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Treatment of Diabetic Retinopathy
and Macular Edema

By Marilyn Haddrill

Millions of Americans each year face vision loss related to diabetes. In fact, according to recent data from the U.S. Centers for Disease Control and Prevention (CDC), nearly 26 million Americans — roughly 8.3 percent of the U.S. population — have diabetes, and more than 28 percent of diabetics age 40 or older in the U.S. have diabetic retinopathy (DR) and related diabetic eye disease.

To make matters worse, a significant number of cases of diabetes and diabetic eye disease go undetected or untreated because people fail to have routine comprehensive eye exams as recommended by their optometrist or ophthalmologist.

Most laser and non-laser treatments for diabetic eye disease depend on the severity of the eye changes and type of vision problems you have.

Diabetic retinopathy is diabetes-related damage to the tiny blood vessels that supply oxygen and nourishment to the light-sensitive retina in the back of the eye. The resulting poor blood supply causes reduced oxygen supply (hypoxia) and accumulation of fluid (edema) in the retina, eventually causing vision loss.

Research also has shown that the retinas in diabetic patients may produce abnormal amounts of vascular endothelial growth factors (VEGF), which stimulate the production of abnormal blood vessels — a process called neovascularization.

The blood vessels produced by this process are fragile and can easily break open, leaking blood and other blood products such as proteins into the back of the eye, obscuring vision.

Diabetic retinopathy can cause swelling and fluid accumulation in the macula, which is a small area in the central retina that is responsible for our most acute vision. Proper functioning of the macula is essential for tasks such as driving a car, watching TV, working at a computer and reading.

Swelling of the macula from diabetes — called diabetic macular edema (DME) — is the most common cause of vision loss among diabetics and is the leading cause of new cases of blindness in adults 20 to 74 years old in the United States, according to CDC.

Lasers for Diabetic Retinopathy Treatment

Laser treatment of diabetic eye disease generally targets the damaged eye tissue. Some lasers treat leaking blood vessels directly by "spot welding" and sealing the area of leakage (photocoagulation). Other lasers eliminate abnormal blood vessels that form from neovascularization.

Lasers also may be used to intentionally destroy tissue in the periphery of the retina that is not required for functional vision. This is done to improve blood supply to the more essential central portion of the retina to maintain sight.

The peripheral retina is thought to be involved in formation of VEGF responsible for abnormal blood vessel formation. When cells in the peripheral retina are destroyed through panretinal photocoagulation (see below), the amount of VEGF is reduced, along with the potential to produce abnormal retinal blood vessels.

After laser treatment of the peripheral retina, some blood flow bypasses this region and instead provides extra nourishment to the central portion of the retina. The resulting boost of nutrients and oxygen helps maintain the health of cells in the macula that are essential for detailed vision and color perception. However, some peripheral vision could be lost due to this treatment.

The two types of laser treatments commonly used to treat significant diabetic eye disease are:

If you have a diabetic vitreous hemorrhage, you may require a vitrectomy to remove the clear, gel-like substance in your eye's interior.

• Focal or grid laser photocoagulation. This type of laser energy is aimed directly at the affected area or applied in a contained, grid-like pattern to destroy damaged eye tissue and clear away scars that contribute to blind spots and vision loss. This method of laser treatment generally targets specific, individual blood vessels.
• Scatter (panretinal) laser photocoagulation. With this method, about 1,200 to 1,800 tiny spots of laser energy are applied to the periphery of the retina, leaving the central area untouched.

Treatment of clinically significant DME also entails using fluorescein angiography to provide images of the eye's interior. These images accurately guide application of laser energy, which helps "dry up" the localized swelling in the macula. A fluorescein angiogram also can identify the location of blood vessel leakage caused by proliferative diabetic retinopathy.

While laser treatment for diabetic retinopathy usually does not improve vision, the therapy is designed to prevent further vision loss. Even people with 20/20 vision who meet treatment guidelines should be considered for laser therapy to prevent eventual vision loss related to diabetes.

What To Expect Before, During and After Laser Treatment

Laser treatment typically requires no overnight hospital stay, so you will be treated on an outpatient basis in a clinic or in the eye doctor's office.

Make sure you have someone drive you to and from the office or clinic on the day you have the procedure. Also, you'll need to wear sunglasses afterward because your eyes will be temporarily dilated and light sensitive.

During photocoagulation, heat from a high energy laser seals off bleeding in damaged eye tissue.

Before the procedure, you will receive a topical anesthetic or possibly an injection adjacent to the eye to numb it and prevent it from moving during the laser treatment.

Your eye doctor will make these types of adjustments to the laser beam before it is aimed into the eye:

• The amount of energy used
• The size of the "spot" or end of the beam that is directed into the eye
• The pattern applied by the laser beam onto the targeted area

A laser treatment typically lasts at least several minutes, but more time may be required depending on the extent of your eye condition.

During laser treatment, you might experience some discomfort, but you should feel no pain. Right after a treatment, you should be able to resume normal activities. You might have some discomfort and blurry vision for a day or two after each laser treatment.

The number of treatments you need will depend on your eye condition and extent of damage. People with clinically significant diabetic macular edema may require three to four different laser sessions at two- to four-month intervals to stop the macular swelling.

Though the specific mechanism by which laser photocoagulation reduces diabetic macular edema is not fully understood, a landmark study called the Early Treatment Diabetic Retinopathy Study (ETDRS) showed that focal (direct/grid) photocoagulation reduces moderate vision loss caused by DME by 50 percent or more.

In December 2011, Iridex Corporation announced the results of a 10-year study of the company's MicroPulse laser therapy for treating DME. The study data showed the new micropulse technology was at least as effective as conventional laser photocoagulation in the treatment of macular edema, with less risk of thermal damage and scarring to the surrounding retinal tissue.

If you have proliferative diabetic retinopathy (PDR) — meaning that leakage of fluid has begun in the retina — the laser treatment should take from 30 to 45 minutes per session, and you may require up to three or four sessions.

Your chance of preserving your remaining vision when you have PDR improves if you receive scatter laser photocoagulation as soon as possible following diagnosis.

Early treatment of PDR particularly is effective when macular edema also is present.

Non-Laser Treatment of Diabetic Macular Edema

Injection of steroids into the eye — either directly or in the form of an injectable implant — often is recommended over laser procedures for the treatment of diabetic macular edema. Or, in some cases, a combination of steroid injections and laser treatment may be recommended.

In this video, an eye doctor explains diabetic eye disease. (Video: National Eye Institute)


In this video, Rep. James Clyburn asks African-American diabetics to get annual eye exams.

In 2012, the FDA announced approval of monthly injections of Lucentis (ranibizumab) for treatment of DME. Lucentis is a steroidal anti-VEGF medication marketed by Genentech.

FDA approval was based on positive two-year outcomes of two studies wherein 759 patients received monthly eye injections of 0.3 mg Lucentis, 0.5 mg Lucentis or a drug-free (sham) injection.

Pooled results 24 months after the initial injections revealed 39.2 percent of patients who received monthly injections of 0.3 mg ranibizumab and 42.5 percent of those who received the 0.5 mg dose gained at least 15 letters in best corrected visual acuity (BCVA) on a standard eye chart, compared with 15.2 percent of patients in the sham group.

One study — called the RESTORE study — also found that Lucentis injections alone and Lucentis injections combined with laser treatment were both significantly more effective than laser treatment alone for the treatment of DME. One year after initiation of treatment 53 percent of patients in the Lucentis-only group and 44.9 percent of those in the combined Lucentis and laser group had better than 20/40 BCVA, compared with only 23.6 percent in the laser-only group.

Steroid implants are medical devices that are injected into the eye and held in place by the pressure of the eye's clear, gel-like fluid (vitreous) that fills the back cavity (posterior chamber) of the eye.

One such device used to treat DME is the Iluvien implant, marketed by Alimera Sciences. After injection into the eye, the implant provides a sustained release of a corticosteroid (fluocinolone acetonide) to reduce macular swelling and inflammation.

Though not yet FDA-approved for use in the U.S., in late-stage clinical trials about 40 percent of 123 participants with DME had vision improvement within 30 months of implantation of the Iluvien device.

Other commercially available intravitreal steroid implants that may be used off label include Retisert (Bausch + Lomb) and Ozurdex (Allergan). Retisert contains fluocinolone acetonide, and Ozurdex contains dexamethasone. However, neither of these implants have specific FDA approval for treatment of diabetic macular edema at this time.

Risks associated with intraocular steroid treatment for DME include steroid-induced cataracts and glaucoma. Vision loss from cataracts usually can be restored with cataract surgery if necessary. To reduce the risk of glaucoma, your eye doctor might recommend preventive use of glaucoma eye drops or even glaucoma surgery.

Vitrectomy and Other Surgery Treatments for Diabetic Eye Disease

In some people who have proliferative diabetic retinopathy, bleeding into the vitreous (vitreous hemorrhage) prevents the ophthalmologist from performing the laser treatment, because the blood blocks the laser beam.

If the vitreous hemorrhage fails to clear within a few weeks or months, a vitrectomy surgery may be performed to mechanically remove the hemorrhage — after which, laser photocoagulation can be applied. The laser procedure is performed either at the time of the vitrectomy or shortly thereafter.

Retinal bleeding and vitreous hemorrhage also can cause bands of scar tissue to form. These bands of scar tissue can shrink and — if attached to the retina — can cause the retina to pull away from its base to create traction.

This traction may lead to retinal tears or possible retinal detachments.

If you experience a tractional detached retina as part of PDR and shrinking scar tissue that tugs at the retina, you usually will be scheduled promptly for a procedure to reattach the retina.

ETDRS guidelines show that type 2 diabetics in particular can reduce their chance of severe vision loss and the need for vitrectomy surgery by about 50 percent when proliferative diabetic retinopathy is treated before it reaches a high-risk stage.

Steroid Eye Drops for Diabetic Macular Edema

Some individuals with diabetic macular edema may experience reduced symptoms and improved vision after treatment with corticosteroid medication delivered to the eye via eye drops rather than an intraocular implant.

In a study published in Acta Ophthalmologica in November 2012, researchers found that patients with diffuse DME who used Durezol emulsion eye drops (Alcon) four times a day for one month had reduced retinal swelling and a significant improvement in visual acuity, compared with similar DME patients who did not use the eye drops.

Durezol is a corticosteroid eye drop used primarily for the treatment of inflammation and pain associated with eye surgery.

The study authors concluded that use of Durezol eye drops is a useful and effective treatment for diffuse DME without surgical intervention and the associated risk of potentially severe side effects.

Experimental Treatments for Diabetic Eye Disease

Due to the continuing growth of diabetes and the increasing number of people at risk for vision loss from diabetic eye disease, many companies are actively involved in developing new treatments for diabetic retinopathy and macular edema.

Experimental treatments that are showing promise for the control of diabetic eye disease involve the use of anti-VEGF drugs. These medicines, which are injected into the eye, also are used to treat advanced age-related macular degeneration.

One such drug being co-developed by Regeneron Pharmaceuticals and Bayer HealthCare is called VEGF Trap-Eye.

After promising early study results, the companies announced in April 2011 that Bayer has initiated a late-stage clinical trial of VEGF Trap-Eye in Australia for the treatment of diabetic macular edema. The trial also will be conducted in Europe and Japan.

A second study of VEGF Trap-Eye for the treatment for DME led by Regeneron is expected to begin later in 2011 in the United States, Canada and other countries. The companies also are conducting clinical studies of VEGF Trap-Eye (also called Eylea) for the treatment of central retinal vein occlusion (CRVO), a type of eye stroke. In November 2011 Eylea gained FDA approval for treatment of neovascular ("wet") macular degeneration.

University of Georgia researchers announced in early 2011 that experiments using diabetic rats show a statin anti-cholesterol drug (Lipitor) helped prevent damage from diabetic retinopathy by blocking formation of free radicals and protecting neurons in the retina.

Early study results from another experimental treatment known as NCX 434 (NicOx) were announced in June 2010 at the Retina International World Congress in Stresa, Italy.

The company describes the treatment as a "nitric oxide (NO)-donating new molecular entity" capable of reducing retinal damage related to lack of blood and oxygen (ischemia) caused by diabetic macular edema.

Also in June 2010, Eyetech announced positive late-stage clinical trial results for its anti-VEGF drug, Macugen (pegaptanib sodium).

At 54 weeks, 37 percent of study participants with diabetic macular edema improved visual acuity by at least two lines on an eye chart, compared with 20 percent who received a placebo injection. Researchers enrolled 260 participants for the study.

In the major ACCORD Eye Study sponsored by the National Institutes of Health, extensive blood sugar control combined with cholesterol-lowering drugs reduced the progression of diabetic eye disease by about one-third over a four-year period. Results of the eye portion of the study involving 2,856 people were announced in April 2010.

[Page updated May 2013]