Fixation Stability on Central and Eccentric Targets in Patients With Age–Related Maculopathy Pre and Post Eccentric Viewing Training

Abstract

Abstract: : Purpose:To compensate for disturbances in their central vision, patients with age–related maculopathy (ARM) are often taught to use eccentric viewing (EV). Little is known however if the variability in fixation with a retinal locus of fixation varies across different areas of the visual field. The purpose of this study was to measure the variability in fixation in ARM subjects fixating on central and eccentric targets pre and post EV training. Methods:Eight ARM patients, who were participating in a blind rehabilitation program at the Hines VA Blind Center, had fixation stability on central and eccentric stimuli assessed pre and post EV training using the Rodenstock confocal scanning laser ophthalmoscope (SLO). Fixation stability with the subject’s preferred retinal location (PRL) on a central target was assessed by presenting a Goldmann III target at 0 dB near the center of the SLO display. Fixation stability on eccentric stimuli was assessed by presenting the fixation target at 4 different, eccentric points, each located approximately 7⁰ superior, inferior, nasal and temporal to the center of the display. The area over which fixations were made on both the eccentric stimuli and central target was calculated by fitting a bivariate ellipse. This was done both pre and post EV training. The variability (standard deviation) in fixations, represented by the length of the major and minor axes of the bivariate ellipses, was also calculated for the eccentric stimuli and central fixation tasks pre and post EV training. Results:The area and the length of the major and minor axes of the bivariate ellipses were larger in the central fixation task than in the eccentric stimuli fixation task. This was true both pre and post EV training, however the differences found were not statistically significant. The area and the length of the major and minor axes of the bivariate ellipses pre EV training were not significantly different from that post EV training. This was found for fixations made on both the eccentric stimuli and central targets. Conclusions:Subjects with ARM have difficulty maintaining steady, non–foveal fixation on both central and eccentric targets. These preliminary data do not support the suggestion that EV training improves fixation stability.

Keywords: low vision • eye movements • vision and action