Qualitative and Quantitative Analysis of the Corneal Endothelium With Smartphone Specular Microscopy

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Abstract
Purpose: We sought to demonstrate the feasibility of a lower-cost, portable method for qualitative and quantitative analysis of the corneal endothelium using a smartphone and slit-lamp biomicroscope. Methods: In this study, at a single academic center, we recruited healthy participants to undergo imaging of the corneal endothelium using both a smartphone-based method and a specular microscope. Participants first had their eyes imaged with a CellChek NSP-9900 Specular Microscope (Konan Medical, Inc, Irvine, CA). For image capture on the smartphone, a beam of light approximately 0.2 mm in diameter was directed to the center of the cornea with a slit-lamp biomicroscope to achieve specular reflection. With 40× zoom on the slit-lamp and 4K video mode set on an iPhone 7 Plus held to an ocular, the corneal endothelium was recorded until the hexagonal pattern of cells was identified and the sharpest frame from the video was selected. Results: The videos were analyzed from 14 sets of eyes (average length 2 minutes 40 seconds). The average intraclass correlation coefficient was 0.67 (95% confidence interval, 0.43–0.82). The mean difference between smartphone endothelial cell count and specular endothelial cell count was −209 cells/mm2 (SD = 483 cells/mm2), which did not achieve significance (P = 0.14). A Bland–Altman analysis with simple linear regression showed no proportional bias when comparing the 2 modalities (coefficient = −0.20; t-value = −0.42; P = 0.68). Conclusions: Smartphone specular microscopy is capable of qualitative and quantitative analysis of the corneal endothelium. Further refinement to standardize the light source and automate analysis will increase feasibility.

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