CONTROVERSY EXISTS among experienced clinicians as to whether one should ever recommend focal and/or grid photocoagulation for eyes with clinically significant diabetic macular edema and visual acuity of 20/20 or better. When experienced clinicians disagree, there is usually good reason for the disagreement. What information exists to help us decide when, if ever, to recommend such treatment?
The rationale for treating eyes with good visual acuity comes largely from Early Treatment Diabetic Retinopathy Study (ETDRS) reports. In that study, the demonstration of a beneficial effect of photocoagulation for macular edema was based on the comparison of eyes with mild to moderate nonproliferative diabetic retinopathy and macular edema that were randomly assigned to have either focal and/or grid photocoagulation or no photocoagulation for the macular edema. Comparisons between treated and control group eyes demonstrated that the group assigned to photocoagulation for clinically significant diabetic macular edema had a 50% reduction of moderate visual loss (defined as a doubling or more of the initial visual angle or ≥3-line worsening in visual acuity on a logarithmic eye chart). This benefit of photocoagulation was present regardless of the initial level of visual acuity (patients with visual acuity worse than 20/200 were not eligible for the study). In addition, photocoagulation for macular edema only infrequently resulted in recovery of visual acuity that had been lost prior to treatment.1 Based on these observations, it seems prudent not to wait too long before initiating photocoagulation, for fear that once lost, good visual acuity may never be recovered. Published reports from the ETDRS include a recommendation that photocoagulation should be considered for all eyes with clinically significant macular edema. Factors involved in that consideration include the extent and source (focal or diffuse) of retinal thickening, the extent and location of hard exudates, the change in edema from a previous visit, current visual acuity, and the possible need for scatter photocoagulation or cataract extraction. In addition, the status of the fellow eye should be considered along with systemic factors such as hypertension, renal status, and serum lipid levels, and personal factors, particularly the ability to maintain appropriate follow-up.
Ferris FL, Davis MD. Treating 20/20 Eyes With Diabetic Macular Edema. Arch Ophthalmol. 1999;117(5):675-676. doi:10.1001/archopht.117.5.675