Diabetes can affect sight. If you have diabetes mellitus, your body does not use and store sugar properly. High blood sugar levels may cause damage to the blood vessels in the retina. The damage to retinal vessels is referred to as diabetic retinopathy.
There are two types of diabetic retinopathy: nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR). NPDR is an early stage of diabetic retinopathy. In this stage, tiny blood vessels within the retina leak blood or fluid. Mild NPDR usually does not affect vision. When vision is affected, it is the result of macular edema or macular ischemia.
Macular edema is swelling or thickening of the macula, a small area in the center of the retina. The swelling is caused by fluid leaking from retinal blood vessels. This is the most common cause of vision loss in diabetes.
Macular Ischemia occurs when small blood vessels close. Vision blurs because the macula no longer receives enough blood supply to work properly.
PDR is present when abnormal new vessels begin to grow on the surface of the retina or optic nerve. The main cause of PDR is 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 closed. The new vessels do not resupply the retina with normal blood flow, and are often accompanied by scar tissue that may cause wrinkling or detachment of the retina. PDR may cause more severe vision loss than NPDR because it can affect central as well as peripheral vision.
PDR causes vision loss in the following ways: Vitreous hemorrhage: The fragile new vessels may bleed into the vitreous, a clear gel-like substance that fills the center of the eye. If the hemorrhage is small, a person may see only a few floaters. A large hemorrhage might block out all the vision. Depending on the amount of blood present, it may take days or even months to reabsorb the blood. If the eye does not clear the vitreous blood adequately within a reasonable time, vitrectomy surgery may be recommended.
Traction retinal detachment: When PDR is present, scar tissue associated with neovascularization can shrink, pulling the retina from its normal position. This can cause visual distortion. Severe vision loss can occur if the macula or large areas of the retina are detached.
Neovascular glaucoma: Occasionally, extensive retinal vessel closure will cause new abnormal vessels to grow on the iris 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.
How is diabetic retinopathy diagnosed? A medical eye examination is the best way to detect changes inside your eye. Ophthalmology Associates has the most up to date diagnostic equipment to aid in the diagnosis of diabetic retinopathy. If diabetic retinopathy is found on examination, colored photographs of the retina, or a special test called fluorescein angiography may be ordered to find out if you need treatment.
How is diabetic retinopathy treated? The best treatment to prevent retinopathy is strict control of your blood sugar. In certain cases it may be indicated to treat your macular edema with injections of medicine in your eye. These shots of medicine – called intravitreal injections – may be steroids or other medications. They are designed to shrink the swelling of the macula or reduce neovascularization.
Laser surgery: Laser surgery is often recommended for people with macular edema, PDR and neovascular glaucoma. For macular edema, the laser is focused on the damaged retina near the macula to decrease the fluid leakage. For PDR, the laser is focused on all parts of the retina except the macula. This panretinal photocoagulation treatment causes abnormal new vessels to shrink and often prevents them from growing in the future. It also decreases the chance that vitreous bleeding or retinal distortion will occur. Multiple treatments over time are sometimes necessary.
Vitrectomy: In advanced PDR, vitrectomy surgery may be recommended. During this microsurgical procedure, which is performed in the operating room, the blood-filled vitreous is removed and replaced with a clear solution. This procedure often prevents further bleeding by removing abnormal vessels that caused the bleeding. If the retina is detached, it can be repaired during the vitrectomy surgery.