Abstract
Patients with central vision loss typically use a preferred retinal locus (PRL) in peripheral retina to fixate objects. Research on the use of PRLs has focused primarily on basic eye movement measures and high acuity tasks such as reading. It is not known how these findings generalize to many everyday tasks, and to what extent task affects PRL selection. We studied PRL usage during three natural tasks performed by a subject with bilateral central scotomas (∼20° in diameter) due to Stargardt's disease. The tasks included making a sandwich, building a model, and catching a bounced ball. Binocular eye movements were recorded using an Eyelink II tracking system. The subject was calibrated by centering gaze onto a large fixation cross extending beyond the scotomas. The gaze record indicated that the subject could reliably center gaze on the cross. Additionally, the calibration method was validated using a similar technique during fundus imaging. The subject's fixation patters were compared with those of normal sighted subjects. In general, the subject preferred to use PRLs in the lower left visual field quadrant. While making a sandwich or building a model, the retinal area used as a PRL varied considerably from [[lt]]10deg2 to [[gt]]100deg2 depending on the sub-task performed. Additionally, the location of the PRLs varied depending on the location of objects in the scene, relative to the body. While catching, the subject was able to peripherally pursue the ball at gains of 0.5–1.0 over part of its path. Peripherally guided pursuit could be achieved over a range of retinal locations covering [[gt]]200deg2. In summary, many retinal locations can provide the information critical for guiding the current action in natural vision. This may be a consequence of the reduced spatial resolution required to guide many actions, and the low acuity gradient in the spared retina.
Supported by NIH EY-05729 and RR06853