Purpose: Comparison of Diabetic macular edema estimation using slit lamp biomicroscopy versus that using OCT.

Materials and Methods: We performed a retrospective analysis of 121 patients (154 eyes) with established Type 2 diabetes mellitus, divided into three groups. Group I consisted of 62 eyes with NPDR, Group II ,27 eyes with PDR and  Group III ,66 eyes with CSME. Diagnosis of CSME was made as per ETDRS protocol, using slit lamp stereoscopic biomicroscopy. DME was defined on OCT as central foveal thickness greater than 250µm .OCT scanning was performed through the macula of each eye after pupillary dilatation.


Results: The mean age of patients included was 60.70 ± 9.20years and 61.98% were males. Only 66 eyes were classified as having DME clinically as opposed to 109 eyes by OCT, leading to a significant sub-estimation of 39.44% eyes. The mean macular thickness in the CSME patients identified by slit lamp biomicroscopy was 399.59±105.31µm.The mean central macular thickness in the sub-estimated cases was 290.58 ±28.92 µm overall, 290.10±26.19 µm in the PDR group and 290.95± 31.46µm amongst NPDR patients.

Conclusion: Mild macular thickening on OCT may not correspond to overt edema clinically and has been termed sub-clinical macular edema by some authors. We report a sub- estimation of DME in 39.44% eyes in our study. The emerging importance of monitoring of these vulnerable patients and early detection of their conversion to overt CSME must be realised. In conclusion, assessment of diabetic macular edema with OCT is probably more objective and reliable.