Purpose: To define the course of subclinical diabetic macular edema (DME) and identify any predictors of progression to clinically significant DME.
Design: Retrospective, observational case series.
Setting: Private retina practice.
Patient population: One hundred and fifty-three eyes of 153 patients with diabetic retinopathy and subclinical DME.
Observation procedures: Clinical charts review and longitudinal optical coherence tomography (OCT) measurements.
Main outcome measures: Change in OCT values and time to eventual treatment for clinically significant DME.
Results: Over a median follow-up of 14 months (interquartile range, seven to 25 months), 48 of 153 eyes (31.4%) progressed to clinically significant DME. The numbers (%) of eyes showing decreased, unchanged, and increased central subfield mean thickness were 16 (10.5%), 117 (76.5%), and 20 (13.1%), respectively. None of the patients or eye variables typically assessed in clinical practice was predictive of progression from subclinical DME to clinically significant DME.
Conclusions: Progression from subclinical DME to clinically significant DME may be detected by serial clinical and OCT assessment. Subclinical DME does not inexorably progress over time scales of one to two years, and a substantial fraction of eyes spontaneously improve. Follow-up intervals of four to six months allowed detection of progression to clinically significant DME. In this sample of patients, OCT did not help in predicting which eyes with subclinical DME would progress to clinically significant DME.