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Oren Yehezkel, Abraham Spierer, Dan Oz, Ran Yam, Michael Belkin; A method for rapid objective strabismus angle measurement. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2931. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Evaluation of the accuracy and repeatability of a novel strabismus angle measurement method using an automatic objective system based on eye tracking, in comparison with the prism cover test(PCT). The angle of strabismus is conventionally measured by the PCT in which prisms of increasing powers are placed in front of the eyes to neutralize the eye movement elicited by alternately covering one eye. The PCT methodis subjective, time consuming, very difficult to perform on babies, and young children and relies heavily on the examiner’s skill and experience. The novel method being tested may constitute a replacement to the PCT.
The concept being tested is similar to the PCT principle using a system comprising of a 3D display and glasses. Instead of shifting the line-of sight of the deviating eye by using prisms while gazing at a single target, the system displays alternately 2 moving dichoptic targets on a screen until the line-of-sight of each eye coincide with its corresponding target. An eye tracker is used in order to detect cessation of eye movements when both eyes fixate at their targets. No eye tracker calibration is required to perform the test. The strabismic prism diopter deviation is automatically calculated from the distance between the two dichoptic targets and the distance of the eyes from the display. Tests were conducted under normal room lighting at 60 cm. Two groups are being tested: One consisting of healthy people with artificially induced quantified eye deviation created by placing a prism in front of one of the subject’s eye (N=4, average age 52±13 years). The second group includes strabismic subjects, who are evaluated in comparison with PCT (N=4, average age 25±19 years).
The measurements of the healthy group with induced strabismus, are accurate and repeatable, while placing8 diopter prism lens in front of one eye the measured deviation was 7.8±0.32 (SD) prism diopter and the maximal SD for each subject repeated measurement was 0.15 prisms. Test duration was 7.6±3.6 (SD) seconds. Test results of the strabismic group measured were 28.4±17.8 (SD) for the eye tracking method and comparable to the cover test results of 29.2±18.5 (SD). Test duration of the novel method was 23±11.6 (SD) seconds.
The preliminary results of this work in progress indicate the possible validity of the concept of measuring strabismus angles by a system based on a 3D screen and an eye tracking module.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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