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P. Situ, T. L. Simpson; Evoked Sensation by Mechanical and Chemical Stimulation in Central and Peripheral Cornea. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5387.
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In a previous study, we found that pneumatic mechanical and chemical thresholds were similar between central and peripheral cornea. This study was to determine whether central and peripheral cornea respond differently to mechanical and chemical stimulation at suprathreshold levels.
Nine healthy human subjects participated in the study. Mechanical and chemical stimuli were set at and above thresholds and delivered to central and temporal peripheral cornea (about 2mm from limbus) using the Belmonte pneumatic esthesiometer. The magnitude of the evoked sensation was estimated with free range scales i.e. subject could assign any number to the presented stimuli. The relationship between the physical intensity of various stimuli and the normalised sensory magnitudes was estimated and was compared between the two locations in the cornea.
The sensations evoked by mechanical and chemical stimuli in central and peripheral cornea were nociceptive in nature. The size of the power exponents between central and peripheral cornea were similar (paired t-test, p>0.05) while the exponents for mechanical and chemical stimulation were different (paired t-test, p<0.05).
It appeared that suprathreshold functioning of the peripheral cornea did not differ from that of the central cornea, suggesting that the scaling of the transduction of stimulus energy into neural impulses was similar between corneal locations but there may be different suprathreshold transducer scaling for mechanical and chemical stimuli.
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