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Anna Kosovicheva, Melanie Kazlas, David G Hunter, Peter Bex; What can we learn about strabismus from a 90 second gaze recording?: Rapid evaluation of oculomotor deficits in strabismus. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2929. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Clinical evaluation of ocular alignment can be performed with a variety of assessments, including ocular imaging and prism cover tests. However, obtaining precise strabismus measurements with these procedures at a range of gaze postures can require skill or be time-consuming. The purpose of this study was to test the feasibility of using readily available eye tracking equipment for this purpose. We developed and tested a rapid eye tracking based procedure for evaluating ocular alignment and oculomotor deficits in strabismus.
Gaze position was recorded binocularly using an eye tracker in a total of 11 observers (7 strabismic subjects, including 4 with amblyopia, and 4 controls, ages 7 – 50). Subjects were instructed to track a crosshair target that moved between locations on an invisible grid spanning 18° vertically and 24° horizontally for a total gaze recording time of approximately 90 seconds. At each location, subjects viewed the target monocularly for 1000 ms through a pair of shutter glasses. Halfway through each interval, the presentation of the target switched between the two eyes, producing a measurement of differences in gaze position between left eye and right eye targets. In addition, on half the trials, the target remained in the same eye, allowing for a longer measurement of fixation stability for monocular targets.
For pairs of monocular targets presented in the same physical location, we observed larger differences in gaze position between left and right eye targets in strabismic subjects (2.84° ± 0.62°) than controls (0.27° ± 0.05°), p = .014. For strabismic subjects, the angular shift in gaze position between pairs of targets correlated with the errors made in an independent dichoptic alignment task (Spearman’s r = 0.82, p = .034). Subjects with strabismic amblyopia additionally showed reduced fixation stability while viewing targets presented to the fellow eye (larger BCEA in the amblyopic compared to fellow eye, p = .010).
Together, our results demonstrate that assessment of ocular alignment at a range of gaze postures can be quickly performed using an eye tracking procedure, and that strabismus measurements from this objective gaze recording method show good agreement with subjective measures based on perceptual alignment.
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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