PRCIS: Using optical coherence tomography measurements as a reference standard for vertical cup-to-disc ratio (vCDR), a smartphone-based ophthalmic camera has a sensitivity of 67.7% and specificity of 96.7% to detect a vCDR greater than 0.5.
PURPOSE: The purpose of this study was to assess the performance of a smartphone-based ophthalmic camera system using an Apple iPhone 6S and an adapter, Paxos Scope, to obtain adequate dilated fundus photos in order to measure clinically useful vertical cup-to-disc ratio (vCDR) cutoffs.
PATIENTS AND METHODS: Adult patients from a government tertiary level eye hospital in southwestern Uganda were prospectively recruited from January to April 2019. All patients experienced a comprehensive eye examination, dilated posterior segment indirect ophthalmoscope imaging with the Paxos Scope, and spectral domain optical coherence tomography (SDOCT) imaging with a Cirrus HD-OCT to measure vCDR. Patients' eyes excluded had media opacities or existing disease precluding a view of the fundus. Fundus images underwent a single masked review to assign vCDR at increments of 0.1. Descriptive statistics, parametric and Chi2 tests for significance, repeated measures correlation, kappa, receiver operating characteristics (ROC), and Bland-Altman were used to assess the data.
RESULTS: Among 467 (consecutive) individuals, fundus photographs acquired with the Paxos Scope demonstrated a 67.7% (95%CI 63.0-72.0) sensitivity and 96.7% (95%CI 94.2-98.3) specificity to detect a vCDR >0.5, using OCT as the reference standard. 138 eyes were excluded due to poor imaging acquisition, such as dense cataract, rendering 796 eyes for analysis. The vCDR from graded Paxos Scope images and OCT correlated well with repeated measures correlation of 0.82 (95%CI, 0.77-0.86, P0.5 or ≤0.5, was 80.9% (kappa=0.63±0.034, P0.5 were 97.5% (95%CI, 91.3-99.7) and 80.0% (95%CI, 28.4-99.5), respectively. The area under the receiver operating characteristics curve (AROC) was 0.92 (95% CI, 0.89-0.94) for all eyes and 0.98 (95%CI, 0.78-1.0) for glaucoma and glaucoma suspects.
CONCLUSIONS: The Paxos Scope produced images that can be reliably used to estimate vCDR, which closely aligned with the automated algorithm from OCT optic disc cube scan. The low cost, ready-to-integrate adapter, and minimal training requirements make it a viable option for population-based screening in low-resourced settings.
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