Cataracts, glaucoma, and age-related macular degeneration (AMD) are the three leading causes of vision loss in older adults in the U.S. Although each disorder has unique risk factors, growing research suggests they share a common thread: As with so many other diseases, being physically active may be a key step to preventing them or delaying their progression.
Here’s a peek at the evidence from some observational studies spanning the last 15 years. Keep in mind that the studies described here show relationships, or associations, but don’t establish cause and effect. There may be other reasons that physically active people have healthier eyes—for example, they may be more likely to have good eating habits, visit the doctor regularly, and have access to high-quality health care, or be less likely to smoke or drink alcohol to excess, although the authors attempted to control for such factors in their analyses.
Cataracts
In this common age-related condition the eye’s normally clear lens becomes cloudy, eventually leading to blurry vision and other vision changes. In a study in Ophthalmology in 2015, researchers analyzed data from more than 52,000 men and women, ages 45 to 83 and all initially free of cataracts. Over an average of 12 years, those in the highest quartile of physical activity at the start of the study were 13 percent less likely to develop cataracts than those in the lowest quartile. Highly active individuals who had also been active earlier in life (at age 30) saw an even greater benefit—a 24 percent reduced risk of cataracts, compared to people who were inactive both as younger adults and at the time of the study. Among specific activities, biking or walking more than an hour a day, or working in a job that involved heavy manual labor, were associated with lower cataract risk than rarely biking or walking or having a job that involved mainly sitting. In contrast, spending more than six waking hours a day being inactive (sitting or lying down) was linked with substantially higher cataract risk than being sedentary less than an hour a day.
Similarly, a meta-analysis in the International Journal of Ophthalmology in 2020, which included six studies involving more than 170,000 (initially cataract-free) people, found that those who said they regularly engaged in physical activity at baseline were 10 percent less likely to develop cataracts over six to 12 years than those who were mostly inactive.
It’s known that cataract development is associated with oxidative damage, also called oxidative stress, in the lens of the eye and that physical activity (when not done excessively) can improve the body’s ability to recover from oxidative damage. Exercise is also one of many processes that can inhibit inflammation, which is a known cause of cataracts.
Glaucoma
This condition is marked by damage to the optic nerve that transmits nerve impulses to the brain, usually as a result of pressure buildup inside the eye (called intraocular pressure). In a study in Medicine & Science in Sports & Exercise in 2018, the investigators followed almost 10,000 adults, all initially free of glaucoma, who self-reported their physical activity and took a treadmill test to determine their aerobic fitness level at the start of the study. Over the next six years, those who exercised moderately at least 150 minutes per week or vigorously at least 75 minutes per week (or an equivalent combination of the two) were 47 percent less likely than their inactive peers to develop glaucoma. Being in the top third of aerobic fitness was also independently linked with lower glaucoma risk compared to being in the bottom third.
A smaller study in Ophthalmology in 2019, in which 141 older adults with diagnosed or suspected glaucoma wore an activity tracker for a week, found that for every additional 1,000 steps, 10 more minutes of moderate-to-vigorous exercise, or 30 more minutes of non-sedentary time per day, the rate of vision field loss over the next several years slowed significantly. An extra 5,000 steps a day or 2.5 hours of non-sedentary activity was associated with about a 10 percent reduction in the rate of visual field loss, the researchers reported.
Some experimental evidence suggests that exercise may protect against glaucoma over time by decreasing intraocular pressure, which protects the optic nerve from damage. It’s also hypothesized that exercise induces various biological changes that are beneficial in preventing glaucoma. For instance, some lab and human studies have found that exercise is linked with increased release of a growth factor protein (called brain-derived neurotrophic factor, or BDNF) that might help stave off the degeneration of retinal ganglion cells (a type of cell in the optic nerve).
Note that people with glaucoma should generally avoid exercises in which the head is positioned below the heart, which can temporarily increase intraocular pressure; those include “head-down” yoga poses such as downward dog, standing forward bend, and headstand. Lifting heavy weights should be avoided for the same reason. If you aren’t sure about the safety of a particular exercise, check with your eye doctor.
Age-related macular degeneration
This condition affects the macula—the central, most critical part of the retina for sharp vision—and is the leading cause of severe and irreversible loss of central vision in people older than 50. Back in 2006, a study in the British Journal of Ophthalmology, which followed 3,874 adults ages 43 to 84 over 15 years, found that those who had active lifestyles (defined as engaging in an activity for long enough to work up a sweat at least three times a week) were 70 percent less likely than those with sedentary lifestyles to develop the “wet” form of AMD, the less common but more serious type. In addition, walking more than 12 city blocks per day on average was associated with a 30 percent lower wet AMD risk compared to walking less.
More recently, a meta-analysis of nine studies involving nearly 41,000 adults of all ages, published in 2017 in the American Journal of Ophthalmology, found that those who did at least three hours of low-to-moderate-intensity exercise a week were 41 percent less likely to develop late-stage AMD (which involves substantial vision loss) over follow-up periods ranging from six to 20 years than people who were less active. Physical activity had a smaller effect on early-stage AMD, reducing risk by 8 percent.
As with cataracts, physical activity might reduce the risk of AMD by increasing the activity of antioxidant enzymes and by boosting cells’ resistance to oxidative stress, which is involved in both aging and likely the progression of AMD.
BOTTOM LINE: Regardless of whether exercise alone can prevent cataracts, glaucoma, or AMD, there are many other good reasons to be physically active. So get (or stay) moving, and consider potentially better vision an extra perk.
