Accuracy of computer-assisted vertical cup-to-disk ratio grading for glaucoma screening

Purpose Glaucoma screening can be performed by assessing the vertical-cup-to-disk ratio (VCDR) of the optic nerve head from fundus photography, but VCDR gradingis inherently subjective. This study investigated whether computer software could improve the accuracy and repeatability of VCDR assessment. Methods In this cross-sectional diagnostic accuracy study, 5 ophthalmologists independently assessed the VCDR from a set of 200 optic disk images, with the median gradeused as the reference standard for subsequent analyses. Eight non-ophthalmologists gradedeach image by two different methods: by visual inspectionand with assistance from a custom-made publicly available software program. Agreement with the reference standard gradewas assessed for each method by calculating the intraclass correlation coefficient (ICC), and the sensitivity and specificity determined relative to a median ophthalmologist gradeof ≥0.7. Results VCDR gradesranged from 0.1 to 0.9 for visual assessment and from 0.1 to 1.0 for software-assisted grading, with a median gradeof 0.4 for each. Agreement between each of the 8 graders and the reference standard was higher for visual inspection(median ICC 0.65, interquartile range 0.57 to 0.82) than for software-assisted grading(median ICC 0.59, IQR 0.44 to 0.71); P = 0.02, Wilcoxon signed-rank test). Visual inspectionand software assistance had similar sensitivity and specificity for detecting glaucomatous cupping. Conclusion The computer software used in this study did not improve the reproducibility or validity of VCDR gradingfrom fundus photographs compared with simple visual inspection. More clinical experience was correlated with higher agreement with the ophthalmologist VCDR reference standard.