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

Diabetic Macular Edema, Diabetic Retinopathy, DME

Steroid, Diabetic Macular Edema, DME

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 triamcinolone treatment. Those who receive only laser therapy may later receive triamcinolone injections in the second eye if it, too, develops macular edema. For the laser treatment, the eye surface is numbed with drops and a contact lens is placed on the eye during the laser beam application. Before the treatment, patients may have fluorescein angiography, in which pictures of the retina are taken using a yellow dye. The dye is injected into a vein and travels to the blood vessels in the eye. The camera flashes a blue light in the eye and takes pictures that show the amount of dye leakage into the retina. This helps guide the laser treatment. Patients return for follow-up visits every 4 months for 3 years. If the macular edema is gone, no additional treatment is given and patients are followed as often as every 2 months. If the edema does return, additional treatments may be done at subsequent visits. Patients whose vision worsens considerably at the end of 1 year may be treated with a steroid injection, unless the other eye has also been treated with triamcinolone. For the triamcinolone injections, numbing drops, antibiotic drops, and drops to dilate the pupil, and possibly and anesthetic injection, are put in the eye before the medicine is injected into the vitreous (jelly-like substance inside the eye). Then, the patient lies on his or her back for 30 minutes before being discharged home. Patients return for follow-up visits 4 days and 4 weeks after the injection, and then every 4 months for 3 years. Patients whose edema resolves are followed as often as every 2 months. Those whose edema returns have additional injections at the 4-month visits. Patients whose condition does not improve after 1 year or whose vision worsens may undergo laser treatment.

Diabetic retinopathy is a major cause of visual impairment in the United States. Diabetic Macular edema (DME) is a manifestation of diabetic retinopathy that produces loss of central vision. Data from the Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR) estimate that after 15 years of known diabetes, the prevalence of diabetic macular edema is approximately 20% in patients with type 1 diabetes mellitus (DM), 25% in patients with type 2 DM who are taking insulin, and 14% in patients with type 2 DM who do not take insulin. In a review of three early studies concerning the natural history of diabetic macular edema, Ferris and Patz found that 53% of 135 eyes with diabetic macular edema, presumably all involving the center of the macula, lost two or more lines of visual acuity over a two year period. In the Early Treatment Diabetic Retinopathy Study (ETDRS), 33% of 221 untreated eyes available for follow-up at the 3-year visit, all with edema involving the center of the macula at baseline, had experienced a 15 or more letter decrease in visual acuity score (equivalent to a doubling of the visual angle, e.g., 20/25 to 20/50, and termed moderate visual loss). The frequency of an unsatisfactory outcome following laser photocoagulation in some eyes with diabetic macular edema has prompted interest in other treatment modalities. One such treatment is pars plana vitrectomy. These studies suggest that vitreomacular traction, or the vitreous itself, may play a role in increased retinal vascular permeability. Removal of the vitreous or relief of mechanical traction with vitrectomy and membrane stripping may be followed by substantial resolution of macular edema and corresponding improvement in visual acuity. However, this treatment may be applicable only to a specific subset of eyes with diabetic macular edema. It also requires a complex surgical intervention with its inherent risks, recovery time, and expense. Other treatment modalities such as pharmacologic therapy with oral protein kinase C inhibitors and antibodies targeted at vascular endothelial growth factor (VEGF) are under investigation. The use of intravitreal corticosteroids is another treatment modality that has generated recent interest.

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