Purpose: To determine estimates of the magnitude and time course of macular thinning induced by three interventions for diabetic macular edema (DME).
Design: Retrospective observational case series.
Participants: Two hundred eleven eyes of 133 patients of a private retina practice, each diagnosed with DME in > or =1 eye.
Methods: Review of clinical charts and optical coherence tomography measurements of eyes receiving focal laser photocoagulation, intravitreal triamcinolone injection (IVTA), or vitrectomy compared to untreated fellow eyes without DME.
Main outcome measures: Central subfield mean thickness (CSMT; in micrometers), total macular volume (cubic millimeters), visual acuity, and rates of increased macular thickening at follow-up.
Results: At 6 months follow-up, predicted change in CSMT is 0 mum for untreated fellow eyes without DME, -28 mum for eyes receiving focal laser, -83 mum for eyes receiving triamcinolone, and -92 mum for eyes receiving vitrectomy. The predicted change in Early Treatment Diabetic Retinopathy Study letters read at 6 months is 0 for untreated fellow eyes without DME, 0 for eyes receiving focal laser, +3 for eyes receiving IVTA, and -1 for eyes receiving vitrectomy. Increased thickening of the macula after interventions designed to thin it were 25.4% for focal laser, 3.8% for IVTA, and 19.0% for vitrectomy.
Conclusions: Interventions for DME differ in effect size, durability of effects, and potential for subsequent increases in macular thickness. A prospective study to elucidate a preferred sequence of interventions in DME may be worthwhile.