Diabetic eye disease is the number one cause of blindness in working-age Americans. In the early stages, diabetic eye disease has no obvious symptoms. If you have diabetes mellitus, high blood-sugar levels can damage blood vessels in the retina, the layer of light sensitive cells at the back of the eye. The damage to retinal vessels is called diabetic retinopathy.
Diabetic Retinopathy Overview
Types of Diabetic Retinopathy
There are two types of diabetic retinopathy: Non-Proliferative Diabetic Retinopathy (NPDR) and Proliferative Diabetic Retinopathy (PDR).
Non-Proliferative Diabetic Retinopathy (NPDR)
In this stage, vision may initially be unaffected. Later, tiny blood vessels within the retina can begin to leak blood or fluid. The leaking fluid causes the retina to swell (macular edema) or to form deposits called exudates. If this occurs in the center of the retina, it will blur your vision. When vision is affected it is usually the result of macular edema. Other times it can be due to the closing off of the blood vessels in the retina (macular ischemia). Vision blurs because the macula no longer receives sufficient blood supply to work properly.
Proliferative Diabetic Retinopathy (PDR)
PDR is present when abnormal new vessels begin growing on the surface of the retina, the optic nerve or the iris. The main cause of PDR is widespread closure of retinal blood vessels, preventing adequate blood flow. The eye responds by growing new blood vessels. Unfortunately, the new, abnormal blood vessels are not functional. The new vessels can bleed and are often accompanied by scar tissue that may cause wrinkling or detachment of the retina. PDR may cause severe vision loss in the following ways:
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. It may take days, months or even years to resorb the blood, depending on the amount of blood present. If the eye does not clear the vitreous blood adequately within a reasonable time, vitrectomy surgery may be recommended. Vitreous hemorrhage alone does not cause permanent vision loss. When the blood clears, visual acuity may return to its former level as long as other structures in the eye are stable.
Traction Retinal Detachment
When PDR is present, scar tissue associated with neovascularization can shrink, wrinkle and pull 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.
Occasionally, extensive retinal vessel closures 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 and severe vision loss and pain.
Visit the American Academy of Opthalmology’s webpage on Diabetic Retinopathy.