Glaucoma Screening in Nepal: Cup-to-Disc Estimate With Standard Mydriatic Fundus Camera Compared to Portable Nonmydriatic Camera

Abstract

To compare cup-to-disc ratio (CDR) measurements from images taken with a portable, 45-degree nonmydriatic fundus camera to images from a traditional tabletop mydriatic fundus camera. Prospective, cross-sectional, comparative instrument validation study. Setting: Clinic-based. A total of 422 eyes of 211 subjects were recruited from the Tilganga Institute of Ophthalmology (Kathmandu, Nepal). Two masked readers measured CDR and noted possible evidence of glaucoma (CDR ≥ 0.7 or the presence of a notch or disc hemorrhage) from fundus photographs taken with a nonmydriatic portable camera and a mydriatic standard camera. Each image was graded twice. Effect of camera modality on CDR measurement; inter- and intraobserver agreement for each camera for the diagnosis of glaucoma. A total of 196 eyes (46.5%) were diagnosed with glaucoma by chart review; 41.2%-59.0% of eyes were remotely diagnosed with glaucoma over grader, repeat measurement, and camera modality. There was no significant difference in CDR measurement between cameras after adjusting for grader and measurement order (estimate= 0.004, 95% confidence interval [CI], 0.003-0.011, P= .24). There was moderate interobserver reliability for the diagnosis of glaucoma (Pictor: κ= 0.54, CI, 0.46-0.61; Topcon: κ= 0.63, CI, 0.55-0.70) and moderate intraobserver agreement upon repeat grading (Pictor: κ= 0.63 and 0.64, for graders 1 and 2, respectively; Topcon: κ= 0.72 and 0.80, for graders 1 and 2, respectively). A portable, nonmydriatic, fundus camera can facilitate remote evaluation of disc images on par with standard mydriatic fundus photography.