There’s an intriguing article in the January 2022 Berkeley Wellness Letter that looks at a number of meta-studies about the relationship between exercise and cataracts, glaucoma, and macular degeneration. The evidence shows that being physically active may be a key step to preventing or delaying the progression of these three very different eye diseases.
A meta-analysis in the International Journal of Ophthalmology in 2020, which included six studies involving more than 170,000 people, found that those who said they engaged regularly in physical activity were 10 percent less likely to develop cataracts over six to twelve years than those who were mostly inactive. This could be because exercise can improve the body’s ability to recover from oxidative damage, or it might be because exercise can inhibit inflammation, which is a known cause of cataracts.
This condition is marked by damage to the optic nerve, usually as a result of pressure buildup in the eye (called intra-ocular 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. Over the next six years, those who exercised moderately at least 150 minutes per week or vigorously at least 75 minutes per week were 47 percent less likely than their inactive peers to develop glaucoma.
Some experimental evidence suggests that exercise may protect against glaucoma over time by decreasing intraocular pressure, which protects the optic nerve from damage.
Keep in mind that people with glaucoma should generally avoid exercises in which the head is below the heart, like doing a headstand, which can temporarily increase intra-ocular pressure. Check with your eye doctor if you’re not sure about the safety of a particular exercise.
Age-related macular degeneration (AMD)
AMD 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. A meta-analysis of nine studies involving more than 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 over follow-up periods than people who were most active.
Physical activity had less 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 anti-oxidant enzymes and by boosting cells’ resistance to oxidative stress.
Note that all of these studies show relationships, or associations, but do not 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, even though the authors did attempt to control for such factors in their analysis.
Regardless of whether exercise alone can prevent cataracts, glaucoma, or AMD, there are many other good reasons to be physically active. Exercise is obviously not a cure-all for everything, but most of us would do well to do more. So, get (or stay) moving and consider potentially better vision an extra perk.