title: Similar contrast sensitivity functions measured using psychophysics and optokinetic nystagmus.
abstract: Although the contrast sensitivity function (CSF) is a particularly useful way of characterising functional vision, its measurement relies on observers making reliable perceptual reports. Such procedures can be challenging when testing children. Here we describe a system for measuring the CSF using an automated analysis of optokinetic nystagmus (OKN); an involuntary oscillatory eye movement made in response to drifting stimuli, here spatial-frequency (SF) band-pass noise. Quantifying the strength of OKN in the stimulus direction allows us to estimate contrast sensitivity across a range of SFs. We compared the CSFs of 30 observers with normal vision measured using both OKN and perceptual report. The approaches yield near-identical CSFs (mean R = 0.95) that capture subtle intra-observer variations in visual acuity and contrast sensitivity (both R = 0.84, p < 0.0001). Trial-by-trial analysis reveals high correlation between OKN and perceptual report, a signature of a common neural mechanism for determining stimulus direction. We also observe conditions where OKN and report are significantly decorrelated as a result of a minority of observers experiencing direction-reversals that are not reflected by OKN. We conclude that there are a wide range of stimulus conditions for which OKN can provide a valid alternative means of measuring of the CSF.
authors.affiliation: School of Optometry &Vision Science, The University of Auckland, New Zealand.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Dakin
authors.affiliation: School of Optometry &Vision Science, The University of Auckland, New Zealand.
authors.forename: Philip R K
authors.initials: PR
authors.lastname: Turnbull
mesh_terms: D000293:Adolescent; D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D017120:Nystagmus, Optokinetic / Q000502:physiology*; D011601:Psychophysics