The two forms of age-related macular degeneration progress at different rates. The wet form of the disease progresses faster than the dry form. Still regardless of the type, once someone is diagnosed with age-related macular degeneration, that person can expect a decline in vision to take place gradually over the course of five years. In its early stages, age-related macular degeneration only affects night vision. In the intermediate stage, it affects daytime vision. In the late state, it affects the ability to read and recognize faces.
While there are treatments, such as anti-vascular endothelial growth factor (anti-VEGF) therapy for the wet form of the disease and the newest treatments for the wet form of the disease, aflibercept (Eylea) and ranibizumab (Lucentis); the problem is knowing when to “pull the trigger” and start treatment. With anti-VEGF therapy, patients need to reach a certain vision threshold before benefit of the therapy outweigh the risks. As for Eylea and Lucentis, they aren’t cheap. They cost $2000 per injection. They are covered on Medicare Part B but patients have to first meet the deductible and then pay 20 percent of the injection cost.
Because of these obstacles, researchers are looking for ways to identify and assess what disease stage the patient is in and develop the correct treatment plan. Here is what researchers have learned in this area.
Night Vision Tests
Cynthia Owsley PhD and Christine Curcio PhD of the University of Alabama at Birmingham found that night vision tests at a specific spot on the retina could be utilized to assess treatments for age-related macular degeneration. They lead the National Eye Institute (NEI) funded project, Alabama Study on Early Age-related Macular Degeneration (ALSTAR2). This project assessed over 500 people over a three-year period to ascertain the best vision test for indicating both disease onset and worsening.
Since reading and other bright-light visual tasks require the use of cone photoreceptors concentrated in the fovea, a part of the retina that doesn’t have rod photoreceptors, this study showed that, despite being few in number, the rod photoreceptors next to the fovea are stronger indicators than the more numerous rods that are farther away.
After experiencing a bright flash of light, the rods in the near the fovea take time to recover. The older someone is, the longer it takes for the rods to recover and more so in someone who has age-related macular degeneration. Knowing that the increase in recovery time is worse near the fovea links vision changes to certain cellular mechanisms. So, researchers think that a lifetime of maintaining the cone photoreceptors has damaged the tissues that support the rod photoreceptors. Whether this increase in recovery time actually predicts disease progression, will be studied during the three-year follow up vision of the ALSTAR2 study.
Part Two will be discuss the use of AI and fundus photos to show the progression of age-related macular degeneration.