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Dry AMD inhibits visual localization
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Computer simulation of everyday visual tasks showed that people with dry age-related macular degeneration are likely to experience difficulties in localizing objects even at the less severe stages of measurable visual impairment.
Participants were recruited from the Moorfields Eye Hospital Trust and other databases in London and were required to have dry AMD with visual acuity of 20/100 or better. A total of 31 AMD patients and 33 healthy controls were included.
Three practice images and 15 test images were displayed on a computer screen, and participants were instructed to localize specific objects within an everyday indoor or outdoor scene and indicate verbally when the object was found. Eye movements were recorded using the Eyelink II system (SR Research Ltd.) to verify the subject’s point of regard and to measure eye movement parameters.
Average search duration was almost double for AMD patients as compared with controls and in most cases fell out of the normal limits for the task. It is noteworthy, as the authors pointed out, that “average visual acuity in the AMD group, although reduced, fell within the U.K.’s legal requirements for driving.”
Although no difference was found in fixation duration and saccades per second, people with AMD had statistically significantly smaller saccadic amplitude than controls.
Visual search is a critical part of performing daily activities. Therefore, according to the authors, these findings show that people with intermediate AMD and less severe vision impairment “may have more difficulties with these sorts of activities than previously believed.”
They suggested that real-life task simulation should support clinical measurements in the evaluation of patients with AMD. – by Michela Cimberle
Disclosure: Taylor reports no financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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