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What is Diabetic Retinopathy?

Diabetic retinopathy is a complication of diabetes which affects the small blood vessels in the retina. These changes can cause mild to severe loss of vision. In fact, diabetes is the leading cause of severe visual loss in Americans between the ages of 20 and 64. None-the-less, with careful diabetic management and timely laser surgery by a retina laser specialist, good vision can usually be maintained.
Fortunately, in the recent past, major advances have occurred in the treatment of diabetic retinopathy and today we are often able to halt the progression of visual loss. With careful diabetic management and timely laser surgery by a laser specialist, good vision can usually be maintained.

Read about Proliferative Diabetic Retinopathy

How the Eye Works

The retina is a thin layer of nerve tissue that lines the back of the eye. It receives light signals coming in from the front of the eye and sends them on to the brain so that vision can occur. A small, specialized area of the retina called the macula is responsible for all the fine visual tasks. The rest of the retina provides peripheral and night vision. Directly in front of the retina is the vitreous gel. This gel fills the inside of the eye.
The nourishment for the retina comes from a network of arteries, veins and capillaries which is called the retinal circulation.

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Background diabetic retinopathy

These blood vessels may be damaged by diabetes reducing the nourishment to the retina. Diabetes usually is present a number of years before any detectable damage takes place and the effects are quite variable from patient to patient. Some diabetics show few signs of problems in the eyes, even after 25 or more years of diabetes, while others have many changes in the retina after a relatively short period of time. Often there are serious changes occurring before a diabetic patient notes any visual loss. This is the reason frequent examinations of the back of the eye (retina) by an eye specialist are necessary to detect diabetic changes before they affect the vision.

The retinal complications of diabetes are divided into two types:
Background Diabetic Retinopathy or Non-Proliferative Retinopathy (leaking blood vessels) and Proliferative Diabetic Retinopathy (new blood vessels).

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Ninety percent of patients with diabetic retinopathy have background diabetic retinopathy which is usually the milder form of diabetic eye problems. In this condition the tiny retinal blood vessels hemorrhage and develop leaks especially in the central retina (macula). This causes an abnormal leakage of serum and fatty materials which can accumulate resulting in retinal swelling or macular edema. This edema causes blurred vision which is especially noted in reading or doing close work. The amount of leakage varies and can cause a decrease in vision ranging from minimal to as bad as legal blindness (20/200). There is, however, no pain, redness or sudden loss of vision. Only when this fluid enters the center vision area, or macula, will the decreased vision be noted. Treatment should be instituted before this happens if at all possible.

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Fluorescein Angiography

Diagnosis of background diabetic retinopathy is made during a complete eye exam when the pupil is dilated and is aided by a test called fluorescein angiography. In this test a special vegetable dye is injected into a vein in the patient's hand or arm. The dye is carried by the bloodstream to the retina and a rapid sequence of pictures is taken. The small vessels damaged by diabetes leak the fluorescein dye and, in this way, the exact location and extent of abnormal blood vessels can be determined.
This test is not painful and no x-rays are used (after the angiogram patients may notice some temporary yellow discoloration to the skin and urine but this lasts only a short time). This dye is not related to ones you may have had for kidney or intestinal tests.

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Treatment of Background Diabetic Retinopathy with Lasers

The laser is a bright light that can be focused to a very small spot on the retina. When this highly focused beam hits the retina, the tissue heats up and leaking and abnormal blood vessels are cauterized or coagulated. The treatment can be performed in the office or in the outpatient department of the hospital. The laser treatment for retinal edema is not painful but the laser beam must be aimed at a spot the size of a pinhead. The patient is given drops to dilate the pupils and then a local anesthetic is injected behind the eye lid to numb the eye and keep it steady during the laser treatment. The treatment itself only takes 10 or 15 minutes. After treatment the eye is patched for several hours but normal activities can usually be resumed the next day.
When the macular edema is caused by specific leaks in the blood vessels, laser treatment can often effectively seal the individual leaks preventing further loss of vision and, at times, improving the vision as well. In other cases the leakage is diffuse, or generalized, and a laser treatment in the form of a "grid" is applied, again with the intention of stabilizing vision. Unfortunately there are cases when the leakage is so far advanced or the circulation to the macula is so poor that laser treatment will not be successful. These facts are important to realize as sometimes the stabilization or improvement in vision is not what the patient had hoped for. Realistically, in most cases a stabilization of vision is the most that can be hoped for and two or more laser treatments in each eye may be necessary. This is rarely a one-time only treatment.
A nationwide study showed that patients with background diabetic retinopathy who had laser treatment did twice as well as a similar group that did not have treatment. Laser treatment is usually beneficial if it is carried out early and the diabetes is well controlled.

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Proliferative Diabetic Retinopathy

The second, and potentially more serious form of diabetic retinopathy, is called Proliferative Diabetic Retinopathy. In this condition, new, fragile blood vessels develop or "proliferate" on the surface of the retina or from the optic nerve and grow into the vitreous gel. These abnormal blood vessels can break and bleed into the vitreous (vitreous hemorrhage) and over the surface of the retina, blocking out the incoming light and severely decreasing vision.
When the bleeding is minimal the eye can reabsorb the blood and the vision will clear. At other times, however, the blood may not clear or scar tissue may form in the areas of new blood vessels and old blood. As the scar tissue shrinks it may pull the retina forward causing more distortion and visual loss, what is known as a "traction retinal detachment."

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Treatments for Proliferative Diabetic Retinopathy

The treatment of proliferative diabetic retinopathy is a laser technique called "PanRetinal Photocoagulation" (PRP). In this procedure 1,200 to 3,000 separate laser burns are applied to the peripheral retina in an attempt to redirect blood flow to the more important central retinal areas. This tends to curtail further development of new blood vessels and in time usually causes the already present abnormal vessels to regress or disappear. Overall there is a 60% reduction in severe visual loss when treatment is given at the appropriate time. The laser treatment is performed as an outpatient procedure in the hospital or in the office and usually requires 3 treatment sessions per eye, the first two spaced about one week apart and the third, if necessary, 1 to 2 months later. The treatment may cause some loss of side vision and a decrease in night vision but the loss is usually not very noticeable to the patient and is far better than the marked loss of vision caused by a hemorrhage into the vitreous. The major objective is to control the new blood vessels before they hemorrhage to try to prevent scar tissue formation which may cause irreparable damage.

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Intravitreal injections of Anti-VEGF drugs such as Avastin and Lucentis target a specific chemical in your eye called VEGF or vascular endothelial growth factor which are critical in causing abnormal blood vessel growth on the surface of the retina. These Anti-VEGF drugs can help reduce the growth of abnormal blood vessels, which helps prevent bleeding and scar tissue, and other problems that can cause vision loss. The Anti-VEGF drug is administered directly into the eye in an outpatient setting. After dilating drops and an anaesthetic is given to numb the eye, the injection is given. It takes only a few seconds and feels like a tiny scratch. Your vision may be blurry for several hours afterwards due to the dilating drops but should improve by the next day.

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Vitrectomy

When blood in the eye does not clear, or when scar tissue pulls the retina loose, laser is no longer possible or helpful. In these cases a surgical procedure called "vitrectomy" is performed. Working under a microscope and using tiny instruments placed inside the eye, the blood filled vitreous is removed and replaced with a clear saline solution. In addition, scar tissue is cut and removed in an attempt to relieve the pulling on the retina. Laser and other special techniques may be used at the time of surgery. Air or special gases may be used to keep the retina in place until healing takes place. In general, at least 70% of vitrectomy patients notice improvement in vision but in severe cases the prognosis is much more guarded.

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Summary

The best way to prevent visual loss from diabetes is early detection of diabetic retinopathy with appropriate treatment. All diabetic patients should have a complete eye examination at least once a year even if there are no symptoms of visual problems. If diabetic retinopathy is diagnosed, more frequent examinations will be necessary. Good diabetic control is important. This includes daily blood glucose checks and rigid blood pressure control.
Laser therapy and intravitreal injections are safe, effective ways to prevent severe visual loss. They are performed in an outpatient setting in the office or hospital outpatient department. They typically only take minutes to perform including time to dilate and numb the eye. These treatments are excellent in retarding further loss of vision but, in most instances, cannot completely reverse the damage that has already occurred.
There is great hope for preserving sight but it requires the close cooperation of the internist, vision specialist, retinal specialist and the patient. We are specialists dealing only in the diagnosis and treatment of retina and vitreous problems. We are very experienced in these treatments and have a combined experience of over 60 years. Working together we can help preserve your vision.