'Preferred retinal location' may aid rehabilitation in patients with central vision loss

(Press-News.org) Philadelphia, Pa. (May 28, 2013) - Perceptual learning techniques may provide a useful new approach to rehabilitation in patients with central vision loss—taking advantage of visual plasticity that persists even in old age, according to a special article in the June issue of Optometry and Vision Science, official journal of the American Academy of Optometry. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.

The paper by Susana T.L. Chung, OD, PhD, FAAO, 2012 recipient of the prestigious Glenn A. Fry Lecture Award, presents new research findings on plasticity of the visual system in older adults with central vision loss. Anthony Adams, OD, PhD, Editor-in-Chief of Optometry and Vision Science, comments: "This award-winning author explored whether the new 'preferred retinal location' (PRL) in these typically older patients adopted important properties of the original fovea and hence provide evidence that even the older brain's visual cortex shows plasticity."


Evidence of 'Visual Plasticity' in Central Vision Loss…

Patients with loss of vision in the central part of the visual field face major challenges for daily living. The most common cause is age-related macular degeneration (AMD), which is also the leading cause of blindness in older adults. Central vision loss results from destruction of the fovea— the central pit of the retina, where visual acuity is sharpest.

Patients with central vision loss have problems with tasks requiring detailed vision, such as reading and recognizing faces. Although magnification can help, "Alternative rehabilitation strategies need to be developed to improve the functional vision of people with central vision loss, which hopefully will lead to an improved quality of life," Dr Chung writes.

One potentially useful approach is "perceptual learning"—improving various aspects of sensory function through repeated practice. Perceptual learning can improve vision in younger patients with amblyopia ("lazy eye"). It was previously thought that older patients, like those with AMD, no longer had enough visual plasticity to benefit from this approach.

Dr Chung's research takes advantage of the fact that people with central vision loss often adopt another location in the macula—the so-called preferred retinal location—to perform visual tasks. She reports a series of experiments "demonstrate[ing] the presence of plasticity in the visual system after bilateral central vision loss, especially at and around the PRL."


…May Lead to New Rehab Strategies in Central Vision Loss

These results show that "The visual system for these individuals is still plastic and can be modified through experiences," Dr Chung writes. She tested this hypothesis in a preliminary study of six older adults with central vision loss. In these patients, perceptual learning techniques targeting the PRL led to an average 50 percent increase in reading speed.

However, perceptual learning can't improve visual acuity—patients still needed large-print books or magnification to see print. In addition, they would likely need continued practice in order to retain the improvement in reading speed. Dr Chung concludes, "The presence of this experience-dependent plasticity offers us an exciting opportunity to adopt perceptual learning as an alternative rehabilitative strategy for improving visual functions for people with central vision loss."

Dr. Chung received the 2012 Glenn A. Fry Lecture Award in recognition of her research contributions. This prestigious award was established by American Optometric Foundation to honor Dr. Glenn A. Fry, who contributed so much to the profession of optometry through his writings, teachings, and administrative duties at the Ohio State University.

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About Optometry and Vision Science

Optometry and Vision Science, official journal of the American Academy of Optometry, is the most authoritative source for current developments in optometry, physiological optics, and vision science. This frequently cited monthly scientific journal has served primary eye care practitioners for more than 75 years, promoting vital interdisciplinary exchange among optometrists and vision scientists worldwide.

About the American Academy of Optometry

Founded in 1922, the American Academy of Optometry is committed to promoting the art and science of vision care through lifelong learning. All members of the Academy are dedicated to the highest standards of optometric practice through clinical care, education or research.

About Lippincott Williams & Wilkins

Lippincott Williams & Wilkins (LWW) is a leading international publisher of trusted content delivered in innovative ways to practitioners, professionals and students to learn new skills, stay current on their practice, and make important decisions to improve patient care and clinical outcomes.

LWW is part of Wolters Kluwer Health, a leading global provider of information, business intelligence and point-of-care solutions for the healthcare industry. Wolters Kluwer Health is part of Wolters Kluwer, a market-leading global information services company with 2012 annual revenues of €3.6 billion ($4.6 billion).

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