Orientation of the preferred retinal locus (PRL) is maintained following changes in simulated scotoma size

Abstract

Although macular lesions often enlarge, we know little about what happens when the preferred retinal locus (PRL) is enveloped by the lesion. We present a prospective study of subjects with normal vision who were trained to develop a PRL using simulated scotomas with a gaze-contingent visual display. We hypothesized that, when subjects had developed a robust PRL and the scotoma size was increased, the PRL would move to remain outside the scotoma and in a direction that maintained the orientation (theta) of the PRL relative to the fovea. Nine subjects with normal vision were trained to develop a PRL and were then exposed to scotoma sizes that ranged from 4°to 24°in diameter. Subjects tracked a stimulus using saccades or smooth pursuits. Fixation stability was measured by calculating the bivariate contour ellipse area (BCEA). To measure the reassignment of the oculomotor reference (OMR) to the PRL, we analyzed the spread (BCEA) of saccade first landing points. All subjects developed a robust PRL that did not vary more than 0.8°on average between blocks of trials of a scotoma size, and they maintained the orientation of the PRL as the simulated scotoma size varied (±9°median standard deviation in theta, defined as orientation angle). Fixation stability and OMR to the PRL worsened (larger BCEA) with increasing scotoma size. This, and related studies, could guide development of a PRL training method to help people with central vision loss.

Simulating Macular Degeneration to Investigate Activities of Daily Living: A Systematic Review

“…Specifically, studies were excluded if their main focus was on oculomotor behavior (eye movements) and/or vision assessments. Simulation research of this nature is highly informative about fixation and saccade patterns, and the implications of these patterns for the development of a preferred retinal locus or eccentric fixation (Kwon et al, 2013;Costela et al, 2020). However, studies like these do not directly collect data on performance-based measures (e.g., sorting medications) of everyday activities that can immediately inform researchers about the struggles of living with AMD.…”

“…In terms of the length of adaptation periods, researchers have yet to come up with a standard that can be applied in future studies. Studies examining oculomotor strategies have differed in their approaches to inducing a preferred retinal locus in normally sighted participants; training sessions have been conducted over the course of hours, days, or weeks (Kwon et al, 2013;Costela et al, 2020;Maniglia et al, 2020;Prahalad and Coates, 2020). This demonstrates a lack of consistency in how long is considered suitable to reasonable compensate for central vision loss.…”

“…The convenience of control has also been advantageous during investigations into adaptive strategies to loss of central vision (e.g., preferred retinal locus; Barraza-Bernal et al, 2018). This phenomenon may occur if the fovea is damaged during AMD progression (Costela et al, 2020). While not analyzed within this review, simulation research has significantly contributed to our understanding of how a preferred retinal locus can be induced, relocated, or sustained (Kwon et al, 2013;Barraza-Bernal et al, 2017).…”

Saccade Landing Point Prediction Based on Fine-Grained Learning Method

“…Gaze-contingent displays [ 1 ] have been used in video streaming [ 2 ], [ 3 ], robot-assisted surgery [ 4 ], human-computer interfaces for new virtual reality environments [ 5 ], reading research [ 6 ] and simulation of impaired vision [ 7 ], [ 8 ], among others. These systems allow researchers to investigate a variety of visual phenomena, including eye movement guidance in reading, stability of vision, visual search strategies, and scene perception.…”

Table_1.DOCX

“…Recently, a new approach has been developed that uses eye tracking-based simulation of central vision loss in normally seeing individuals as a lab-based model system to study vision in the presence of a central scotoma, in particular oculomotor strategies, PRL development, and clinical interventions in controlled environment (Bertera, 1988;Fine and Rubin, 1999;Pidcoe and Wetze, 2006;Aguilar and Castet, 2011;Kwon et al, 2013;Walsh and Liu, 2014;Liu and Kwon, 2016;Barraza-Bernal et al, 2017a,b;Chen et al, 2019;Maniglia et al, 2019Maniglia et al, , 2020aCostela et al, 2020;Xie et al, 2020). In this framework, an opaque occluder of a few degrees radius is generated and controlled by a computer connected to an eye tracker to obstruct central vision in real time.…”