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Tanya Kowalski, Ehud Zamir; A Novel Smartphone-Based Method for Quantitative Estimation of the Anterior Chamber Depth. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5899.
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© ARVO (1962-2015); The Authors (2016-present)
We recently described the use of lateral photography as a simple, accurate method for quantitative anterior chamber depth (ACD) estimation by calculating the relative anterior displacement of the pupil (E:Z ratio). Our purpose was to assess the accuracy of ACD estimation by emergency physicians using smartphone lateral eye photography and a standard photo set.
Lateral smartphone photographs and Scheimpflug photography ACD measurements of 10 random healthy eyes were taken for the study. A standard lateral photo set of 17 eyes with incremental ACDs between 1.6 mm and 3.2 mm was prepared. Forty emergency physicians were asked to estimate the E:Z ratio and the corresponding ACD in each of the photos by matching it to the standard photo set. The answers were compared to standard biometric true ACD of the study eyes.
There was a high degree of agreement between participants about the estimated ACD, with an intra-class coefficient of 0.92. The mean absolute estimation error and the standard deviation (SD) of the error in individual eyes ranged between 0.03 mm and 0.22 mm, and between 0.05 mm and 0.16 mm, respectively. The mean absolute estimate error across all 400 estimates was 0.13 mm, with a SD of 0.12 mm. The overall sensitivity and specificity of the test to detect an ACD of 2.5 mm or less were 0.93 and 0.94, respectively.
Smartphone lateral eye photography with matching of the image to a standard photo set is a rapid, simple and clinically useful method to assess the depth of the anterior chamber, which is an important diagnostic parameter when considering primary angle closure glaucoma.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
A lateral (temporal) perpendicular photograph of an eye with schematic outline of the photogrammetric method used to calculate the EZ ratio. The cross indicates the tangential limbus line (vertical, purple) and the limbus-pupil-cornea line (horizontal, green). The three blue dots mark the cardinal points: Temporal limbal mark (L), mid pupil mark (P), and corneal mark (C). E, Lateral photographic temporal limbus to pupil distance; Z, Lateral photographic temporal limbus to cornea distance. The virtual ACD is Z-E.Taken from: Zamir E, Kong GY, Kowalski T, Coote M, Ang GS. A Novel Method of Quantitative Anterior Chamber Depth Estimation Using Temporal Perpendicular Digital Photography. Transl Vis Sci Technol. 2016;5(4):10. Figure 2.
Using the EZ ratio to estimate ACD: a standard photo set.
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