Diabetic Eye Disease and Retinopathy

Diabetes can cause retinal eye disease. Diabetes is a systemic disease which can affect many different parts of the body over its course, and with medical therapy today, an affected patient can have the disease and survive for many years. In fact, 10 to 15 years may pass before any physical effects of the disease appear. This is particularly true with the eyes, where findings are often first observed late in the disease process. These changes are initially found in the eye because diabetes affects the small blood vessels, which are readily visualized and studied within the eye.

What are the Diabetic Changes Seen in the Eye?

Early in the course of diabetic retinopathy, the findings within the eye can be relatively mild and are referred to as “background diabetic retinopathy” (BDR). The common findings are small dot hemorrhages or micro-aneurysms, small or large blot intra-retinal hemorrhages, yellow deposits (hard exudates), dilated capillaries (IRMA: intraretinal microvascular abnormalities), and white patches (cotton wool spots). BDR generally does not initially affect the center of vision (macula). Therefore, there is no significant loss of vision, and because of this, a diabetic may be asymptomatic for years without knowing that major changes are occurring within the eye. As BDR becomes more advanced, the macula becomes involved and vision starts to deteriorate. 

As conditions worsen, the diabetic changes become more numerous. The dilated capillaries become much more prominent and/or actually close down. The cotton wools spots and hemorrhages are more numerous, and there are large areas in the retina where blood flow is compromised. This phase is called “pre-proliferative diabetic retinopathy or non-proliferative diabetic retinopathy (NPDR)” At this stage, treatment should be started to prevent the next stage, “proliferative diabetic retinopathy” (PDR).

Proliferative diabetic retinopathy is the most severe form of diabetic eye disease. It is divided into several levels, mild, moderate and severe. With the onset of PDR, there is the growth of new, but abnormal, blood vessels in the eye. If this is allowed to progress, these vessels result in major bleeding in the eye, and as these vessels scar down, they pull on the retina, creating traction detachments of the retina. The hemorrhaging and/or the traction detachment of retina, as it involves the center of vision, result in loss of vision.

An OCT and/or a fluorescein angiogram are often useful diagnostic tests.

How Does Diabetes Affect the Eye?

Diabetes affects the eye by changing the normal metabolic pathway of the cells within the eye. In the retina, the cells most sensitive to this change are the cells which support the walls of the blood vessels. As these cells are lost, the integrity of the blood vessels is compromised. The very small blood vessels (capillaries) begin to leak and focally swell, resulting in the leakage of blood into the retina and micro-aneurysms formation. This, in turn, results in swelling of the retina (edema) and intra-retinal hemorrhages. Over time, the capillaries shout down preventing oxygen and nutrients from getting to the retinal tissue. The result of this stress to the retina tissue is the production of a substance which stimulates the formation of the new, but abnormal, blood vessels (neovascularization). These vessels do not have the integrity of normal retinal blood vessels, nor do they stay within the retina. These vessels grow out from the retina into the center of the eye, onto the surface of the vitreous, the jelly-like material which fills the central cavity of the eye. These vessels are initially very delicate and prone to break, which leads to intraocular hemorrhaging. Also, as these vessels continue to grow and mature, some will begin to contract. If there is significant contraction, the retina is pulled away from the wall of the eye creating a traction retinal detachment, and when the macula (the center of the eye responsible for good vision) becomes involved, there is a loss of central vision.

In very severe cases, where there is unchecked stimulation of new blood vessel growth, these vessels will appear on the iris, the color part of the eye. This condition is call “rubeous iridis”, and if not treated early in its course, will result in extreme pressure elevation in the eye, “neovascular glaucoma”. This leads to, not only further loss of vision, but significant eye pain.

What is the Treatment for Diabetic Retinopathy?

The most important “treatment” for diabetic retinopathy is prevention. This means good control of ones blood sugar level at all times, because it is during those periods when the blood sugar level is elevate, that metabolic changes occur within the cells, leading to cell damage. These metabolic changes can be reversed with the return of normal sugar levels, but the damage is not. The accumulation of damage to the cells results in to the diabetic changes discussed above.

Once the more severe diabetic changes appear, laser therapy has been the treatment of choice. Macular involvement is treated with focally application of laser to the micro-aneurysms, and in a more scattered (grid) fashion around the macular in the areas of swelling (edema). More recently, the use of a drug which inhibits neovascular growth factor (anti-VEGF), with or in combination with laser has been shown to be effective in treating diabetic macular edema. Proliferative diabetic retinopathy is treated with more extensive scatter laser either in the area of compromised blood circulation or more commonly, throughout the peripheral retina. This treatment is best performed before there is significant neovascularization because it causes regression and contraction of the new vessels, which can scar down, causing traction on the retina. Occasionally, due to the presence of blood within the eye, cataract, and/or inadequate dilation of the pupil, freezing of the peripheral retina (cryotherapy) is performed in addition to the laser.

Rubeous iridis is best treated early before it leads to glaucoma. Initial treatment is a with anti-VEGF injection followed with either laser and/or cryotherapy, depending upon how well the interior of the eye can be visualized. If the rubeous iridis is severe, therapy may not be successful in preventing the development of high intraocular pressure, and in these cases, glaucoma surgery is necessary.

In extreme cases of diabetic retinopathy, where there is massive hemorrhaging and/or tractional retinal detachment, a vitrectomy is necessary. This is a surgical procedure, performed in the operating room, where the eye is physically entered. Once inside the eye, the blood is removed and the scar tissue, causing retinal traction, is dissected off the retina, followed by pan-retinal laser therapy.

Who Treats Diabetic Eye Disease/Retinopathy?

Diabetic retinopathy is best evaluated and treated by an ophthalmologist who sub-specializes in diseases and surgery of the vitreous and retina. They are generally referred as “retinal specialists”. You can locate one by asking your general ophthalmologist for a referral or searching one out on the internet or in your local telephone directory.