If you have diabetes mellitus, your body does not use and store sugar properly. High blood-sugar levels can damage blood vessels in the retina. The damage to the blood vessels is referred to as diabetic retinopathy.
Types of Diabetic Retinopathy
There are two types of diabetic retinopathy: non-proliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR).
NPDR, previously referred to as background retinopathy, is an early stage of diabetic retinopathy. In this stage, small blood vessels within the retina leak blood or 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 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 form retinal blood vessels. It is the most common cause of vision loss in diabetes. Vision loss may be mild to severe, but even in severe cases, peripheral vision may function normally.
Macular Ischemia occurs with small blood vessels (capillaries) close. Vision blurs because the macula no longer receives sufficient blood supply to work properly.
NPDR with Macular Edema
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, but abnormal, blood vessels in an attempt to supply blood to the area where the original blood flow was lost.
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.
PDR may cause more severe vision loss than NPDR because it can affect both central and peripheral vision.
PDR causes vision loss in the following ways:
Vitreous Hemorrhage: The fragile new vessels may bleed into the vitreous (gel like substance that fills the cavity 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 longer to absorb the blood, depending on the amount of blood present. If the eye does not clear the vitreous hemorrhage within a reasonable time, vitrectomy surgery may be recommended.
Vitreous hemorrhage alone does not cause permanent vision loss. When the blood clears, vision may return to it’s previous level, if the macula was not damaged.
PDR with vitreous hemorrhage
Traction Retinal Detachment: When PDR is present scar tissue associated with the new blood vessels can shrink, wrinkling and pulling the retina 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.
PDR with traction retinal detachment
Neovascular Glaucoma: Occasionally, extensive retinal vessel closure will cause new, abnormal blood vessels to grow on the iris (colored portion in the front 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 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. An ophthalmologist can often diagnose and treat serious retinopathy before you are aware of any vision problems.
Photographs, including a dye study test called fluorescein angiography, and scans (OCT), may be performed to determine the extent and potential need for treatment.
How is Diabetic Retinopathy Treated?
The most important treatment is to prevent the development of retinopathy as much as possible. Strict control of blood sugar, blood pressure, and lipid control will significantly reduce the long-term risk of vision loss from diabetic retinopathy.
Medical Treatment: In certain cases, your ophthalmologist may choose to treat your macular edema wit injections of medicine inside the eye. These injections are aimed at reducing the swelling in the center of the retina, or helping to control abnormal blood vessel growth.
Laser Surgery: Laser surgery is often recommended for macular edema, PDR, and neovascular glaucoma.
For macular edema, the laser is focused on the damaged retina near the macula to reduce fluid leakage. The main goal of treatment is to prevent further vision loss. The recovery of normal vision is not common, although some may notice some improvement. Some patients may see the laser spots near the center of the vision following treatment. The spots typically fade with time but may never go away completely.
For PDR, the laser is focused in the peripheral retina, away from the macula. This treatment causes abnormal new vessels to shrink and often prevents them from growing in the future. It also reduces the chance of vitreous hemorrhage.
Multiple laser treatments over time are often necessary. Laser surgery does to cure diabetic retinopathy and does not always prevent further loss of vision.
Vitrectomy Surgery: In advanced PDR, or is some cases of severe macular edema, your ophthalmologist may recommend vitrectomy. 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.
Vision loss from Diabetes is largely preventable!
Today, with improved methods of diagnosis and treatment, a smaller percentage of patients who develop retinopathy have serious vision problems, though vision loss still can occur.
Early detection of retinopathy is the best protection against loss of vision.
You can significantly lower your risk of vision loss by maintaining strict control of you blood sugar and visiting your ophthalmologist regularly.
Click on the following link to the American Academy of Ophthalmology EyeSmart page for more information:
(*the above information was adapted from the handout “Diabetic Retinopathy, A closer Look”, provided by the American Academy of Ophthalmology)