Purpose: We compared the patterns of eye fixations of people with age–related macular degeneration (AMD) and dense scotomas in two conditions that require eccentric fixation: 1) a single–optotype acuity task, and 2) static macular perimetry. Methods: Ten patients with AMD were tested in the two tasks using their better eye. During the acuity task, fixation location was monitored with a video–based infrared eye tracker using a novel method for calibration. The calibration stimuli were nine 5–degree nine–cycle square–wave radial gratings which allowed the patients to use peripheral vision in order to center their gaze on the stimuli. Prior to calibration, patients were given scotoma–awareness training using these stimuli. A calibration was considered successful if the patients' eye fixations corresponded to the size and shape of the calibration matrix when they fixated the nine calibrations points once more. Macular perimetry was obtained using a Humphrey perimeter. Results: We were able to successfully calibrate the eye tracker and to determine gaze direction for all patients. The patients' fixation locations during the acuity and perimetry tasks were analyzed in terms of quadrants and hemifields. Only two of the ten patients fixated the same quadrants in the two tasks, but seven out of the ten consistently fixated on the right hemifield. Conclusions: The calibration method employed allowed us to use an eye tracker to determine the gaze direction of patients with macular dystrophy. The preferred retinal locus (PRL) of the patients changed with the task, but certain features of their ocular motor function were common to the acuity and perimetry tasks.

Keywords: age-related macular degeneration • eye movements: recording techniques • perimetry