by Dana McGinn, MD
Diabetes mellitus is an abnormality in the body’s ability to use and store sugar properly. High blood sugar levels can have a profound affect on blood vessels throughout the vascular system. Some of the earliest functional problems are manifested in the retina, the nerve layer in the eye that receives light and sends images to the visual cortex in the brain. This vessel damage is referred to as diabetic retinopathy.
The two types of retinopathy are: non-proliferative (NPDR) and proliferative (vessel growing) (PDR.)
NPDR is generally called background retinopathy and as a rule does not initially affect the vision unless the macula (the best vision portion of the retina) is involved. PDR is abnormal vessel growth (neovascularization) on the surface of the retina, iris or optic nerve. The changes occur because of widespread closure of retinal capillaries which alters normal blood flow and decreases oxygen for the retina. These new vessels do not supply nourishment and can bleed into the eye cavity, create scarring, retinal detachment, and grow on the iris (the colored front of the eye) which may cause intractable glaucoma.
A medical eye evaluation with dilation of the pupil is the only way to determine if there are diabetic changes in the eye. Additional testing can determine the extent of retinopathy, and would be performed as necessary.
The best treatment is prevention as much as possible. Strict glucose control significantly reduces the long-term risk of vision loss. If present, high blood pressure and kidney problems need to be treated. Smoking cessation is crucial.
With proliferative changes, laser intervention in the form of directed or scatter photocoagulation may decrease fluid leakage and lead to regression (resolution) of abnormal vessels. On occasion, the new vessels bleed into the cavity of the eye and surgical evacuation of the blood with microsurgery may be required. Surgery is also the treatment for tractional (tugging) retinal detachments. If the macula is distorted and “out of shape” the visual outcome is worsened by the duration of the alteration.
Vision loss is largely preventable with current methods of diagnosis and treatment. Early detection is vitally important. You can significantly reduce the risk of vision loss with tight blood sugar control, healthy lifestyle implementation, and regular evaluations by your eye care professional.
When first diagnosed with diabetes, an eye exam should occur within five years if you are under 30 years of age; within a few months if older than 30. Pregnant women should be evaluated in the first trimester as retinopathy can progress rapidly during pregnancy. Large fluctuations in blood sugar may also affect refraction (need for glasses) and the strength of the glasses required.
The American Academy of Ophthalmology recommends that adult onset diabetics have annual dilated eye evaluations.
Being knowledgeable about this condition is essential for good care and long-term health.
Dr. McGinn is an ophthalmologist on the Brattleboro Memorial Hospital medical staff.