Predicting Letter Acuity Using Vernier-Induced OKN and Consumer-Grade Cameras

Area of Science:

• Ophthalmology
• Neuroscience
• Vision Science

Background:

• Optokinetic nystagmus (OKN) is a valuable tool for objective visual acuity assessment.
• Precise OKN quantification for visual acuity typically requires specialized eye-tracking equipment.
• Current methods face challenges in accessibility and cost-effectiveness.

Purpose of the Study:

• To establish an optimized method for visual acuity measurement using OKN induced by vernier acuity.
• To assess the correlation between this novel OKN-based method and subjective letter acuity.
• To evaluate the feasibility of using both research-grade and consumer-grade eye trackers.

Main Methods:

• Thirty-nine adults underwent monocular visual acuity testing.
• Stimuli with varying vernier offsets were presented horizontally to induce OKN.
• Eye movements were recorded using both research-grade eye trackers and a consumer-grade USB camera.
• An automated algorithm quantified OKN responses and calculated a relative OKN index.

Main Results:

• Strong correlations were found between subjective letter acuity and the relative OKN index (r=0.82 with eye tracker, r=0.76 with USB camera).
• The method demonstrated high accuracy in predicting letter acuity with low mean absolute errors (0.15 and 0.16 logMAR).
• High accuracy (AUC values of 0.97 and 0.95) was achieved in identifying participants with reduced visual acuity.

Conclusions:

• This study provides proof-of-concept for OKN-based vernier acuity measurement in adults.
• The method shows promise for visual acuity assessment with or without advanced eye-tracking technology.
• Future research is needed to investigate its application in pediatric populations.