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Diabetic Eye Disease: What You Need to Know
If you have been diagnosed with diabetes, you may be at risk for developing many different types of eye problems, including diabetic retinopathy, cataract, secondary glaucoma, macular damage and changes in refraction. Because the disease involves blood vessels and nerves, adults who have had long-term diabetes may experience damage to the eyes, particularly if control of blood glucose has been sporadic.
People with diabetes should never ignore visual problems, no matter how mild, because they could be an indication of a more serious problem. Early diagnosis and treatment can reduce vision loss. Some symptoms may be corrected with standard prescription lenses, while others may need medication or surgery.
Diabetic Retinopathy
Diabetic retinopathy is the main cause of vision loss in adults ages 45 to 65. Worldwide, 2.5 million people experience vision loss due to diabetic retinopathy (International Diabetes Federation, 2002). About 40 percent of people with diabetes will have at least mild retinopathy. Incidence increases with the disease's duration and when there is inconsistent control of blood glucose. Retinopathy is characterized by leakage of fluid or blood from vessels in the retina.
Retinopathy can cause blurred or hazy vision, particularly if the disease has progressed to retinal hemorrhages or edema (swelling) of the macula.
Although the presence of retinopathy can be detected by looking into the eye, details are best identified by injecting a fluorescent dye into the bloodstream. This allows the ophthalmologist to photograph and evaluate the retinal blood vessels, and to pinpoint areas that are leaking due to neovascularization (growth of fragile new blood vessels).
If such areas are found in the peripheral retina, laser treatment (panretinal photocoagulation) is recommended to seal off leaking vessels and destroy abnormal ones. If there is macular edema, scattered laser treatment in the macula may be recommended. In some cases, early treatment may restore vision, stabilize it or, at least, delay severe loss of sight.
Cataract
Diabetes increases the possibility of cataract, a clouding of the transparent lens of the eye. Cataract may cause hazy vision and glare sensitivity. If retinopathy has not damaged the retina, surgical removal of a cataract usually results in improved vision. If there is damage to the retina, the cataract may still be removed in order to improve the ophthalmologist's view of the retina. This makes it easier to evaluate the condition of the eye prior to laser treatment. When a person with diabetes has a cataract operation, standard surgical techniques are used.
Secondary Glaucoma
Fragile new blood vessels in the eye of someone with diabetes may form a new network directly on the iris, blocking the outflow of fluid from the eye. This condition, called secondary glaucoma, results in elevated pressure of the fluids within the eye, and can cause optic nerve atrophy and loss of the full visual field. Treatment involves the application of laser to the leaking areas. Standard glaucoma treatment with drops or diuretics may also be recommended to lower intraocular pressure.
Macular Damage
In chronic macular edema, faulty color vision may result and usually is irreversible. Even after the macula has been treated with laser, there may still be problems reading because of distortion. Low vision magnifying devices may be needed.
Changes in Refraction
High blood glucose levels that are characteristic of poorly controlled diabetes can also result in changes in refraction (the accurate focus of light rays on the retina). This is due to swelling of the lens, which causes myopia (near-sightedness). Before such transient refractive changes are corrected by standard prescription eyeglasses, improved control of blood glucose should be attempted. Glasses should be prescribed only after blood glucose has stabilized, or consecutive examinations reveal consistent refractions.
Reducing the Risk of Vision Loss Due to Diabetes
If you have already been diagnosed with diabetes, visits to the eye doctor at least once a year to test for diabetic retinopathy and other eye diseases are critical. According to the National Eye Institute, research suggests that the risk of diabetic retinopathy can be reduced through careful control of blood sugar, which your doctor can help you manage.