The minimum stimulus energy required to produce a cooling sensation in the human cornea

Murphy, Paul James, Patel, S., Morgan, P. B. and Marshall, J. 2001. The minimum stimulus energy required to produce a cooling sensation in the human cornea. Ophthalmic and Physiological Optics 21 (5) , pp. 407-410. 10.1046/j.1475-1313.2001.00608.x

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Abstract

Purpose: To estimate the minimum stimulus energy required to stimulate the corneal nerves, using a thermally cooling stimulus. Methods: The localised temperature change produced in the pre-corneal tear film by the air-pulse stimulus of the Non-Contact Corneal Aesthesiometer (NCCA) was analysed using a thermal imaging camera. Assuming that the cornea behaves as a near perfect black-body, the threshold for energy loss was calculated by combining Stefan–Boltzmann's law and Kirchoff's law for imperfections in black-body radiation, taking into account the likely thermal conductivity of the human cornea. Results: The average normal subject has a threshold for detecting a cooling effect when the local corneal tear film surface temperature drops from a mean of 33.2–32.9°C (i.e. 0.3°C), over a 1 mm diameter circular area (0.785 mm 2 ), and a stimulus time duration of 0.9s. This gives rise to a sensation threshold for perceiving a loss of heat energy of 7.0ergs, or 7.0×10 −7 joules. Conclusion: The cornea possesses stimulus specific receptors, which have an exquisite sensitivity to a rapid, thermally cooling stimulus.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Optometry and Vision Sciences
Subjects:	R Medicine > RE Ophthalmology
Publisher:	Wiley-Blackwell
ISSN:	0275-5408
Last Modified:	04 Jun 2017 04:15
URI:	https://orca.cardiff.ac.uk/id/eprint/35566

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