ASSESSMENT OF FIXATION STABILITY IN NORMAL SUBJECTS AND PATIENTS USING A SCANNING LASER OPHTHALMOSCOPE

1. In this study we have investigated the ability of normal and low vi sion subjects to (a) fixate stationary targets and (b) to maintain fix ation on a stationary target while text was scrolled at different reti nal locations. 2. Test stimuli were visualized directly on the fundus with the scanning laser ophthalmoscope (SLO), and relative eye movemen ts were evaluated using digitized images. Target arrays consisted of s ingle and multiple letters which were either stationary or scrolled in a horizontal direction. The retinal area selected by the subject to v iew the target was determined, and the stability of fixation calculate d as a bivariate contour ellipse area (BCEA). 3. The ability to mainta in steady fixation varied between individuals; this variability was pa rticularly notable in the low vision patients. In the normal group, fi xation was affected by the size of the stationary target but not by th e form or polarity. In both the normal and patient groups stationary t argets allowed more accurate fixation compared to scrolling text. The speed of scrolling text and the retinal location did not influence fix ation stability.