January 14, 2020
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Smartphone tonometer provides reliable preliminary IOP

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Calculating preliminary IOP using a smartphone-based tonometer yielded similar results compared with other tonometers, according to findings published in the British Journal of Ophthalmology.

Yue Wu and colleagues compared IOP measurements taken with a prototype smartphone tonometer with other tonometers used in clinical practice.

“As smartphones have become increasingly ubiquitous, a number of software programs and hardware attachments have been developed to allow a smartphone to perform various parts of the eye examination,” Wu, a graduate student at the University of Washington, and colleagues wrote. “Smartphone-based methods for measuring visual acuity have been validated.”

The researchers analyzed data from 92 eyes in 81 academic glaucoma patients. Measurements taken by Goldmann applanation tonometry (GAT) as well as ICare, pneumotonometry and Tono-Pen (Reichert) were compared.

The mean difference in IOP measurements was 0.24 mm Hg for GAT, -1.39 mm Hg for ICare, -3.71 mm Hg for pneumonotomy and -1.30 mm Hg for Tono-Pen, according to the study. The 95% limits of agreement were -4.35 mm Hg to 4.83 mm Hg for GAT, -6.48 mm Hg to 3.70 mm Hg for ICare, -7.66 mm Hg to -0.15 mm Hg for pneumotonometry and -5.72 mm Hg to 3.12 mm Hg for Tono-Pen.

The smartphone tonometer results were most consistent with GAT (R2 = 0.67; P < .001). Of the videos of the 92 eyes, 97.8% were within ±5 mm Hg of GAT, and 63% were within ±2 mm Hg of GAT, the authors wrote.

“A smartphone-based tonometer complements other existing smartphone hardware attachments and apps to facilitate a portable ophthalmological examination, which may improve access to ophthalmological care in resource-poor regions,” Wu and colleagues concluded. – by Earl Holland Jr.