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Jason Turuwhenua, Mehrdad Sangi, Benjamin Thompson; Objective optokinetic nystagmus measurement in children from consumer grade video. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2912.
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© ARVO (1962-2015); The Authors (2016-present)
Accurate clinical assessment of visual function in young children is challenging. Optokinetic Nystagmus (OKN) may allow for objective measurement of visual function in children if appropriate child-friendly eye tracking techniques are available.
We developed software tools to analyze video footage of children (n = 5 children, n = 20 individual trials) freely viewing dynamic random dot stimuli designed to elicit OKN (250 dots, 0.5° diameter, drifting at 8°/second). The videos were recorded using an off-the-shelf video recorder (SONY digital high definition camera HDRCX7EK, Sony Corporation, Tokyo, Japan). A novel head stabilization technique based on tracking random features of the face was applied to the videos to obtain a stable visualization of the head area. This was followed by extraction of the eye velocity in the stabilized eye region. Finally, the presence of OKN was detected using a method in which quick phases fitting heuristic criteria were averaged and thresholded. The outputs of our technique were compared with the observations of two observers masked to the results of the method. Firstly, the quick phases observed by an experienced observer were compared to those detected by the automated method. Secondly, the overall computer determined assessment as to the presence of OKN in each trial was compared with judgements made by a clinical assessor.
The sensitivity and specificity of our eye movement detection was 89.1% and 98.9% respectively across all trials, with an experienced observer as a baseline. The positive predictive and negative predictive values were 72.6% and 99.5% respectively. Our OKN detection method predicted the clinical assesor's results in 17 of 20 (85%) of the trials.
We developed tools that improved the visualization of the eye, and facilitated the measurement of OKN related eye movements from videos of children. The results suggest that consumer grade equipment can be used for the assessment of eye movements in children, which may help in the diagnosis of visual disorders.
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