Abstract
PurposeThe aim of the current study was to develop and validate an automated contrast sensitivity (CS) test using a live- detection of optokinetic nystagmus (OKN) and an adaptive psychometric procedure. In addition, the study sought to replicate the known effect of defocus on CS for the OKN-based measurements in emmetropic participants.MethodsFifteen participants viewed a horizontally moving grating while their eyes were tracked with an infra-red (IR) eye-tracker. To simulate the clinical conditions of the CS measurements, the participants were stimulated monocularly as the left eye was occluded by an IR filter. The horizontal eye position was continuously analyzed for OKN responses, and the stimulus contrast was changed by an adaptive psychometric method depending on the outcome. Furthermore, the newly proposed OKN live-detection was verified against an offline analysis and an expert-observer judgement. The OKN-based CS was measured for six spatial frequencies at normal vision and three levels of defocus using spherical convex lenses.ResultsThe newly proposed OKN live-detection method showed a sufficient detection performance for implementation of adaptive procedures, and the detection rate is similar or better compared to offline detection methods. Spatial frequency and defocus had a significant effect on the OKN-based CS (P < 0.0001 for both).ConclusionsThe current study presents a novel method to measure motion CS in an automated way, combining the real-time detection of OKN and an adaptive psychometric procedure. Furthermore, the known effect of defocus on CS was successfully replicated with the newly developed tool.Translational RelevanceOKN-based CS is a novel approach to assess spatial vision, which is sensitive to subtle effects of defocus, allowing use with nonverbal patients and infants. Furthermore, the newly developed tool may improve the performance of such measurements.
Highlights
Assessment of contrast sensitivity (CS) from eye movements has already been proposed as a possible method to gain objective information
Translational Relevance: optokinetic nystagmus (OKN)-based CS is a novel approach to assess spatial vision, which is sensitive to subtle effects of defocus, allowing use with nonverbal patients and infants
The current study considered the implementation of an adaptive psychometric algorithm as an efficient method to estimate CS from OKN in real time
Summary
Assessment of contrast sensitivity (CS) from eye movements has already been proposed as a possible method to gain objective information These measurements may help examine noncommunicative participants.[1] Previous research has shown that in objective testing of CS, several types of eye movements can be implemented, namely microsaccades[2,3,4] or smooth pursuit eye movements.[1] In addition, the eye movement occurring in response to a moving scenario, optokinetic nystagmus (OKN), has been linked to the appraisal of CS (motion CS).[5,6,7] Canonically, OKN is a saw-tooth displacement of the eye, denoting the two phases of the OKN. The slow phase (OKN-SP) identifies a motion-tracking eye movement occurring in the direction of the visual stimulus drift. This phase is similar in nature to smooth pursuit eye movements, because largely overlapping neural circuitry was found
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