What You Should Know About Diabetic Retinopathy

What is diabetes?
Diabetes mellitus is a disease causing the blood sugar (glucose) to become elevated. There are two basic kinds of diabetes. Type 1 diabetes is diagnosed early in life and requires insulin to bring the glucose level down to normal. Type 2 diabetes occurs later in life, and can be controlled with diet, pills, or insulin, depending on its severity. Approximately 18 million Americans have diabetes, with over one-third of those affected being undiagnosed.

How does diabetes affect the eye?
Diabetes primarily affects the blood vessels that nourish the retina. The retinal vessels work like a garden hose, bringing oxygen and other nutrients into and out of the eye. Diabetes causes them to sprout tiny leaks, or microaneurysms (background diabetic retinopathy), which makes the surrounding retina swell and not work properly. Central vision can become blurred, just as a water droplet placed on a photograph will cause the picture to blister and become distorted (diabetic macular edema).

OCT scan (top) of normal macula compared to OCT image of diabetic macular edema (bottom).

Diabetes can also make the blood vessels close off. Some eyes will develop tiny new blood vessels in an attempt to increase the retinal blood supply (proliferative diabetic retinopathy).  These new vessels do not help the eye, however. They are fragile and can cause blindness by hemorrhaging or retinal detachment.

Who gets diabetic retinopathy?
Diabetic retinopathy develops gradually over many years. People with Type I diabetes, those requiring insulin to control their blood sugar, and patients with diabetes for many years are at an increased risk for developing retinal problems. Poor control of the blood glucose, pregnancy, uncontrolled high blood pressure, and smoking also aggravate diabetic retinopathy.

Approximately 50% of diabetics (about 5 million Americans) will develop some form of diabetic retinopathy. Diabetic retinopathy is the leading cause of vision loss and new-onset blindnesss in the United States in those 20 to 74 years of age, with new cases of blindness developing in 12,000 to 24,000 persons annually. Remarkably, much of this vision loss is preventable with more timely diagnosis and treatment.

How is diabetic retinopathy diagnosed?
You can't diagnose diabetic retinopathy by looking in the mirror since your eye will usually look and feel normal. Vision is also often normal despite the presence of potentially blinding eye conditions. Only a thorough retinal examination through a dilated pupil can detect these problems. Properly timed laser treatment can effectively stabilize vision although it is less likely to improve it. The key to maintaining good eyesight, therefore, is early diagnosis and treatment before symptoms occur. Most diabetic patients need dilated eye examinations at least once a year throughout their lifetime. Further testing, including photography and fluorescein angiography, may be done to assist in the diagnosis and treatment of any changes thought to cause visual loss.

Normal Vision.		Diabetic Retinopathy.

What treatments are available for diabetic retinopathy?

1) Medical.
Good control of your blood sugar can significantly decrease the chances of diabetic retinopathy developing or progressing. However, there are some people who, despite eating right and controlling their diabetes as best as possible, will still get significant eye disease.

2) Laser surgery.



a) Introduction. 
Laser photocoagulation is one of the main ways that diabetic retinopathy is treated. A laser is an instrument that produces a pure, high-intensity beam of light energy. The laser light can be focused onto the retina, selectively treating the desired area while leaving the surrounding tissues untouched. The absorbed energy heats, or photocoagulates, the retina, creating a microscopic spot.

Laser surgery is performed in our office while you are awake and comfortable. The laser treatment usually takes less than 30 minutes to complete and you can go home immediately following surgery. Arrangements for transportation should be made in advance since you may not be able to drive right away.

It will take several weeks to months before we can tell whether the laser surgery has been successful. Since diabetes is a progressive disease, many patients need more than one treatment to control their eye problem and prevent further loss of vision.

b) Macular edema. 
The laser is used to seal the leaking vessels causing macular edema (focal or grid photocoagulation).  In the Early Treatment Diabetic Retinopathy Study, photocoagulation decreased the risks of persistent macular edema and significant visual loss by about 50%, regardless of the baseline vision.  Significant visual loss occurred in 5% of treated eyes compared to 8% of untreated eyes at 1 year, 7% of treated eyes compared to 16% of untreated eyes at 2 years, and 12% of treated eyes compared to 24% of untreated eyes at 3 years of follow-up.  Photocoagulation was shown not to be of benefit for eyes without clinically significant macular edema, as the risk of significant visual loss with or without treatment was small.  Photocoagulation did not significantly improve vision.
 

Central diabetic macular edema with yellow, fatty lipid threatening the macular center.		Excellent response following laser photocoagulation.

c) Proliferative diabetic retinopathy. 
New vessels in eyes with proliferative retinopathy can often be made to disappear with panretinal photocoagulation.  Microscopic laser spots, placed into the peripheral retina, improve retinal circulation causing neovascularization to disappear.

Panretinal photocoagulation consists of yellow laser spots placed outside the optic nerve and macula.

In the Diabetic Retinopathy Study, the overall risk of severe visual loss with proliferative diabetic retinopathy at the 2-year follow-up examination was 16% in the control eyes compared to 6% in the treated eyes.  With Diabetic Retinopathy Study high-risk characteristics, this risk increased to 26% of the control eyes and 11% of the treated eyes.
 

Lacy new blood vessels (disc neovascularization) are seen (arrow) overlying the optic nerve.		The new vessels resolved following panretinal photocoagulation.

3) Intraocular steroids.
Although laser photocoagulation was the only treatment available for diabetic macular edema since the 1970's, the recent advent of intraocular steroids has added another successful treatment for this disease. Injection of anti-inflammatory steroid medication (Kenalog) into the eye (a painless in-office procedure) appears to rapidly improve macular edema and vision loss, often more successfully than laser. However, the injections often have to be repeated every 4-6 months, and the long-term visual results remain to be determined. Temporarily increased eye pressure (glaucoma) and cataract are the most common and treatable side-effects. Pending ongoing studies, the role of laser photocoagulation versus intraocular steroids is still unclear. Studies are also ongoing evaluating devices that will allow for a long-term, sustained release of steroids into the eye. Your doctor will discuss which treatment, if any, he feels would be best for your eye.

4) Vitrectomy surgery.
Some patients with severe proliferative retinopathy will develop extensive bleeding or retinal detachment that can cause blindness. Vitrectomy surgery is done at the hospital, usually on an outpatient basis. These advanced microsurgical techniques often allow us to restore vision by removing the hemorrhage and bleeding tissues. Vitrectomy is also used for some eyes with macular edema that fail to respond to laser photocoagulation or intraocular steroids.

Yellowish neovascular tissue is detaching the macula.		The retina reattached following vitrectomy surgery.