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Paul Alan Harris, Torrie Garner, Mehrdad Sangi, Peng Guo, Jason Turuwhenua, Ben Thompson; Visual acuity assessment in adults using optokinetic nystagmus. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5907.
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Visual acuity assessment is extremely challenging in non-verbal populations. We assessed the level of agreement between three monocular visual acuity measures: a novel optokinetic nystagmus (OKN) induction and assessment instrument that required no verbal or subjective response, an Automated ETDRS (A-ETDRS) chart and a Harris visual acuity chart.
Monocular visual acuity (VA) data for 20 uncorrected neurotypical adults (mean age 25 yrs) are reported in logMAR. During the OKN-based test, subjects with uncorrected monocular vision viewed an array of drifting (left/right,) vanishing optotypes from a distance of three meters. Optotypes were constructed from an outer dark annulus and an inner light circle presented on a grey background. Stroke width varied from 0.0 to 1.0 logMAR to measure acuity thresholds. A prototype device (Objective Acuity Ltd. Auckland, New Zealand) displayed the stimuli and recorded eye movements for offline analysis, which included detection and tracking of the face and pupil center along eye displacement and velocity estimation. Monocular VA was also measured with an A-ETDRS system from three meters, and the Harris Visual Acuity Chart from six meters (M&S Technologies Chicago, Illinois).
A-ETDRS measurements ranged from -0.3-1.0. OKN VA thresholds were positively correlated with A-ETDRS measurements (R2 = 0.93). The A-ETDRS and Harris Visual Acuity measurements were also positively correlated (R2 = 0.94).
OKN induction and measurement has the potential to provide an objective visual acuity test for use in all clinic populations, including where verbal communication and/or English alphabet letter recognition is limited due to language barriers or abnormal neurodevelopment. Further development of the OKN-based visual acuity measurement technique is justified based on these promising initial results.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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