Diagnostic Accuracy of Digital Retinal Fundus Image Analysis in Detecting Diabetic Maculopathy in Type 2 Diabetes Mellitus

Background: Digital retinal imaging is the gold standard technique for diabetic retinopathy (DR) and diabetic macular oedema (DME) assessment during DR screening. Objectives: To evaluate the diagnostic accuracy of digital retinal fundus image (DRFI) analysis in detecting DME using three manual grading systems (MGS) and comparing it with optical coherence tomography (OCT) findings. Method: A total of 287 DRFI of 287 eyes were analysed. Non-stereoscopic 45° images were acquired using a Kowa VX-20 camera and were graded according to three MGS: Early Treatment Diabetic Retinopathy Study (ETDRS), International Clinical Diabetic Retinopathy (ICDR), and United Kingdom National Screening Committee (UKNSC). The two graders were masked to the patient's clinical DR status. DME characteristics were analysed using OCTs. Results: A very good agreement in detecting DME was found with Cohen's κ = 0.83 (ICDR vs. ETDRS), κ = 0.83 (ICDR vs. UKNSC), and κ = 0.82 (ETDRS vs. UKNSC). Sensitivity and specificity of DRFI analysis in DME assessment were 70.0 and 69.6% for UKNSC, 71.9 and 67.4% for ETDRS, and 70.9 and 65.2% for ICDR, respectively. Positive and negative predictive values were 91.7 and 32.7% for UKNSC, 91.4 and 33.3% for ETDRS, and 90.7 and 31.9% for ICDR, respectively. On OCT scans, micro-architectural damages of both inner and outer retinal layers and mean ganglion cell layer thickness showed a significant association with the presence of DME detected with DRFI analysis. Conclusions: Despite the low negative predictive value, the good specificity and sensitivity of DRFI in detecting DME make it a useful tool in a routine clinical setting, and its potential in diabetic eye screening is yet to be realized.