Moderate aerobic exercise helps protect the structure and function of nerve cells in the retina after damage, say researchers at the Emory Eye Center and the Atlanta VA Medical Center, who investigated this in a mouse model of macular degeneration.
The findings, published in the February 12 issue of the Journal of
Neuroscience, are the first to suggest that aerobic exercise can have a
direct neuroprotective effect on retinal health and vision.
“This research may lead to tailored exercise regimens or combination
therapies in treatments of retinal degenerative diseases,” says
coauthor Machelle Pardue, PhD. “Possibly in the near future,
ophthalmologists could be prescribing exercise as a low-cost
intervention to delay vision loss.”
The researchers trained mice to run on a treadmill for one hour per
day, five days per week, for two weeks. After the animals were exposed
to toxic bright light to induce retinal degeneration, they exercised for
two more weeks.
The investigators found that the exercised mice had nearly twice the
number of photoreceptor cells as those that spent the equivalent amount
of time on a stationary treadmill, and their retinal cells were more
responsive to light.
The researchers were able to show that the effects of exercise come
partly from a growth factor called BDNF, which has been linked in other
studies to the beneficial effects of exercise. The exercised mice had
higher levels of BDNF in the blood, brain and retina.
The researchers also demonstrated that chemically blocking BDNF receptors negated the protective effects of aerobic exercise.
“One point to emphasize is that the exercise the animals engaged in
is really comparable to a brisk walk,” Dr. Pardue says. “One previous
study that examined the effects of exercise on vision in humans had
examined a select group of long-distance runners. Our results suggest
it’s possible to attain these effects with more moderate exercise.”
The investigators are now testing whether other exercise regimens
are even more protective, and whether exercise is beneficial for other
retinal diseases, such as glaucoma and diabetic retinopathy.
“This is a very intriguing study, and probably worth following up in
humans,” says D. Joshua Cameron, PhD, assistant professor at Western
University of Health Sciences College of Optometry, whose research also
centers on the neurobiological development of eye disease. “I would
expect that humans might require more than just a few weeks of moderate
exercise, and any changes in humans will probably be much less
pronounced [because] … the human disease generally progresses over a
much longer time-frame.”
While exercise likely would contribute to overall health, and
consequently prevent/delay disease onset—including a progressive eye
disease such as AMD—“advising any patient who can safely do moderate,
frequent exercise is likely to be beneficial to them for many health
reasons, not just eye health,” Dr. Cameron says.
Lawson EC, Han MK, Sellers JT, et al. Aerobic exercise protects
retinal function and structure from light-induced retinal degeneration. J
Neurosci. 2014 Feb 12;34(7):2406-12.