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Deborah Antwi, Carolyn G Begley, Ping Situ, Trefford L Simpson; Changes in corneal mechanical, chemical and cold thresholds following repeated tear film instability. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4904.
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© ARVO (1962-2015); The Authors (2016-present)
To determine whether corneal thresholds to cold, mechanical and chemical stimuli are altered following tear film instability (TFI).
Detection thresholds and magnitude estimations to pneumatic cool, mechanical and chemical stimuli were measured using a computerized Belmonte esthesiometer for 25 subjects. Measurements were done before (B), immediately after (A) and 30 minutes after (30A) after subjects completed 10 consecutive sustained tear exposure (STARE) trials which induced TFI by keeping the tested eye open as long as possible. Subjects also completed a Current Symptom Questionnaire (CSQ) after threshold measurement at B, A, and 30A time periods. Repeated measures ANOVA with Bonferroni correction was used to determine significant differences between threshold measures at different time periods.
Mechanical thresholds (mean ± SE) were 82.70 ±7.48 at B, 67.53±5.95 at A, and 58.47 ±3.83 at 30A. Cool thresholds were 61.20 ± 4.94 at B, 58.73 ± 4.54 at A and 52.40 ± 3.77 at 30A. Chemical thresholds were 39.53 ± 4.25 at B, 40.27 ± 3.95 at A and 41.40 ± 3.49 at 30A. There was a significant difference between mechanical thresholds (p<0.001); B was significantly higher than A and 30A (p=0.047 and p<0.001 respectively). Although cool thresholds between times did not reach statistical significant level (p=0.057), there was a decreasing trend with eleven subjects becoming more sensitive on cool thresholds after STARE. There was no significant difference in chemical thresholds between the different time periods (p=0.565). CSQ scores (mean ± SE) significantly increased (p<0.001) immediately after STARE for both visits from 1.96±1.05 at B to 15.92±2.14 at A and 5.16±1.26 at 30A.
Mechanical and cold thresholds changed following repeated TFI stimulation, which could persist until 30minutes later. Although the exact events occurring during TFI are unknown, these results suggest that evaporation (cold receptors) and/or surface deformation or spikes in hyperosmolarity (polymodal nociceptors and cold receptors) may play a role in the increased CSQ scores in this study.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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