In diabetes the body does not use and store sugar properly. High blood sugar levels can damage blood vessels in the retina, the nerve layer at the back of the eye that senses light and helps to send images to the brain. 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 for fluid. The leaking fluid causes the retina to swell or to form deposits called exudates.
Many people with diabetes have mild NPDR, which usually does not affect their vision. When vision is affected it is the result of macular edema and/or macular ischemia.
Macular edema is swelling, or thickening, of the macula, 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 retinal blood vessels. It is the most common cause of visual loss in diabetes. Vision loss may be mild to severe, but even in the worst cases, peripheral vision continues to function.
Macular ischemia occurs when small blood vessels (capillaries) close. Vision blurs because the macula no longer receives sufficient blood supply to work properly.
PDR is present when abnormal new vessels (neovascularization) begin growing 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.
Unfortunately, the new, abnormal blood vessels do not resupply the retina with normal blood flow. The new vessels are often accompanied by scar tissue that may cause wrinkling or detachment of the retina. Macular wrinkling can cause visual distortion. More severe vision loss can occur if the macula or large areas of retina are detached.
The fragile new vessels may bleed into the vitreous, a clear, jelly-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.
Vitreous hemorrhage alone does not cause permanent vision loss. Sometimes the eye will reabsorb the blood on its own over a few weeks and vision will improve. If the eye does not clear the vitreous blood adequately within a reasonable time, 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. Vitrectomy often prevents further bleeding by removing the abnormal vessels that caused the bleeding. If the retina is detached, it can be repaired during the vitrectomy surgery.
Occasionally, extensive retinal vessel closure will cause new, abnormal blood vessels to grow on the iris (colored part of the eye) and 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.
A medical eye examination is the only way to find changes inside your eye. An ophthalmologist can often diagnose and treat serious retinopathy before you are aware of any vision problems.
An office procedure called fluorescein angiography is used to detect hemorrhaging vessels. In the diagnostic test, the blood vessels are imaged by injecting a fluorescent dye into the vein of the arm and tracing its progression through the retinal blood vessels.
An OCT (scan showing topography of the retina) of the retinal layers is used to determine the amount of swelling.
The best treatment is to prevent the development of retinopathy as much as possible. Strict control of blood sugar will significantly reduce the longterm risk of vision loss from diabetic retinopathy. If high blood pressure and kidney problems are present, they need to be treated.
A combination of laser and/or injections into the eye is often recommended for macular edema or swelling. The laser is focused on the damaged retina near the macula to decrease the fluid leakage. The main goal of treatment is to prevent further loss of vision.
For PDR, the laser if focused on all parts of the retina except the macula. This PRP (panretinal photocoagulation) laser treatment causes abnormal new vessels to shrink and often prevent them from growing in the future. It also decreases the chance that vitreous bleeding or retinal distortion will occur. The goal of PRP laser is to decrease the risk of severe vision loss.
Multiple laser treatments over time are sometimes necessary. Laser treatment does not cure diabetic retinopathy and does not always prevent further loss of vision.
Vision loss is largely preventable. With improved methods of diagnosis and treatment, only a small percentage of people who develop retinopathy have serious vision problems. Early detection of diabetic retinopathy is the best protection against loss of vision.
Maintaining strict control of blood sugar and regular eye exams can significantly lower your risk of vision loss.
People with diabetes should schedule examinations at least once a year. More frequent medical eye examinations may be necessary after the diagnosis of diabetic retinopathy.
You should have your eyes checked promptly if you have visual changes that affect only one eye, last more than a few days, and that are not associated with a change in blood sugar.
When you are first diagnosed with diabetes, you should have your eyes checked within five years of the diagnosis if you are 30 years old or younger and within a few months of the diagnosis if you are older than 30 years.