Document Detail

Characteristics of human corneal psychophysical channels.
MedLine Citation:
PMID:  15326114     Owner:  NLM     Status:  MEDLINE    
PURPOSE: To characterize human corneal psychophysical channels. METHODS: Twenty subjects participated in this study. A Belmonte pneumatic esthesiometer was used to deliver stimuli, and the ascending method of limits and the method of constant stimuli were used to estimate thresholds. Sensation was characterized for different stimuli. Corneal mechanical and chemical thresholds were measured at different temperatures. RESULTS: The qualities of the sensations induced by stimuli with different temperatures were different, and the corresponding detection thresholds of the pneumatic stimuli at four temperatures gradually increased (repeated measures ANOVA (F(3,12) = 10.326, P = 0.000). There were no temperature effects on chemical thresholds (repeated measures ANOVA F(3,12) = 0.235, P = 0.870) or mechanical discomfort thresholds from 20 degrees C to 50 degrees C (paired t14 = -0.233, P = 0.818). There were strong interactions when chemical and mechanical stimuli were added. Chemical thresholds were progressively lower when the flow rate increased and mechanical thresholds went down as the percentage of added CO2 increased (repeated measures ANOVA F(3, 12) = 6.407, P = 0.007, F(4, 16) = 19.904, P = 0.000). CONCLUSIONS: This study suggests that humans sense corneal non-noxious cold and noxious mechanical and chemical stimuli, and that the sensitivity of some submodalities can be modulated by others. There are at least five psychophysical channels (non-noxious cold, noxious mechanical, noxious chemical-H+, noxious heat, and itching) processing corneal sensory information. Both decreased corneal chemical thresholds at high flow rates and decreased mechanical thresholds with an added chemical stimulation demonstrate that corneal psychophysical channels are not independent.
Yunwei Feng; Trefford L Simpson
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Investigative ophthalmology & visual science     Volume:  45     ISSN:  0146-0404     ISO Abbreviation:  Invest. Ophthalmol. Vis. Sci.     Publication Date:  2004 Sep 
Date Detail:
Created Date:  2004-08-24     Completed Date:  2004-10-07     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  7703701     Medline TA:  Invest Ophthalmol Vis Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3005-10     Citation Subset:  IM    
Copyright Information:
Copyright Association for Research in Vision and Ophthalmology
Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, Canada.
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MeSH Terms
Analysis of Variance
Carbon Dioxide / pharmacology
Cold Temperature
Cornea / drug effects,  physiology*
Pain / etiology
Physical Stimulation
Sensory Thresholds
Stimulation, Chemical
Reg. No./Substance:
124-38-9/Carbon Dioxide

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