How Blood Sugar Damages the Eye in Diabetes

Blood vessels in the eye can weaken and leak fluid and blood into the retina.
High blood sugar is toxic to many parts of the body, and the eyes are no exception. Indeed, people with diabetes are 25 times more likely to go blind than those who do not have the disease. But it's not just blood sugar. High blood pressure is also a huge factor.

The United Kingdom Prospective Diabetes Study found that people with type 2 who maintained "tight" blood pressure control—averaging 144/82—reduced their risk of vision loss by 47% and cut their risk for progression of diabetic retinopathy, the leading cause of blindness in adults, by 34%.

Regular eye exams are important
When it comes to vision-related complications of diabetes, prevention is the key, says Sean F. Murphy, MD, an ophthalmologist with the Eye Care Institute in Louisville, Ky.

"Diabetic damage is kind of like going down the stairs. Wherever you are, our first goal is to kind of dig in ... and if we can improve things, that's great," he says. "But most of the time we cannot push you back up the stairs. So the sooner someone gets in and gets diagnosed and gets treatment and gets watched, the less damage that occurs (and) the better you can do."

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There are two types of diabetic retinopathy and they usually affect both eyes similarly, according to the Mayo Clinic.

  • Nonproliferative diabetic retinopathy
    In this condition the walls of blood vessels in the retina begin to weaken, sometimes leaking fluid and blood into the retina. Often there are no symptoms early on, and even later in the disease, damage may progress without warning.

    "It's insidious, and that's the importance of the eye exam," stresses Dr. Murphy. "You can be fine, you can see 20/20 and have horrendous disease in your eyes and not know it." In fact, Dr. Murphy adds, the mere presence of symptoms often means the damage is done.

    You may experience blurred vision, for example, as the macula, the part of the retina that provides sharp, central vision, swells from leaking fluid. This condition, known as diabetic macular edema, is more likely to occur as diabetic retinopathy progresses.

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Last Updated: April 07, 2008

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