Treatment of Diabetic Macular Edema: Triamcinolone Injections Vs. Laser Photocoagulation

This study will compare the side effects of two treatments for diabetic macular edema, in which blood vessels in the retina (tissue that lines the back of the eye) become leaky and the retina and macula (the center part of the retina that is responsible for fine vision) swell, causing vision loss. Patients 18 years of age and older with diabetes mellitus and macular edema in one or both eyes may be eligible for this study. Candidates are screened with the following tests and procedures: * Blood pressure measurement. * Blood tests to measure HbA1c, a measure of the patient's diabetes control. * Eye examination to assess visual acuity and eye pressure, and to examine pupils, lens, retina and eye movements. The pupils are dilated with drops for this examination. * Eye photography to help evaluate the status of the retina and changes that may occur in the future. Photographs of the inside of the eye are taken using a camera that flashes a bright light into the eye. * Electroretinograms (ERG) to measure electrical responses generated in the retina. Wearing eye patches, the patient sits in a dark room for 30 minutes. Then, electrodes are taped to the forehead and an earlobe. The eye patches are removed, the surface of the eye is numbed with eye drops, and contact lenses are placed on the eyes. The patient looks inside a white globe that emits a series of light flashes for about 20 minutes. The contact lenses sense small electrical signals generated by the retina when the light flashes. * Optical coherence tomography to measure retinal thickness. The eye is examined with a machine that produces cross-sectional pictures of the retina. These measurements are repeated during the study to determine whether retinal thickening is improving, worsening, or staying the same. Patients with macular edema in both eyes receive laser therapy in one eye and triamcinolone injections in the other. Patients with just one affected eye are randomly assigned to receive either laser or triam