Diabetic retinopathy is damage to the retina caused by diabetes from abnormally high blood sugar levels. Naturally the level of circulating blood sugar must average 100 mg/dl (80 to 100 fasting and 120 two hours after meals). Long standing higher concentrations of blood sugar results in damage to capillaries (tiny, hair-like blood vessels). Since the retina requires high levels of oxygen to function normally, capillaries are in abundance in the retina.
Early damage results in damage to capillaries and the development of microaneurysms. Microaneurysms initially allow leakage of the blood serum or plasma (the fluid portion of the blood) into the retinal layers resulting in swelling or edema of the retina as well as formation of cholesterol type deposits known as exudates between superficial retinal layers. When this occurs in the macula (the center portion of the retina) this is called macular edema.
Macular edema is the most common cause of central vision loss in diabetic retinopathy. There are also other factors which can worsen macular edema. Recent research has shown that patients with higher levels of low-density lipids (LDL), or “bad” cholesterol, have twice the risk of developing visual loss from macular edema. Also, diabetics taking Avandia (rosiglitazone maleate) for glycemic control have rarely been reported to have new onset or worsening macular edema. Microaneurysms in time may burst causing localized retinal hemorrhages. The presence of microaneurysms, retinal hemorrhages, retinal leakage and exudates is termed Nonproliferative (or Background) Diabetic Retinopathy (NPDR).
Diabetic retinopathy also results in disruption of retinal blood flow and poor retinal oxygen flow, a state know as ischemia. Retinal ischemia usually results in formation of new abnormal blood vessels known as neovascularization. In the presence of retinal neovascularization, the disease is called Proliferative Diabetic Retinopathy (PDR). Patients with PDR may experience vision loss as the result of the underlying ischemia or may develop bleeding inside the eye cavity known as vitreous hemorrhage.
Neovascularization could also form scars on the surface of the retina which may result in a form of retinal detachment known as Traction Retinal Detachment (TRD) which is treated with vitrectomy. If retinal neovascularization goes untreated it could also grow on the iris (colored part of the eye) (Iris Neovascularization) causing a severe form of glaucoma known as Neovascular Glaucoma. Many eyes reaching this stage will not have a good visual outcome, although prompt treatment with Avastin/Lucentis/Eylea injections can save the eye.
Q: How Do I Know If I Have Retinopathy?
A: Regular dilated eye examinations are the only way certain to know if you have retinopathy. Timely diagnosis of retinopathy is also the best way to insure effective treatment to decrease the possibility of vision loss. Other ancillary tests such as fluorescein angiography, which is a diagnostic test using a dye to study retinal vessels, or OCT (optical coherence tomography) which measures retinal thickness, may be helpful in assessment of various aspects of this disease.
Periodic follow-up examinations are also necessary to track the progression of the disease, as well as the effectiveness of any treatment. Self-monitoring by the patient based on his/her vision is not an effective way to assess changes, as the progression of retinopathy does not always result in further vision loss. However, if any worsening of the vision is noted, you should report to your eye doctor immediately.
Q: Are there any treatments for diabetic retinopathy?
A: The primary management of diabetic retinopathy as a preventive strategy is optimum control of the blood sugar, blood pressure and cholesterol.
Both macular edema and neovascularization must be treated with laser and/or intravitreal injections. Although laser is an extremely effective therapy for diabetic retinopathy, monthly intravitreal injections of Lucentis, Avastin, or Eylea have been proven to be even more effective. Early detection and treatment insures better long term prognosis. But even if the diagnosis is made in more advanced stages, effective treatment is often still possible.
In the presence of vitreous hemorrhage, traction retinal detachment, and neovascular glaucoma, most patients have to undergo operating room surgery called vitrectomy and possibly glaucoma surgery.
Diabetic visual loss and blindness is an unfortunate event, however, in the majority of cases this can be prevented by better management of the disease, proper eye examinations, and timely treatment.