Preliminary Assessment of Laser and Medical Treatment of Diabetic Macular Edema

This study will compare the side effects of two laser treatments for diabetic macular edema, a common condition in patients with diabetes. In macular edema, blood vessels in the retina-a thin layer of tissue that lines the back of the eye-become leaky and the retina swells. The macula-the center part of the retina that is responsible for fine vision-may also swell and cause vision loss. Traditional laser treatment (argon blue or green or yellow) for macular swelling, or edema, causes scarring that can expand and possibly lead to more loss of vision. Studies with a different type of laser (diode) have shown no adverse effects to the retina, but long-term effects of this treatment are not known. The results of this study on side effects of the treatments will be used to design a larger study of effectiveness. This study will also examine whether vitamin E can reduce the damage caused by laser treatment. Patients with diabetic eye disease who take vitamin E have increased blood flow through the vessels of the retina, as well as improved kidney function. Patients with elevated cholesterol levels will be invited to participate in a cholesterol reduction part of the study to compare normal-pace cholesterol reduction with accelerated reduction.

Patients 18 years of age and older with type 1 or type 2 diabetes and macular edema may be eligible for this study. Candidates will be screened with the following tests and procedures:

• Medical history - to review past medical conditions and treatments.
• Physical examination - to measure vital signs (pulse, blood pressure, temperature, breathing rate) and examine the head and neck, heart, lungs, abdomen, arms and legs.
• Eye examination - to assess visual acuity (eye chart test) and examine pupils, lens, retina, and eye movements. The pupils will be dilated with drops for this examination.
• Blood tests - to measure cholesterol and vitamin E blood levels, blood clotting time, hemoglobin A1C (a measure of diabetes control), and to evaluate liver and kidney function.
• Photography - to help evaluate the status of the retina and changes that may occur in the future. Special photographs of the inside of the eye are taken using a camera that flashes a bright light into the eye. From 2 to 20 pictures may be taken, depending on the eye condition.
• Fluorescein angiography - to evaluate the eye's blood vessels. A yellow dye is injected into an arm vein and travels to the blood vessels in the eyes. Pictures of the retina are taken using a camera that flashes a blue light into the eye. The pictures show if any dye has leaked from the vessels into the retina, indicating possible blood vessel abnormality.

Participants will be randomly assigned to receive one of the two laser treatments. They will also be randomly assigned to take 1600 IU of vitamin E or placebo (an inactive, look-alike pill) daily. For the laser treatment, eye drops are put in the eye to numb the surface and a contact lens is placed on the eye during the laser beam application. Several visits may be required for additional laser treatments. The maximum number of treatments depends on how well the treatment is working.

On their first visit, patients will be given vitamin C. After taking the vitamin for 1 month, they will return to the clinic for the first laser treatment. They will followed 1, 3, 6, 9, and 12 months after the first treatment, and then every 6 months until either 1) the patient returns for a 3-year visit; 2) the last enrolled patient returns for the 1-year visit, or the patient requests to leave the study. During these visits, several of the exams described above will be repeated to evaluate the response to treatment and check for side effects of the vitamin E.