Abstract
Abstract: :
Purpose: The aim of this work was to measure fixation stability in patients with central visual field defects and to relate the results with the size and location of the scotoma. Methods: Eye–position data were recorded from observers with a modified infra–red xy–gaze–tracking device using the pupil and corneal reflection (iView, SensoMotoric Instruments GmbH; sampling rate 60 Hz; angular resolution 0.2 deg). Patients were instructed to fixate a static target for 60 seconds. The task was performed by 10 patients with Stargardt or cones degeneration and by 10 normals. The patients had visual acuity in the range 0.7–1.0 Log MAR. Eye–position data were analysed by estimating the area of the corresponding bivariate contour ellipses. Results: Although a significant inter–observer variability was found for patients, their fixation areas were significantly larger than for normals. Some patients, however, with very small residual central vision had normal fixation. Conclusions: Patients with central visual scotomas have impaired fixation stability but small residual central vision may have an important role in preserving normal fixation.
Keywords: low vision • eye movements • visual fields