Types of diabetic macular edema assessed by optical coherence tomography

Abstract

Aim: To assess the types of diabetic macular edema (DME) in patients with type 2 diabetes mellitus by analyzing retinal thickness, morphology and presence of macular traction using optical coherence tomography (OCT).

Patients and methods: This prospective study included 74 diabetics with diabetic retinopathy (DR) (141 eyes), 29 diabetics without DR (57 eyes) and 25 healthy volunteers (39 eyes). The ophthalmic examination included best corrected visual acuity, stereo-ophthalmoscopy, fluorescein angiography and OCT. DME assessment was based on the analysis of several OCT features: macular thickness, retinal morphology and presence of macular traction--vitreomacular and/or from epiretinal membranes. Four OCT types of DME were suggested: type 1--early, type 2--simple, type 3--cystoid (3a--mild, 3b--intermediate, 3c--severe) and type 4--serous macular detachment. The distribution of the DME types and their correlation with retinal thickness and visual acuity were analyzed.

Results: The distribution of eyes with DME was: type 1--14.1%, type 2--30.4%, type 3--45.7% (3a--14.1%, 3b--12%, 3c--19.6%) and type 4--9.8%. Macular traction with retinal distortion was detected in 31.5% of the eyes with DME. Retinal thickness at the fixation point was 176 +/- 16.8 microm (116 microm / 210 microm) in healthy eyes and 182.2 +/- 19.6 microm (138 microm / 212 microm) in eyes without DR. There was no statistically significant difference between the two groups (Independent samples test, P > 0.05). The retina was significantly thicker in eyes with early DME (232.9 +/- 7.9 microm) than in healthy eyes and eyes without DR (Independent samples test, F = 16.274 and F = 13.100, P < 0.0001). Increasing retinal thickness was significantly correlated with worse visual acuity (ANOVA, F = 16.692, P < 0.0001).

Conclusion: OCT precisely differentiated 4 types of DME: early, simple, cystoid and serous macular detachment, as well as determined the presence of macular traction. The early diagnosis, high precision in retinal thickness measurement, assessment of the morphologic types and macular traction are of uppermost importance in determining the therapeutic approach, prognosis and the effect of treatment.