Trefford L. Simpson's research while affiliated with University of Waterloo and other places

Publications (12)

Article
Full-text available
Purpose: To evaluate the detectability of pneumatic corneal stimuli and response bias using multi-stimuli multi-criterion signal detection theory (MSDT). Methods: Thirty-six participants were recruited using convenience sampling. A Waterloo Belmonte esthesiometer was used to deliver cold, mechanical, and chemical stimuli to the center of the cornea...
Article
Full-text available
Purpose: To evaluate the feasibility of using signal detection theory (SDT) in estimating criterion and detectability indices for corneal pneumatic stimuli and test corneal psychophysical data against linking hypotheses from nonprimate physiology using Bayesian analysis. Methods: Corneal pneumatic stimuli were delivered using the Waterloo Belmon...
Article
Full-text available
Purpose Ocular somatosensory-autonomic reflexes play critical roles in maintaining homeostasis of the eye. The purpose of this study was to investigate the pupil response to nociceptive corneal stimuli. Methods A Waterloo-Belmonte pneumatic esthesiometer was used to determine detection thresholds and randomly deliver mechanical and chemical stimul...
Article
Full-text available
Purpose: To use a human-based model to study the effects of repeated tear film instability on corneal detection thresholds to cold, mechanical, and chemical stimuli. Methods: Twenty-five subjects participated in three study visits. A computer-controlled Belmonte esthesiometer was used to estimate corneal detection thresholds to cold, mechanical,...
Article
Full-text available
Purpose: To determine the feasibility of using a portable carbon dioxide (CO2) sensor to calibrate a pneumatic esthesiometer and then to calibrate the chemical stimuli. Methods: The chemical stimuli in ocular surface experiments are combinations of medical air and added CO2 (%CO2). These stimuli were calibrated using a portable CO2 sensor (COZIR...
Article
Full-text available
Purpose: To investigate the effects of tear film instability (TFI) induced by sustained tear exposure (STARE) on sensory responses to corneal cold, mechanical, and chemical stimuli. Methods: Fifteen normal subjects were enrolled. TFI was induced during 10 repeated trials of STARE. Pneumatic cold, mechanical, and chemical stimuli were delivered u...
Article
Significance: The conjunctiva is an integral component of the ocular surface, and its vasculature forms a terminal vascular bed of the human internal carotid artery. No research on the response of conjunctival vasculature to ocular surface stimulation exists; however, it is essential to understand the local physiological and pathological responses...
Article
Purpose: To model between subject variability of corneal swelling (CS) and deswelling after overnight wear of silicone hydrogel (SiHy) contact lenses. Methods: A total of 29 neophyte subjects wore 12 SiHy lenses with central transmissibility range of 31 to 211 Dk/t units on separate nights, in random order, and on one eye only. The contralateral...
Article
Purpose: In many sports, athletes rely on visual information from the environment to perform. Some literature suggests athletes have superior visual abilities to non-athletes, particularly on tasks representative of the visual demands of their sport, such as dynamic acuity, eye movement accuracy and speed, and peripheral vision. Other literature s...
Article
Purpose: To evaluate the influence of blur on ocular comfort while systematically manipulating vision using habitual refractive correction, induced spatial blur, dioptric defocus, and under the absence of visual structure. Methods: Twenty emmetropic subjects rated vision, ocular comfort, and other sensations (burning, itching, and warmth) under...

Citations

... The cold thermo-receptors and polymodal nociceptors transduce signals conducted through the C-fibers, while the mechanonociceptors transduce information for the fast-conducting Aδfibers' rapid response to painful mechanical stimuli (MacIver and Tanelian, 1993a;MacIver and Tanelian, 1993b;Belmonte et al., 2004). Since there is no systematic neurophysiological examination on the effects of human corneal stimulations, the presence of receptors/channels in the human cornea has been evaluated psychophysically (Feng and Simpson, 2004;Jayakumar and Simpson, 2020). Feng and Simpson (2004) have identified multiple corneal psychophysical channels in the human cornea. ...
... There were several results indicating the internal validity of the data we found. Although this paper is primarily about the feasibility of signal detectability (and in signal detection theory, "thresholds" do not exist), the detection thresholds (used in deriving stimulus intensities for the MSDT experiments) obtained in this study were consistent with previous studies that measured corneal detection thresholds as a primary outcome measure (Feng and Simpson, 2003;Situ et al., 2008;BasuthkarSundarRao and Simpson, 2014;Jayakumar et al., 2015;Alabi and Simpson, 2020). In addition, the MSDT data for pneumatic stimuli used in this study followed the assumptions of SDT, which were evident in the ROC curves and Gaussian distributions reported in the results (Figures 4, 6, 8). ...
... A large, more recent study showed heterogeneity in corneal mechanical sensitivity in DED patients : 13% of cases had reduced mechanical thresholds (hyperesthesia) that were associated with worse symptoms and 10% of cases had increased mechanical thresholds (hypoesthesia) that were associated with worse corneal epitheliopathy. Also of note is the fact that sustained tear instability in normal subjects affects corneal sensitivity to different modalities: sensitivity decreases with cold stimulation but increases with mechanical and chemical stimuli; this effect lasts for at least 30 min (Awisi-Gyau et al., 2019;Situ et al., 2019). Thus, the rapid adaptive capacity of corneal nerves to changing environmental conditions could also confound measurements. ...
... Since other ocular MSDT studies are not available for comparison within the ocular somatosensory system, the human response to similarly scaled stimulation might need to be examined indirectly. Alabi and Simpson (Alabi, 2018;Alabi and Simpson, 2019;Alabi and Simpson, 2020) observed a dose-effect increase in the autonomic responses such as redness, pupillary response, and accommodation for pneumatic stimuli. Situ et al. (Situ and Simpson, 2010) also reported an increase in the tearing response (using tear meniscus height measurement) and these taken together point to similar monotonic scaling of the human psychophysiological response to painful and cooling corneal stimulation. ...
... A large, more recent study showed heterogeneity in corneal mechanical sensitivity in DED patients : 13% of cases had reduced mechanical thresholds (hyperesthesia) that were associated with worse symptoms and 10% of cases had increased mechanical thresholds (hypoesthesia) that were associated with worse corneal epitheliopathy. Also of note is the fact that sustained tear instability in normal subjects affects corneal sensitivity to different modalities: sensitivity decreases with cold stimulation but increases with mechanical and chemical stimuli; this effect lasts for at least 30 min (Awisi-Gyau et al., 2019;Situ et al., 2019). Thus, the rapid adaptive capacity of corneal nerves to changing environmental conditions could also confound measurements. ...
... The same is true with SiHy lenses. Although, on average, the risk of corneal vascularisation has been minimised with greater oxygen availability in SiHy lenses [125,404,405], a cautious approach to identify and monitor high-swellers is still suggested [406][407][408]. This is to prevent potentially sight-threatening outcomes from silent vessel ingrowth, as well as to lower the risk of possible inflammatory events associated with vascularisation in these patients [409]. ...
... In order to address the limitations found in the scientific literature, the aim of this study was to assess the acute effects of caffeine ingestion on DVA. To do so, DVA was measured with a recently developed and validated test (moV&; V&MP Vision Suite) (Hirano et al. 2017) before and after the ingestion of a capsule of 4 mg/kg of caffeine or placebo on two different days in a randomized order. Complementarily, we obtained the perceived levels of activation in order to check the effectiveness of caffeine/placebo manipulation. ...
... 123 Finally, vision quality should not be overlooked. An association between clarity of vision and ocular comfort in non-CL wearers has been reported, 124 and greater ocular comfort scores were associated with higher subjective vision quality in subjects corrected with soft toric CLs. 125 Contemporary thinking about how to address CLD continues to evolve over time. ...
... Conversely, a study on daily wearers of hydrogel, SiHy or rigid corneal contact lenses failed to demonstrate an effect of lens type on upper lid wiper staining [263]. In addition, a number of studies showed no significant differences in LWE grades or patterns between SiHy lens types [254,260,264]. In contrast, in a study of a large sample of soft contact lens wearers, habitual senofilcon A wearers were found to have the lowest LWE grades. ...