Abstract
Purpose :
The loss of the central visual field in macular disease means that patients must use peripheral vision to conduct most visual tasks. With time, most patients develop a preferred retinal locus (PRL) outside of their scotoma for visual tasks. To date, it is unclear how the PRL develops, especially in response to asymmetric progression of the disease in the two eyes. This study investigated how participants with normal vision develop a “PRL” in response to simulated bilateral central field loss; in particular, when the field loss is asymmetric in the two eyes.
Methods :
We simulated central field loss with a gaze-contingent paradigm by tracking participants’ gaze position as they performed a training task viewed through a stereoscope, and occluding a 2 degree circle around their gaze positions (the artificial scotoma) on the computer screens. Training consisted of repeated trials of identifying the orientation of a Tumbling-E. Participants performed multiple days of training. Oculomotor responses, including fixation stability, saccade latency and accuracy, were continuously monitored. To simulate the asymmetric progression of macular disease, we increased the size of the scotoma to 4 degrees in one eye after participants’ oculomotor responses to the bilateral artificial scotoma reached a plateau.
Results :
Participants’ gaze positions were analyzed using a kernel density estimator to determine the location of the “PRL”, defined as the most probable stimulus location relative to central gaze position. Each participant’s “PRL” was initially within the scotoma, but over time shifted outside the artificial scotoma (regression coefficients for time and distance were positive, p < .03). When the size of the scotoma was increased in one eye, the distance between the PRL and central gaze did not increase with time like in the first phase of training, indicating that participants did not change the location of the PRL in response to binocular asymmetry.
Conclusions :
Participants with normal vision are able to shift their “PRL” from central vision to outside a scotoma in response to bilateral simulated central field loss. Subsequent changes in the size of a scotoma, causing a binocular asymmetry, have little effect on the distance of the “PRL” from central vision. This finding suggests that the location of a PRL for patients with bilateral macular disease is likely governed by the better eye.
This is a 2021 ARVO Annual Meeting abstract.