Diabetic macular edema: correlation between microperimetry and optical coherence tomography findings

PURPOSE: To compare the changes in macular sensitivity (microperimetry) and macular thickness with different degrees of diabetic macular edema. METHODS: Sixty-one eyes of 32 consecutive diabetic patients were included in this cross-sectional study. All included eyes underwent functional and morphologic examination of the macular area. Best corrected visual acuity (ETDRS charts), macular sensitivity, and macular thickness were quantified. Lesion-related macular sensitivity and retinal fixation were investigated with an advanced, automatic microperimeter. Optical coherence tomography (OCT) was used to quantify macular thickness. RESULTS: The 61 included eyes were graded, by two retinal specialists, for diabetic macular edema as follows: 16 were graded as no macular edema (NE), 30 as non-clinically significant macular edema (NCSME), and 15 as clinically significant macular edema (CSME). Macular thickness significantly increased from the NE to the CSME group (P<0.0001), whereas macular sensitivity significantly decreased from the NE to the CSME group (P<0.0021). A significant correlation coefficient was noted between retinal sensitivity and normalized macular thickness (r=-0.37, P<0.0001). Linear regression analysis showed a decrease of 0.83 dB (P<0.0001) for every 10% of deviation of retinal thickness from normal values. Visual acuity and central macular sensitivity correlated significantly in the NCSME group (r=-0.6, P=0.0008), but not in the NE (r=-0.144, P=0.6) or in the CSME (r=-0.46, P=0.11) groups. CONCLUSIONS: Macular edema may be better documented by adding macular sensitivity mapping by microperimetry to macular thickness measurement by OCT and visual acuity determination because macular sensitivity seems to be a relevant explanatory variable of visual function, independent of macular thickness data. Moreover, microperimetry may be of value in predicting the outcome of diabetic macular edema, because it incorporates a functional measure that may supplement the predictive value of OCT and visual acuity.