'Preferred Retinal Location' Benefits Older Patients with Central Vision Loss
Individuals with loss of vision in the central part of the visual field encounter major challenges in their daily life. 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 in the retina, where visual acuity is the sharpest.
Patients suffering with central vision loss have difficult with tasks that require detailed vision, such as reading and recognizing faces. Although magnification can be helpful, Dr. Susana Chung, OD, PhD, writes, "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.”
One potentially helpful approach is “perceptual learning” – improving various aspects of sensory function through repeated practice. Perceptual learning can boost vision in younger patients with amblyopia or lazy eye. It was previously believed that older patients, like those with AMD, no longer had sufficient visual plasticity to benefit from this approach.
Dr. Chung’s research takes advantage of the fact that individuals with central vision often adopt another location in the macula – the so-called preferred retinal location – to perform visual tasks. She reports a series of experiments, “demonstrating the presence of plasticity in the visual system after bilateral central vision loss, especially at and around the preferred retinal location."
Dr. Chung writes, “These findings demonstrate that the visual system for these individuals is still plastic and can be modified through experiences.” She tested her hypothesis in a preliminary study of six older adults who had central vision loss. For these patients, perceptual learning techniques targeting the preferred retinal location led to an average 50 percent rise in reading speed.”
However, it’s important to note that perceptual learning can’t improve visual acuity – patients still require large-print books or magnification to see print. Additionally, they would likely need to continue practicing in order to retain their improvements 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."