Computer-Assisted Measurement of Retinal Vascular Width and Tortuosity in Retinopathy of Prematurity

Objectives: To validate the accuracy of ROPtool software in measuring retinal vascular width and tortuosity in a large image set compared with expert diagnoses. Methods: Tortuosity and dilation indexes generated by ROPtool were compared with 3 expert consensus grades of normal, pre-plus, or plus disease for 368 quadrants in 92 RetCam (Clarity Medical Systems, Pleasanton, California) fundus images. Sensitivity and specificity of ROPtool software in diagnosing tortuosity and dilation sufficient for plus and pre-plus disease were calculated. These measures were compared with individual accuracies of 3 experienced pediatric ophthalmologists. Results: The mean tortuosity indexes for expert-diagnosed categories of normal, pre-plus, and plus disease were 7.04, 18.73, and 34.62, respectively (P<.001), and the mean dilation indexes were 9.63, 12.05, and 13.61, respectively (P<.001). When optimal tortuosity and dilation index thresholds (from receiver operating characteristic curves) were applied, resultant sensitivity and specificity were 0.913 and 0.863, respectively, for plus tortuosity and 0.782 and 0.840, respectively, for plus dilation. These values were comparable to the performance of examiners judged against the same expert panel. Conclusion: ROPtool version 2.1.5 accurately measures tortuosity and dilation of posterior pole blood vessels in RetCam images, corresponding well with expert diagnostic categories of normal, pre-plus, and plus disease and performing comparably to experienced examiners.