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Corneal pain evoked by thermal stimulation
1Division of Ophthalmology SO18, Stanford University Medical Center, Stanford, Calif. 94305 U.S.A.
Pain
|August 1, 1979
Summary
The cornea, unlike the eyelid, triggers pain when exposed to heat. Corneal nerve endings are less sensitive to temperature, making the cornea valuable for pain research.
Area of Science:
- Ophthalmology
- Neuroscience
- Sensory Physiology
Background:
- The thermal sensitivity of ocular tissues is not fully understood.
- Distinguishing between temperature sensation and nociception is crucial for ocular research.
Purpose of the Study:
- To compare the thermal sensitivity thresholds of the eyelid and cornea.
- To investigate the potential involvement of other ocular tissues in thermal pain perception.
- To assess the suitability of the cornea for experimental pain studies.
Main Methods:
- Utilized an automated apparatus to deliver controlled thermal stimulus pulses (33–45°C) to the eyelid and cornea.
- Compared subject responses (temperature sensation vs. nociception) between the two tissues.
- Evaluated heat flow and performed direct experimentation to rule out other ocular tissue involvement.
Main Results:
- Eyelid stimulation elicited only temperature sensation.
- Corneal stimulation consistently resulted in nociceptive (pain) perception.
- Corneal epithelium nerve endings demonstrated lower thermal sensitivity compared to eyelid thermal receptors.
- Other ocular tissues were deemed unlikely contributors to observed pain responses.
Conclusions:
- The cornea's distinct response to thermal stimuli suggests it is a valuable model for experimental pain research.
- Differences in thermal sensitivity between the cornea and eyelid are linked to their structural and physical properties.