Automated visual acuity estimation by optokinetic nystagmus using a stepped sweep stimulus

Area of Science:

• Ophthalmology
• Neuroscience
• Biomedical Engineering

Background:

• Visual acuity (VA) measurement is crucial for eye health assessment.
• Current methods may be challenging for certain patient populations.
• Optokinetic nystagmus (OKN) offers a potential alternative for objective VA assessment.

Purpose of the Study:

• To introduce and evaluate an automated system for objective visual acuity measurement using optokinetic nystagmus (VA-OKN).
• To assess the sensitivity and specificity of the VA-OKN system in detecting reduced visual acuity in adults.
• To compare the performance of VA-OKN with the established Early Treatment of Diabetic Retinopathy Study (ETDRS) chart (VA-ETDRS).

Main Methods:

• Adults with normal (n=12) and reduced (n=11) VA (VA-ETDRS > 0.20 logMAR) underwent monocular VA-OKN measurements.
• An automated system presented drifting vanishing discs of varying sizes (0.00-1.00 logMAR) to elicit OKN.
• Eye-tracking data identified the onset/cessation of OKN to determine VA-OKN, averaged across multiple sweeps.

Main Results:

• The VA-OKN system demonstrated 100% sensitivity and specificity in detecting reduced VA at the 0.20 logMAR threshold.
• No significant difference was found between VA-OKN and VA-ETDRS measurements (p=0.55).
• Strong correlation and agreement were observed between VA-OKN and VA-ETDRS (r²=0.84, ICC=0.90).

Conclusions:

• Automated VA-OKN effectively identifies visual acuity deficits in adults.
• VA-OKN is a reliable and objective method, strongly correlating with the gold-standard VA-ETDRS.
• The VA-OKN system shows potential for assessing visual acuity in cognitively impaired adults and pre-verbal children.