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Shrinivas Pundlik, Matteo Tomasi, Kevin Houston, Gang Luo; Preliminary Evaluation of a Mobile App for Strabismus Screening. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5212.
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© ARVO (1962-2015); The Authors (2016-present)
An automated Hirschberg Test using photographic analysis of the corneal reflection has been suggested as a method to screen for strabismus. However, cost to develop and maintain a dedicated device can hinder accessibility. Smartphones offer a platform to dispense inexpensive and widely accessible eye-care solutions. We have developed a mobile app with the goals of obtaining rapid, convenient, and quantifiable strabismus measurements. We present the results of a preliminary evaluation experiment to determine the accuracy of the app.
When using the app, an examiner asks the patient to fixate at a particular point and simply points the phone camera to the patient's face. Real time eye detection is shown on the screen, after which a snapshot can be taken with the flash on. The app then localizes the iris center, the corneal reflection, and computes the eye deviation according to the offset of the corneal reflection from the iris center. To evaluate the accuracy of the app, four subjects without strabismus fixated binocularly at 11 points at various eccentricities from -5.8° to 5.8° (a total of about 20Δ range). Eye deviations with respect to the center point (0°) were computed for the left and right eyes separately, and compared with the ground truth. In a case study, one subject with known left exotropia was tested with the cover test and by the app. In this case, the app measured the difference in the deviations of the two eyes.
The app measurements for the 8 eyes closely matched the ground truth, with a slight over estimation (line fitting slope=1.08, R2=0.99). The mean measurement error was 1.1 ± 0.9Δ.There was no difference between right and left eyes (p=0.18). In case of the patient with known strabismus, the cover test and the app found left exotropia of 24 ± 3.6Δ and 28.5 ± 3.5Δ, respectively.
Preliminary results indicate that the strabismus app can accurately measure a wide range eye deviations and further clinical testing of the app is warranted.
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