Purpose: Plus disease is severely abnormal dilation and tortuosity of posterior retinal blood vessels in infants with retinopathy of prematurity (ROP). It has become the major criterion for laser treatment in ROP, but its assessment is subjective and prone to error. ROPtool is a computer program that traces retinal blood vessels, measures their tortuosity, and determines whether there is sufficient tortuosity for plus disease. The purpose of this study was to prospectively determine if assessment of tortuosity by ROPtool is more accurate than by individual pediatric ophthalmologists.
Methods: One hundred eighty-five high-quality RetCam images from premature infants were circulated to 3 ROP experts to develop reference data and to 3 other pediatric ophthalmologists ("examiners") who graded the tortuosity in each quadrant as normal, pre-plus, or plus. These same images were analyzed using ROPtool. Overall accuracy, sensitivity, and specificity of ROPtool relative to expert consensus were compared to that of the individual examiners.
Results: By expert consensus, 37 of the 185 eyes (20%) had tortuosity sufficient for plus disease. The overall accuracy of ROPtool of 95% (175/185) for identifying tortuosity sufficient for plus disease was similar to that of examiner 1 (93%, 172/185, P = .5), examiner 2 (93%, 172/185, P = .5), and examiner 3 (91%, 168/185, P = .1). Sensitivity of ROPtool of 97% (36/37) was superior to that of examiner 1 (65%, 24/37, P < .001), examiner 2 (70%, 26/37, P < .001), and examiner 3 (81%, 30/37, P = .02). The mean tortuosity of quadrants with plus disease was 19.1 tortuosity units, compared to 9.9 tortuosity units for quadrants with pre-plus (P < .001) and 4.8 tortuosity units for normal quadrants (P < .001 for pre-plus vs normal).
Conclusions: ROPtool has excellent sensitivity and overall accuracy relative to expert consensus in the detection of tortuosity sufficient for plus disease. Computer-assisted analysis of retinal images has the potential to remove subjectivity from the determination of plus disease and to optimize the timing of follow-up and treatment for ROP.