Corneal pain evoked by thermal stimulation

Abstract

The thermal sensitivity of the eyelid and cornea was compared using an automated apparatus to produce stimulus pulses of known magnitude and duration over the range 33--45 degrees C. Subjects reported only temperature sensation when the skin of the upper eyelid was tested; however, corneal stimulation in the same subjects was always perceived as nociceptive. The possibility that other ocular tissues may be involved in the pain responses was shown to be unlikely by direct experimentation or by calculation of heat flow in those tissues. Cornea and eyelid thresholds were compared in relationship to the structural and physical properties of these tissues. It was found that the nerve endings of the corneal epithelium are less sensitive to temperature change when compared to the thermal receptors of the eyelid. It is concluded that the cornea is useful for the experimental study of pain.

Molecular Identities of Two Tetrodotoxin-Resistant Sodium Channels in Corneal Axons

“…However, it is thought that all these neurons are nociceptive (Beuerman and Tanelian, 1979;Chen et al, 1995). These observations and the results presented here indicate that Na v 1 .…”

Anatomical properties of brainstem trigeminal neurons that respond to electrical stimulation of dural blood vessels

“…Consistent with these previous results, most of the dura-responsive neurons in the present study received an additional afferent input from the cornea. The cornea is exceptional among tissues of the body surface in that its sensory innervation consists entirely of free nerve endings (Zander and Weddell, 1951;Whitear, 1960;Matsuda, 1967;Rozsa and Beuerman, 1982) and appears to exhibit the selectively nociceptive sensory qualities characteristic of visceral structures (Kenshalo, 1960; Beuerman and Tanelian, 1979). Thus most of the neurons in the present sample receive what appears to be a dual nociceptive afferent input from both a superfical and a deep, intracranial site.…”

CO2 Stimulation of the Cornea: A Comparison Between Human Sensation and Nerve Activity in Polymodal Nociceptive Afferents of the Cat

“…Stimulation of the human cornea with C02 elicited sensations of imtation that appear to be quite similar to those described with the application of heat (Kenshalo, 1960;Beuerman and Tanelian, 1979). In the cat's cornea, short-lasting pH reductions induced by COz or acetic acid appear to activate selectively the same group of A-delta and C-polymodal nociceptors that respond to heating of the corneal surface over 39°C (Belmonte and Giraldez, 1981;Belmonte et at., 199 1 ;Gallar et al, 1993).…”

“…Mechanical stimulation of the human cornea usually causes a sharp sensation of pain; however, reports of 'touch' sensations aroused by low-intensity stimulation of the cornea can be found in the literature (Lele and Weddell, 1956). In contrast, psychophysical experiments by Kenshalo (I 960) and Beuerman and Tanelian (1979) established that thermal stimuli elicited only sensations of irritation or pain. To our knowledge, no systematic studies of corneal sensations evoked by chemical stimulation have been performed by previous workers.…”