Screening for glaucoma using GDx-VCC in a population with ≥1 risk factors

Abstract Objective To estimate the diagnostic accuracy of the GDx-VCC for glaucoma screening in a population with ≥1 risk factors for glaucoma. Design Cross-sectional evaluation of a diagnostic test for screening. Participants Two hundred forty-seven community-based volunteer participants with risk factors for glaucoma. Methods The peripapillary retinal nerve fibre layers (RNFL) of participants’ eyes were scanned using the GDx-VCC. Based on an ophthalmologic examination and frequency doubling perimetry, eyes were classified into 4 categories: normal, possible glaucoma, probable glaucoma, and definitive glaucoma. The sensitivities, specificities, positive and negative predictive values, and positive and negative likelihood ratios of the RNFL parameters were calculated. Results The right eyes were retained for analyses. After excluding 5 eyes because of missing data and 23 eyes because of poor scan quality, the data of 219 right eyes were analyzed. Four eyes had definitive glaucoma. The best performing parameter was the nerve fibre indicator using a cutoff of 35 with a sensitivity of 75% (95% CI 19.4–99.4) at a specificity of 95% (95% CI 91.3–97.3), a positive predictive value of 25 (95% CI 4.3–48.1), a negative predictive value of 99 (95% CI 97.5–100.0), a positive likelihood ratio of 16 (95% CI 6.69–32.5), and a negative likelihood ratio of 0.20 (95% CI 0.05–1.44). Conclusions The GDx-VCC has inadequate sensitivity for screening of definitive glaucoma.