Multiple-criterion signal detection theory analysis of corneal pneumatic stimuli.

Abstract

Purpose : To evaluate the detectability (d_a) of pneumatic corneal stimuli and the response bias using a multi-stimuli multi-criterion signal detection theory (MSDT).

Methods : Thirty-six participants were recruited using convenience sampling and grouped based on contact lens use and symptoms score from the DEQ-5 questionnaire. A Waterloo Belmonte esthesiometer was used to deliver cold, mechanical, and chemical pneumatic stimuli to the corneal surface in three separate visits. The stimulus type was assigned randomly to each visit, and the threshold for the assigned stimulus type was obtained using the ascending method of limits, followed by the MSDT experiments to obtain d_a and bias. In the cold and mechanical MSDT experiments, 100 trials (80 signal (20 each for 4 intensities) and 20 catch trials) were presented in randomized order, and participants responded with a 5-point confidence rating to each stimulus. In the chemical MSDT experiments, 50 trials (20 signal trials each for two intensities and 10 catch trials) were presented, and responses were provided using 4-point confidence ratings. Detection theory estimates were obtained individually and as groups, which were then analyzed using mixed models and paired t-tests.

Results : d_a and the area under the curve (A_z) were significantly different between stimulus intensities within each stimulus type (all p<0.001), but were not different between stimulus types. Receiver operating characteristics (ROC) curves were clearly separable between stimulus intensities for all stimulus types, and no overlaps were observed in the z-ROC space. Bias calculated using the location of criterion (c), as expected, was significantly different between each psychophysical criterion level and between the intensities within a stimulus type (all p<0.001). For the chemical stimulus, c varied with stimulus intensity and was affected by group (asymptomatic/symptomatic, non-contact/contact lens wearers, and both, all interaction p<0.01). In addition, another bias metric, lnβ, depended on stimulus intensity and psychophysical criterion.

Conclusions : Using MSDT is feasible for analyzing ocular surface sensory processing and provides insight into the possible bias associated with the use of pneumatic stimuli. With noxious and non-noxious pnuematic stimulation, detectability and criteria vary systematically with stimulus intensity, a result that cannot be derived using classical psychophysics.

This is a 2020 ARVO Annual Meeting abstract.