Characterization of Optokinetic Nystagmus in Healthy Participants With a Novel Oculography Device.

Abstract

Objective: To develop a proof-of-concept smart-phone-based eye-tracking algorithm to assess non-pathologic optokinetic (OKN) nystagmus in healthy participants. Current videonystagmography (VNG) is typically restricted to in-office use, and advances in portable vestibular diagnostics would yield immense public health benefits.

Study design: Prospective cohort study.

Setting: Tertiary academic medical center.

Methods: Healthy participants (n = 39) without dizziness or vertigo were recruited. A smart-phone attached to a custom head stabilization device illuminated by a white LED circuit was used to record nystagmus induced with a 30 frames per second OKN stimulus over a 60-second period. A centroid tracking algorithm was created to detect slow-phase velocity (SPV) of horizontal nystagmus in a diverse subject cohort in a variety of lighting conditions. Nystagmus recordings were compared to those obtained with a standard VNG system.

Results: Non-pathologic nystagmus from an OKN stimulus was measured across multiple lighting conditions, with high signal-to-noise ratios (SNR) and mean SPV 22.13 ± 5.26°/s. Nystagmus SPV was not significantly different between the device and standard VNG system (t = -0.5, P = .6). Lighting conditions produced SNRs of 57.30 (ideal), 50.59 (backlit), 51.33 (side-lit), 49.28 (dark), 54.52 (outdoor lighting).

Conclusion: We demonstrate the feasibility of a novel portable oculography system in the detection of non-pathologic nystagmus in healthy subjects. Future applications of this system include: (1) to obtain real-time measurements of nystagmus during an acute vertigo attack; (2) to test patients unable or unwilling to present to a specialized vestibular laboratory; (3) to efficiently repeat testing overtime; (4) to improve accessibility of vestibular testing.