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Consistency of Preferred Retinal Locus Across Tasks in Participants Trained With a Simulated Scotoma
January 3, 2023
Posted in PracticeUpdate, Written by Bruce P. Rosenthal OD, FAAO, Lighthouse Guild, Chief of Low Vision Services
The prevalence of age-related macular degeneration (MD) continues to increase throughout the United States (2019: approximately 20 million) and Western Countries (by 2040: 248 million). MD, particularly owing to the progressive nature of this condition, may significantly decrease the visual function in affected individuals and compromise their ability to continue working, reading, driving, or traveling independently. MD may also result in depression and, most importantly, reduced quality of life or loss of independence.
However, the authors of the “Consistency of preferred retinal locus across tasks and participants trained with a simulated scotoma” study noted that an individual with MD might retain more functional vision than expected. Patients may autonomously develop compensatory strategies, including the development of a preferred retinal locus (PRL). The PRL effectively seeks to replace the compromised fovea, especially around a scotoma that may have developed. Additionally, the authors were also interested in determining whether there were perhaps multiple and different PRLs for task requirements.
The participants chosen for the study were 19 healthy individuals who were trained for 10 sessions using a gaze-contingent, simulated central vision loss by a scotoma obstructing the central 10 degrees of their visual field.
The authors noted that the overall PRL left–right bias was consistent with the idea that PRL selection by the participants resulted in identifying locations with better sensitivities (performance-driven selection). Other findings revealed that there were different PRLs for different tasks. One example was that patients tended to use PRLs closer to the fovea or scotoma and had better fixation stability for brighter stimuli.
It was also noted that the results represent one of the first examinations of peripheral viewing strategies across simulated vision loss and may help model visual pathologies, such as MD.
High on the list of persons affected by MD is being able to read and access information. The study provides an opportunity to discuss the positive findings with patients who are considering a PRL or multiple PRLs to aid with reading.
Furthermore, clinicians are also fortunate to have access to modern technologies to better understand the concept of a PRL or multiple PRLs. The OPTOS high-resolution retinal imaging system, microperimetry with the Macular Integrity Assessment, or optical coherence tomography, among others, provide important information for helping the patient understand the best strategies for moving forward and being able to read.
Discussing the PRL would also help patients better understand why an electronic device, such as a portable CCTV, would be of greater benefit in providing magnification and the ability to improve contrast.
In summary, the compensatory strategies of the PRL or multiple PRLs to replace the compromised fovea affords an opportunity for patient education and methods to enable them to access news and information and improve their quality of life.
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