Diabetes mellitus is a condition that can have an effect on the small blood vessels of the body. One location of such small blood vessels is the **retina in the eye. When the retinal blood vessels are affected, this is a condition called diabetic retinopathy.
Diabetic retinopathy increases with the duration of the diabetes. It is unusual to see clinical signs of diabetic retinopathy prior to ten years after the onset of the disease. Diabetic retinopathy can progress with time and has become the leading cause of legal blindness in working-aged adults. Treatment of diabetic retinopathy has improved over the last several years and blindness due to diabetes is becoming less frequent. In addition to treatment of the retina directly, recent studies have shown that strict blood sugar control can delay the onset and progression of diabetic retinopathy.
Clinically, diabetic retinopathy is divided into two broad categories, non-proliferative and proliferative retinopathy.
Non-proliferative Retinopathy is caused by damage to the walls of normal retinal blood vessels. The damage to the walls of the vessels results in leakage of blood and fluid from the small blood vessels. This results in swelling of the retina, like a sponge taking up water. If the swelling involves the **macula (center of the vision), then the vision is affected. Fatty material (lipid) can leak from blood vessels and can result in more permanent loss of vision. More severe damage to the retinal blood vessels can result in closure of vessels and decreased blood flow to areas of the **retina. If this loss of blood flow and nutrition involves the center of the vision, significant loss of vision can result.
Proliferative Retinopathy results when there is the development of abnormal ("neovascular") blood vessels in addition to the normally present retinal blood vessels. Blockage of small blood vessels result in decreased blood flow to large areas of the retina. The retina becomes "starved" for oxygen and a chemical signal is sent from the damaged retina to induce the body to grow new blood vessels. This is the body's response to provide more oxygen to those areas, but the new blood vessels are fragile and grow from the surface of the **retina into the **vitreous "jelly" in the center of the eye. The movement of the vitreous "jelly" can result in rupture of the fragile vessels, resulting in bleeding into the center of the eye. With time, the abnormal blood vessels can scar over, contract and pull on the surface of the retina. This pulling can cause the retina to come away from the back of the eye (**retinal detachment) and can result in permanent blindness.
Treatment of diabetic retinopathy consists of in-office laser photocoagulation and/or a surgical procedure known as ** vitrectomy.
Laser photocoagulation can be used to achieve one of two goals. Laser can either cauterize blood vessels that are leaking to stop leakage or it can destroy damaged retinal tissue by creating scarring.
In non-proliferative diabetic retinopathy, vision loss can be caused by leakage from retinal blood vessels. Laser is applied to the areas of leakage to try to decrease leakage and allow the body to reabsorb leaked material. The laser is often guided by a photograph test known as fluorescein angiography. This test is performed in the office by injecting an intravenous fluorescein dye while photos are taken of the dye circulation through the retina. The risk of significant visual loss can be reduced by the use of laser in non-proliferative diabetic retinopathy.
In proliferative diabetic retinopathy, new, abnormal, blood vessel growth develops due to chemical signals sent out by the damaged retina. In this situation, laser is applied to try and ablate damaged retina by creating scarring. If the damaged retina is destroyed, new blood vessel growth will regress. This ablation of damaged retina requires the application of many (often more than 1000) laser burns to the peripheral retina. This may be done in one or multiple sessions and can be done with or without anesthetic injection around the eye.
Significant visual loss can be reduced by up to 66% with the use of laser treatment in proliferative diabetic retinopathy. There can be side effects of this more intense laser treatment, such as decreased night vision, decreased peripheral vision and blurring of central vision.
The need for vitrectomy surgery is indicated when there is bleeding into the center of the eye that persists and cannot be treated with laser. At times, scar tissue formation from abnormal blood vessel growth can cause pulling on the retina and retinal detachment. Vitrectomy surgery is a microscopic surgery with small instrumentation that is used to remove vitreous, blood and certain scar tissue. Damage that results in the need for vitrectomy surgery is often advanced. The goals of surgery are to regain ambulating vision and occasionally reading vision.
In summary, vision can often be maintained in diabetes. Strict blood sugar control and regular examinations for early detection are critical elements in maintaining as much vision as possible. The incidence of diabetic retinopathy goes up after 10 years of diabetes. The frequency of examination will be determined by your eye specialist. Very close monitoring of diabetic retinopathy is necessary during pregnancy, as progression can occur. If changes of diabetic retinopathy threaten visual loss, laser photocoagulation should be considered. We often can maintain vision at a certain level, but regaining vision lost is often not possible.