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Trefford L Simpson, Nancy J Keir, William Ngo, Yunwei Feng; Using corneal chemical detection thresholds to select subjects for ocular surface discrimination sensory panels.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3884.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if we can we select sensitive (‘good’) and less sensitive (‘bad’) participants in a sensory panel examining interocular judgments of contact lens comfort, using Belmonte esthesiometry.
49 subjects (adapted contact lens wearers) had chemical detection thresholds (% added CO2) measured with the Waterloo Belmonte Esthesiometer, on 3 occasions (at least a day apart), using the ascending method of limits. From the averages of these 3 measurements, 25 subjects were grouped as more sensitive (thresholds at or below median) or less sensitive (thresholds above median). Subjects also interocularly matched the discomfort of 3 optimally fit contact lenses using the mechanical or chemical stimuli of the esthesiometer and scaled discomfort using magnitude estimation. We tested a simple hypothesis: Subjects in the sensitive group would be better at interocular matching - regression pneumatic stimulus match to rated discomfort would be linear with a positive slope, but the control group would not perform well, with random slopes (positive, 0 and negative). Bayesian mixed modeling (with vague priors) estimated the group slopes (among others) and the distributions of these estimates were compared in the sensitive and control groups defined by chemical detection thresholds. R and rjags were used for the data analysis.
For the ‘bad’ group the regression slopes mode was 0.05 and the 95% HDI was -0.526-0.731. The figure (of the posterior distribution of the slope estimates) shows that for the ‘good’ group the mode was shifted and the 95% HDI did NOT include zero.
Chemical thresholds can be used to separate sensitive and insensitive subjects who can match contact lens discomfort in a ‘well behaved’ way and therefore pneumatic esthesiometry may be used to select sensory panels.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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