Retinopathy literally means "disease of the retina". Diabetic retinopathy is damage to the retina caused by diabetes, specifically diabetes mellitus.
The retina requires high levels of oxygen to function normally. Longstanding elevated blood sugar results in damage to capillaries, the small blood vessels that transfer oxygen to tissues.
Diabetic damage results in multiple out-pouchings of capillaries called microaneurysms. Microaneurysms allow leakage of blood serum or plasma (the fluid portion of blood) into the retinal layers. This results in swelling (edema) of the retina as well as formation of protein deposits ("hard" exudates) between retinal layers. Macular edema is the most common cause of central vision loss in diabetic retinopathy. There are factors in addition to chronic diabetes which can worsen macular edema. Patients with higher levels of low-density lipids (LDL), or "bad" cholesterol, have twice the risk of developing visual loss from macular edema.
Disruption of blood flow and poor oxygen delivery is termed ischemia. Retinal ischemia may stimulate the formation of new abnormal blood vessels. This process of neovascularization leads to what is called to Proliferative Diabetic Retinopathy (PDR). Prior to this stage the retinal changes are classified as Non-Proliferative (NPDR). Patients with PDR may experience vision loss secondary to retinal malfunction from the underlying ischemia. They may also develop bleeding inside the eye termed vitreous hemorrhage. Neovascularization may adhere to vitreous and result in a form of retinal detachment known as Traction Retinal Detachment (TRD). If retinal ischemia goes untreated it may eventually generate neovascularization on the iris (colored part of the eye around the pupil) causing a severe form of glaucoma known as Neovascular Glaucoma. Many eyes reaching this stage will not have a good visual outcome although aggressive treatment may save the eye.
How do I know if I have Diabetic Retinopathy?
Regular dilated eye examinations are the only certain way to know if you have retinopathy. Timely diagnosis of retinopathy is also the best way to insure effective treatment to minimize vision loss. Ancillary tests such as fluorescein angiography and scanning laser imaging of the retina may be helpful in assessing various aspects of this disease.
Periodic follow-up examinations are necessary to track the progression of retinopathy and the effectiveness of any treatment. Self-monitoring by the patient based on his/her symptoms is not an effective way to assess changes. Symptoms of concern should be reported to your eye doctor without undue delay.
Diabetic visual loss and blindness is an unfortunate event. This can usually be prevented by better management of underlying disease, accurate periodic eye examinations, and timely treatment.
How is Diabetic Retinopathy diagnosed?
Diabetic retinopathy is best diagnosed with a dilated eye exam and, when indicated, special testing. Your eye doctor will place drops in your eyes that make your pupils relax.
Fluorescein Angiography (FA). A safe dye called sodium fluorescein is injected into a hand or arm vein. Timed photos are taken with digital cameras as the dye passes through retinal blood vessels. Patterns of dye leakage and blocking are interpreted by a retinologist to aid in diagnosis.
Optical Coherence Tomography (OCT). This imaging test provides cross-sectional views of the retina that show thickness variations and any fluid features. Subsequent OCT data can be used to trend treatment response.
How is Diabetic Retinopathy treated?
Treatment for diabetic retinopathy is often very effective in preventing, delaying, or reducing vision loss. It is important to remember that diabetes is manageable but not curable. People who have been treated for diabetic retinopathy need to be monitored frequently by an eye doctor to check for new pathology. Many people with diabetic retinopathy need to be treated more than once as their condition worsens.
Laser treatment (photocoagulation) is usually very effective if performed before the retina has been severely damaged. Surgical removal of the vitreous gel (vitrectomy) may be considered for non-clearing vitreous hemorrhage to release internal traction. Injection of VEGF (vascular endothelial growth factor) blocking drugs help shrink blood vessels in proliferative diabetic retinopathy. Corticosteriods are also applied in certain cases.
Tight control of your blood sugar is always important. This is true even if you have been treated for diabetic retinopathy and your eyes are stable. In fact, good blood sugar control is especially important to help keep retinopathy from progressing.
In general, laser treatment should be done relatively early in the course of the disease to prevent serious vision loss rather than to try to treat serious disease after it has already developed.
People with diabetes who have any signs of retinopathy need to be examined and carefully staged by an optometrist or an ophthalmologist well trained in diabetic eye disease.