We know exercise is a good thing. It improves everything from cardiovascular disease to one’s cognitive health. Observational studies have also seen physical activity lessen age-related vision loss, but until now it hasn’t been clear how causal that relationship has been. New research from the University of Virginia (UVA) is offering the first experimental evidence to show how exercise can directly slow, or even prevent, macular degeneration.
“There has long been a question about whether maintaining a healthy lifestyle can delay or prevent the development of macular degeneration,” says Bradley Gelfand, a researcher working on the new study. “The way that question has historically been answered has been by taking surveys of people, asking them what they are eating and how much exercise they are performing.”
But those kinds of studies are prone to self-reporting errors. And as Gelfand notes, even if there is an observed association between increased physical activity and reduced vision loss, it doesn’t necessarily imply a causal link. After all, as people get older and their vision declines they naturally exercise and move about less.
So Gelfand and the UVA team set up a series of mouse experiments to investigate whether exercise directly affects macular degeneration. Two groups of mice were compared, one group with an exercise wheel in the cage, and another group sans the wheel. The voluntary nature of the exercise was important as forced exercise exerts a number of stress responses that could negatively influence the results.
After four weeks the researchers used lasers to induce a form of eye damage called choroidal neovascularization (CNV), a major factor in many age-related forms of vision loss that involves an overgrowth of blood vessels in a certain part of the eye. The researchers modeled this vision loss factor in the mice through laser-induced CNV.
Across two experiments the researchers discovered blood vessel overgrowth in the exercising mice was between 32 and 45 percent lower than in the mice without access to voluntary exercise. Even more interesting was the finding that exercising following the laser injury did not improve CNV damage. Only the mice with the pre-conditioning of exercise displayed reductions in the subsequent eye damage.
This all ultimately goes to suggest a small amount of exercise does seem to offer direct preventative outcomes against certain types of degenerative vision loss. Exactly what specific molecular mechanism is mediating this macular protection is still unclear. One hypothesis raised suggests exercise confers immunomodulatory effects that can reduce possible inflammatory actions underpinning age-related macular degeneration.
The research team hopes to further investigate the key mechanisms at play with a view to developing some kind of pharmaceutical treatment to mimic this natural process.
“The next step is to look at how and why this happens, and to see if we can develop a pill or method that will give you the benefits of exercise without having to exercise,” Gelfand said. “We’re talking about a fairly elderly population [of people with macular degeneration], many of whom may not be capable of conducting the type of exercise regimen that may be required to see some kind of benefit.”
The new study was published in the journal Investigative Ophthalmology & Visual Science.
Age-related vision loss prevented by exercise in experimental study [New Atlas]