NPDR, commonly known as background retinopathy, is an early stage of diabetic retinopathy. In this stage, tiny blood vessels within the retina leak blood or fluid. The leaking fluid causes the retina to swell or form deposits called exudates.
Many people with diabetes have mild NPDR, which usually does not affect their vision. When vision is affected, it is because of macular edema (pronounced “eh-DEEM-uh”), macular ischemia (pronounced “ih-SKEE-me-uh”), or both.
Macular edema is the swelling or thickening of the macula, which is a small area in the center of the retina that allows us to see fine details clearly. The swelling is caused by fluid leaking from the retinal blood vessels. It is the most common cause of visual loss in diabetes.
Macular ischemia occurs when small blood vessels (capillaries) close. Vision blurs when the macula does not receive sufficient blood supply to function. PDR is present when abnormal new vessels begin growing (neovascularization) on the surface of the retina or optic nerve. The main cause of PDR is the widespread closure of retinal blood vessels, preventing adequate blood flow. The retina responds by growing new blood vessels in an attempt to supply blood to the area where the original vessels have closed.
PDR causes visual loss in the following ways:
Vitreous hemorrhage. The fragile new vessels may bleed pouring their contents into the vitreous, which is the clear gel-like substance that fills the center of the eye. If the vitreous hemorrhage is small, a person might see only a few new dark floaters. A very large hemorrhage might block out all vision. It may take days, months, or even years to reabsorb the blood, depending on the amount of blood present. If the eye does not clear the vitreous blood adequately within a reasonable time, vitrectomy may be recommended.
Traction retinal detachment. When PDR is present, scar tissue associated with the neovascularization can shrink, causing the retina to wrinkle and pull away from its normal position. Macular wrinkling can cause visual distortion. More severe vision loss can occur if the macula or large areas of the retina are detached.
Neovascular glaucoma. Occasionally, extensive retinal vessel closure causes new, abnormal blood vessels to grow on the iris (colored part of the eye) and in the drainage channels in the front of the eye. This can block the normal flow of fluid out of the eye. Pressure in the eye builds up, resulting in neovascular glaucoma, a severe eye disease that causes damage to the optic nerve.
Unfortunately, the new abnormal blood vessels do not supply the retina with normal blood flow. The new vessels are often accompanied by scar tissue that may cause wrinkling or detachment of the retina. PDR may cause more severe vision loss than NDPR because it can affect both central and peripheral vision.
How is diabetic retinopathy diagnosed?
A medical eye examination is the best way to detect changes inside the eye. An ophthalmologist (eye M.D.) can often diagnose and treat serious retinopathy before you are aware of any vision problems. The ophthalmologist dilates your pupil and looks inside the eye with the help of special equipment and lenses. If your ophthalmologist diagnoses diabetic retinopathy, he/she may order color photographs of the retina or a special test called fluorescein angiography to determine whether you need treatment. In this fluorescein test, a dye is injected into your arm and photos of your eye are taken to detect where the fluid is leaking.
How is diabetic retinopathy treated?
The best treatment is to prevent the development of retinopathy as much as possible. Strict control of blood sugar will significantly reduce the long-term risk of vision loss in diabetic retinopathy. If high blood pressure and similar problems are present, they need to be treated.