If you have diabetic retinopathy, blood vessels in your eye can swell, leak, and even bleed.

Although you may be concerned that exercise can affect your eyes, neither aerobic exercise nor strength training have been shown to worsen vision, retinopathy, or eye swelling in people with moderate vision problems, according to exercise guidelines published by the American Diabetes Association in 2006.

However, "if you're in an exercise program and have diabetes eye complications, you have to keep up with scheduled eye exams, check your regimen with your eye-care specialist, and report any problems," says A. Paul Chous, an optometrist with a specialty in diabetes who is based in Tacoma, Wash.

"Retinopathy is often more severe in people with high blood pressure and might be exacerbated by a sudden increase in blood pressure, which can occur during some exercises such as weight lifting," says Dr. Chous. "Exercise experts with training in diabetes care can advise you on what is safe and what is not, if you have complications."

Patients with significant eye complications caused by diabetes are also advised to avoid kickboxing and other contact sports that could injure the eye, as well as anything that elevates blood pressure, such as weight lifting or sprinting.

Many patients who have had laser surgery to stabilize blood vessels in the eye are advised to avoid vigorous exercise and contact sports until there's evidence that the laser treatment was effective, which can take several months, says Dr. Chous. Exercise decisions should be made on a case-by-case basis with the ophthalmologist treating the patient.

All sports enthusiasts, with diabetes or not, should wear eye protection (such as sports goggles) to prevent eye injury, say Dr. Chous, especially while doing an activity in which something—fingers or sports equipment—could strike and injure the eye.