Quantitative visual acuity measurement in young children using tablet-based optokinetic nystagmus videography

Abstract

Purpose : Quantitative measurement of visual acuity in young children can be challenging, but is important for detecting early childhood vision abnormalities. Optokinetic nystagmus (OKN) is present in very young children. The purpose of this pilot study is to demonstrate the feasibility of a custom software app (Vifant OKN) using a consumer-grade tablet computer for quantitative assessment of resolution acuity by OKN in young children.

Methods : Nine children with normal eye exams and normal visual development, from 9 to 40 months of age (mean 17.6 months), were tested with the Vifant OKN app binocularly and then monocularly. The visual target consisted of black and white gratings varying in 5 increments from 0.2 - 2.4 cycles per degree (CPD), at a rate of 10 degrees per second at 44 cm. The gratings were presented for 3 seconds each, sequentially from lowest to highest frequency with a short animation presented between each increment to help maintain attention.
Trained video image readers graded videos taken from each testing period, counting the number of pursuit and saccadic eye movements, blinks, head movements and inattention.

Results : All 9 subjects demonstrated gradable binocular and monocular eye movements. Eight of 9 subjects binocularly and 5 of 9 monocularly demonstrated pursuit and saccadic movements at the highest frequency measured (2.4 CPD). Blinks and head movements were similar in binocular and monocular tests and did not interfere with detection of saccadic or pursuit movements. Inattention was more frequent with monocular testing.

Conclusions : Quantitative measurement of resolution visual acuity in young children with OKN response is feasible using a consumer-grade tablet computer and a custom app (Vifant OKN), with trained graders interpretation of video recordings of eye movements. OKN responses are detected with 3 second intervals of kinetic gratings under both binocular and monocular conditions. Inattention was more frequent with monocular testing, and maximal resolution was better with binocular testing.
Incorporation of automated eye tracking may allow automated, real-time visual acuity measurement in pre-verbal and verbal young children.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.