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Jack Phu, Henrietta Wang, Michael Kalloniatis, Sieu Khuu; Statokinetic dissociation in anterior visual pathway disease is eliminated by equating the psychophysical procedures. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1270.
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© ARVO (1962-2015); The Authors (2016-present)
Sensitivity to kinetic and static stimuli has been assumed to be different in visual field (VF) assessment, i.e. statokinetic dissociation (SKD). We have recently demonstrated that SKD can be eliminated in normal observers by removing criterion bias introduced by Method of Limits (MoL) in kinetic perimetry (Phu et al., 2017 JoV). Here, we test the hypothesis that SKD previously reported in anterior visual pathway disease, is also eliminated by equating the psychophysical procedure and removing criterion bias.
We tested six patients with retinitis pigmentosa (RP), six patients with early open-angle glaucoma (OAG) and six normal observers. The first phase of testing used two-way MoL to establish the isocontrast region (ICR) described by kinetic perimetry. This was compared with static perimetry sensitivity to determine if SKD existed. In the second phase, Method of Constant Stimuli (MoCS) and a two-interval forced choice (2IFC) procedure were used to present stimuli at levels of eccentricity around the ICR found in phase one. Observers were tasked to detect static or kinetic (in towards or outward from fixation) stimuli. Psychometric functions were fit to determine the difference in threshold eccentricity for stimulus detection.
RP and POAG patients had ICR different widths at the boundary of clinical VF deficit, depending on individual criterion bias. In normal subjects, the width of the blind spot also differed to measurements made on fundus photography. Once MoCS and 2IFC procedures were used, there were no differences in threshold eccentricity for static and kinetic stimuli conditions for RP or OAG patients (Fig A and B). The blind spot of normal observers was also more accurately delineated (Fig C).
SKD in patients with RP and OAG, and at the physiological blind spot is eliminated when the psychophysical procedure is equated. Methods without criterion bias may provide a more accurate representation of the VF.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Psychometric functions for regions of VF deficit for an OAG, RP and the blind spot region of a normal subject: proportion seen as a function of eccentricity (o) for static (black), inward (blue) and outward moving (red) stimuli. Gray zone indicates the ICR. Inset shows difference in threshold eccentricity for each pairwise comparison for the representative subjects (mean and SD shown, all not different to 0, p>0.05).
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