Eye Health and Diabetes

Diabetes is the leading cause of new cases of blindness among adults aged 20 to 74 years. Diabetic retinopathy causes 12,000 to 24,000 new cases of blindness each year (43). People with diabetes can maintain optimal vision and healthy eyes by having an annual comprehensive vision examination, including a dilated eye examination, with early intervention if retinopathy is found.

Diabetes-related Eye Conditions

People with diabetes are at 25 times greater risk for blindness (44). People with diabetes who smoke, have poor nutrition, and do not control their diabetes have an even greater risk of developing eye complications. Because many people with diabetes have slower healing time, eye injuries—even minor corneal scratches—should not be taken lightly.

Retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes. Elevated blood sugar damages the retinal blood vessels, causing them to break down, leak, or become blocked. Over time, this causes retinal hemorrhage and impaired oxygen delivery to the retina that can lead to the growth of abnormal vessels. These new vessels are fragile and can break easily, causing permanent vision loss. One in 12 people with diabetes aged 40 years and older has vision-threatening diabetic retinopathy (45). Studies have shown that aspirin use (e.g., for CVD prophylaxis) is safe in persons with retinopathy and has no adverse effect on the development or progression of diabetic retinopathy (46, 47).

Poor glycemic control and longer duration of diabetes lead to increased rates of retinopathy in people with type 1 and type 2 diabetes. Diabetic retinopathy, however, is treatable, and one of the most preventable causes of vision loss and blindness. The risks of DR are reduced through disease management of blood sugar, blood pressure, and lipid control. Early diagnosis and proper treatment reduce the risk of vision loss; however, as many as 50% of patients are not getting their eyes examined or are diagnosed too late for treatment to be effective. Individuals with diabetes are also at an increased risk for glaucoma and cataracts.

Early detection and treatment can prevent or delay blindness due to diabetic retinopathy in 90% of people with diabetes. Good glycemic control has been shown to reduce or delay by 76% the development of retinopathy in people with diabetes (47). Intensive therapy reduces the first appearance of any retinopathy by 27%. Retinal laser photocoagulation surgery can reduce the risk of severe vision loss from the worst form of the disease, proliferative diabetic retinopathy (PDR), to 4% percent or less (48).

Optometrists and ophthalmologists can provide low-vision aids—from simple hand magnifiers to innovative optical devices—to help those who have experienced uncorrectable vision loss due to diabetic retinopathy. These eye care professionals can additionally provide or assure the provision of a full spectrum of care and services that may allow people with vision impairment and diabetes to maintain their independence and quality of life and help control their diabetes (e.g., to read instructions, take medication, continue with household tasks).

Other Common Eye Complications in Diabetes

Cataracts are a clouding of the eye lens most often caused by aging. The lens is responsible for focusing the images onto the retina, and thus a clouding of the lens can result in diminished vision and increased sensitivity to glare. Over half of all Americans aged 65 years and older have cataracts (3).

Glaucoma is a progressive disease that damages the optic nerve. It is this
nerve that carries the retinal image to the brain, so disruption of this transmission can cause irreversible blind spots or field loss, which over time can lead to total blindness. A view of the optic nerve during a dilated eye exam, combined with visual field testing, intraocular pressure testing (IOP), and other tests can often reveal damage at an early stage, thus providing opportunity for treatment. It is important to note that IOP should never be used as a sole diagnostic indicator. Among Americans aged 40 years or older, 2.2 million have glaucoma and another 1.1 million are unaware of having the disease (46). For this reason, glaucoma often is referred to as the “silent thief of sight.” Glaucoma is twice as common among older black adults as among whites.

Double vision. People with diabetes may complain about sudden onset of double images. Because this can be due to damage to the nerves from the brain to the eye, it is important to see an optometrist or ophthalmologist immediately. This symptom can be misinterpreted by the patient or by a non-eye care provider unfamiliar with this ocular complication as a sign of a stroke or other neurological problem, prompting unnecessary diagnostic procedures such as radiological exams. Double vision (or diplopia) may instead be due to mononeuropathy—damage to a single nerve—usually cranial nerves III, IV, or VI. The sixth and third nerves are most frequently affected. Third-nerve palsies occur with pupillary sparing in 80% of cases. Most diabetic third-nerve palsies usually resolve spontaneously within 2 to 3 months and the symptom of double vision can often be controlled with the use of special lenses.

Vision fluctuation. Poor control of blood glucose levels can lead to a fluctuation in vision. These temporary visual fluctuations occur because of fluid imbalance in the crystalline lens. When the glucose level is elevated, the lens thickens, causing vision changes that may increase nearsightedness or farsightedness. When the glucose level returns to normal, the lens can shrink back to its normal state. For those who need glasses, if the glucose level is poorly controlled, the constant state of flux can make it difficult to determine the best lenses.

May 2007

National Diabetes Education Program (NDEP)    http://ndep.nih.gov
NIDDK, National Institutes of Health, Bethesda, MD

A Joint Initiative of the National Institutes of Health and the
Centers for Disease Control and Prevention