The Complications of Age-Related Macular Degeneration Prevention Trial (CAPT) Research Group assessed night vision in a cohort of 1,052 CAPT patients. The main purpose of CAPT, a National Eye Institute-sponsored multicenter randomized clinical trial conducted from 1999 to 2005, was to investigate whether low-intensity laser treatment could prevent vision loss in patients with early stage age-related macular degeneration (AMD).
In advanced stages, AMD destroys the macula in the eye's retina, the area that normally provides the detailed, central vision we rely on for reading, driving and other daily tasks. The CAPT results did not show that the laser treatment prevented vision loss, but data from the CAPT cohort did identify a new way to predict AMD progression.
Earlier studies had shown that loss of photoreceptor (light sensitive) cells, particularly "rod" cells involved in night vision, occurs before the disease progresses to advanced AMD in the retina, which indicated that assessing night vision might be a good way to track AMD progression. In the CAPT, patients with signs of early AMD, defined as 10 or more large deposits known as drusen on the retina and vision 20/40 or better, initially completed a 10-item night vision self-assessment questionnaire that rated difficulties with night driving and problems with vision deficits during low-light activities like reading or watching movies.
The patients were followed-up annually up to five or six years. Data analyses led by Gui-shuang Ying, PhD, showed that those who had the worst night vision at baseline were the most likely to develop geographic atrophy (GA), or choroidal neovascularization (CNV) and to experience reduced visual acuity. GA is also known as advanced "dry" AMD, and CNV as "wet" AMD.
Since the association of night vision symptoms and AMD progression is clear and the 10-item questionnaire is simple and inexpensive to administer, Dr. Ying concludes that this could be a useful way for ophthalmologists to identify patients at high risk and intervene early to prevent vision loss and the progression to advanced AMD.
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