Extent of diabetic macular edema by scanning laser ophthalmoscope in the retromode and its functional correlations

Background: To determine whether scanning laser ophthalmoscope in the retromode (RM-SLO) is useful to evaluate the extent of diabetic macular edema (DME) and its functional characteristics.Methods: Comparative case series of 37 eyes (27 patients with diabetes). Inclusion criteria were: center involving DME determined by optical coherence tomography; RMSLO, optical coherence tomography, fluorescein angiography (FA), and microperimetry performed on the same day; no significant media opacities. Two masked retinal specialists independently graded all images. The full extent of DME areas and two grades (small and large) DME areas were separately evaluated. The relationship between the DME extent obtained by RM-SLO and FA was assessed by Pearson correlation coefficient, intraclass correlation coefficient, and Bland-Altman plot. T-test was used to compare DME extent to central retinal thickness and macular sensitivity.Results: The values of RM-SLO from the right and left prospective were highly correlated in the evaluation of the extent of DME (rho = 0.99, P < 0.0001). Mean DME area on RM-SLO was 5.7 + 5.6 mm2 (range, 0.3-18.2 mm2); mean DME area on FA was 6.4 + 5.9 mm2 (range, 0.3-19.7 mm2). The correlation between RM-SLO and FA in the evaluation of DME extent was highly significant (rho = 0.97, P < 0.0001), even when DME extent was divided in 2 major areas (intraclass correlation coefficient >0.8, P < 0.0001). The correlation between retinal sensitivity and DME area (RM-SLO) was significant (rho = -0.61, P = 0.0003).Conclusion: The extent has become an important parameter for monitoring DME, with or without treatment. The extent of DME well correlates with functional data, mainly retinal sensitivity. Retromode SLO can be reliably and easily used in the evaluation of DME extent, avoiding the use of invasive FA.