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Michael Joseph Fliotsos, Jasmine Jalali, Olivia Dryjski, Allen O Eghrari; Validation of Smartphone Specular Microscopy: A new tool for endothelial cell analysis in resource-limited settings. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5728. doi: https://doi.org/.
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Specular microscopy provides a magnified view of the corneal endothelium for assessment and management of corneal disease. However, cost and size limit the use of specular microscopes in resource-limited settings. We sought to validate a method to assess corneal endothelial cell density (ECD) using a smartphone and slit-lamp biomicroscope at a fraction of the cost of traditional specular microscopy.
The study was approved by the Johns Hopkins Medicine Institutional Review Board. Healthy volunteers (n=6) without known ocular comorbidity were recruited for this study. The light beam on a TopCon photo slit-lamp biomicroscope was reduced to 0.2 mm diameter, set to maximum brightness, and directed toward the cornea at an angle to achieve specular reflection. Using an iPhone 7 Plus on video mode, held to the slit-lamp which was set at 40X zoom, we recorded videos of the endothelial cell layer. A frame was captured and the number of cells counted. This process was repeated for the second eye. Images were also captured using a Konan CellChek specular microscope for each eye, from which we calculated ECD from at least 60 contiguous cells using the flex-center method. To validate the smartphone technique, the area of the slit-lamp beam was calculated from the right eye image by dividing the number of cells in the smartphone image by the ECD calculated from the specular microscope to estimate the total illuminated area in the smartphone image of the right eye. Then, using this calculated area from the right eye, the smartphone ECD was predicted in the left eye based on the total count and compared with the specular microscopy measurement from the left eye.
Six participants underwent ophthalmic imaging. The average video length was 2:37 minutes (range: 0:28 to 5:27). Images were acquired from 12 out of 12 videos successfully. In one individual, the specular microscope was unable to capture an image with at least 60 cells and data was excluded from analysis. Among 5 participants, the difference between smartphone ECD and specular microscopy ECD was 2.7%, 6.2%, 6.7%, 12.7%, and 43.5%, resulting in a strong correlation (r = 0.859).
We demonstrate the ability to effectively visualize and analyze the corneal endothelium using a smartphone and slit lamp biomicroscope.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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