Comparison of vertical cup-to-disc ratio estimates using stereoscopic and monoscopic cameras

The use of monoscopic cameras for glaucoma screening is increasing due to their portability, lower cost, and non-mydriatic capabilities. However, it is important to compare the accuracy of such devices with stereoscopic cameras that are used clinically and are considered the gold standard in optic disc assessment. The aim of this study is to compare vertical cup-to-disc ratio (VCDR) estimates obtained using images taken with a monoscopic and stereoscopic camera.

Participants were selected from the Tema Eye Survey. Eligible subjects had images of at least one eye taken with two cameras. They were classified as meeting the glaucoma threshold if an eye had a VCDR estimate >97.5th percentile, corresponding to >0.725 for this population. Hence, we used 0.725 as the cutoff to group eyes into two categories: positive and negative. We calculated sensitivity, specificity, and predictive values of VCDR assessed by expert readers at a reading center for monoscopic photos using stereoscopic photos as the gold standard.

Three hundred and seventy-nine eyes of 206 participants were included in the study. Most participants were female (60.2%) and the most common age group was 50-59 years (36.4%). Sixteen eyes met the glaucoma threshold (VCDR > 0.725). Of these, the VCDR estimates of 14 eyes (87.5%) disagreed on the glaucoma threshold from the two cameras. The sensitivity to detect glaucoma with the monoscopic camera was 14.3% (95% CI: 4.0, 40.3).

The low sensitivity of monoscopic photos suggests that stereoscopic photos are more useful in the diagnosis of glaucoma.