Assessment of Corneal Sensitivity

Schirmer, K. E.

doi:10.1136/bjo.47.8.488

Cited by 17 publications

(11 citation statements)

References 7 publications

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“…Recent psychophysical experiments on corneal sensibility have confirmed the view C. BELMONTE AND F. GIRALDEZ that nocifensive reflexes, irritation and pain are the only reactions to thermal stimulation of the human cornea (Kenshalo, 1960;Beuerman & Tanelian, 1979). This is also the case for mechanical stimulation except for periliminal intensities (Lele & Weddel, 1956;Schirmer, 1963). These observations suggest the corneal endings could share some functional properties with other somatic nociceptors.…”

Section: Introductionmentioning

confidence: 81%

“…Contact thresholds for the sensory response, estimated with the Cochet-Bonnet aesthesiometer or similar instruments, are about 20-30 mg (Schirmer, 1963;Millodot, 1973). A low threshold to pain, a high sensitivity to moving stimuli and the persistence of the sensation outlasting mechanical stimulation are characteristics of the corneal sensation (Lele & Weddell, 1956;Schirmer, 1963). The sensory response to heating changes from neutral to irritating at 38-42 'C and from very irritating to painful at 44 47 'C.…”

Section: Discussionmentioning

confidence: 99%

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Responses of cat corneal sensory receptors to mechanical and thermal stimulation.

Belmonte¹,

Giráldez²

1981

The Journal of Physiology

150

107

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SUMMARY1. The afferent responses evoked by mechanical and thermal stimulation of the cat cornea were recorded extracellularly from strands of long and mixed ciliary nerves under deep anaesthesia. 94 % of the units studied (n = 53) responded consistently to both stimuli.2. Conduction velocities, measured by electrical stimulation of the receptive field, corresponded to the lower range of the A-delta fibre group (average = 5-4 m/sec). Receptive fields covered approximately a quadrant of the corneal surface and showed continuous sensitivity and overlapping. Units were silent in the absence ofstimulation but an ongoing activity was commonly present after repeated mechanical and thermal stimulation.3. Mechanical responses were evoked at low thresholds and consisted of a dynamic and static response that paralleled the amplitude of the stimulus. The pattern of the discharge was irregular and fatigue was easily developed by repeated stimulation.4. Thresholds to heating were above 38 'C and the response increased monotonically with the temperature over the range from threshold to 50 'C. The heat response could be sensitized by repeated long suprathreshold stimulation while variable changes in the response were induced by briefer stimuli. Also depression was observed in some circumstances. A weak response to cooling was present in 50 % of the units tested.5. Damaging mechanical stimulation or the application of a strong acid solution evoked a vigorous response followed by an after discharge that persisted for hours.6. The relation of these receptors to other polymodal nociceptors and corneal sensation is considered.

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Section: Introductionmentioning

confidence: 81%

Section: Discussionmentioning

confidence: 99%

Responses of cat corneal sensory receptors to mechanical and thermal stimulation.

Belmonte¹,

Giráldez²

1981

The Journal of Physiology

150

107

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“…They were excited by small temperature decreases of the corneal surface in a range between 30 and 8°C, but were not responsive to noxious heat. INTRODUCTION Pain is the dominant sensation elicited by mechanical, chemical or thermal stimulation of the human cornea (Kenshalo, 1960;Schirmer, 1963 Tanelian, 1979; but see Lele & Weddell, 1956). Thus, psychophysical evidence would suggest that most if not all corneal sensory afferents are nociceptive in nature.…”

mentioning

confidence: 99%

Response of sensory units with unmyelinated fibres to mechanical, thermal and chemical stimulation of the cat's cornea.

Gallar

Pozo

Tuckett

et al. 1993

The Journal of Physiology

194

171

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SUMMARY1. In the cat anaesthetized with sodium pentobarbitone, electrical activity was recorded from single unmyelinated sensory fibres innervating the cornea.2. Based on their response to mechanical (calibrated aesthesiometer), chemical (10 mm acetic acid or 616 mm NaCl) and thermal (cooling from 35 to 5°C; heating to 51°C) stimuli, corneal unmyelinated fibres were classified as polymodal (71 %) or 'cold' nociceptors (29 %).3. Polymodal units responded to mechanical indentation of the cornea and developed fatigue after repeated stimulation. They were excited by temperatures over 37°C and exhibited sensitization to repeated heating.4. Corneal polymodal units were also activated by topical application of 10 mM acetic acid and hypertonic NaCl (616 mM). Capsaicin (0 33 mM) elicited a discharge of impulses that was followed by inactivation to mechanical, chemical and thermal stimuli.5. 'Cold' nociceptors had small receptive fields, preferentially located at the periphery of the cornea. They were excited by small temperature decreases of the corneal surface in a range between 30 and 8°C, but were not responsive to noxious heat.6. 'Cold' nociceptors encoded temperature changes between 35 and 23 'C. The discharge was proportional to the velocity of the temperature drop; sustained temperatures were not signalled by changes in static frequency values. 'Cold' nociceptive fibres responded to hypertonic NaCl (616 mM) and weakly to 10 mM acetic acid. Capsaicin (0 33 mM) first excited and then inactivated 'cold' nociceptors.7. Thermoreceptive fibres were found in the episclera. They fired in bursts and responded to small temperature decreases, but were insensitive to irritant chemicals and capsaicin.

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“…Studies which have been reported by Schirmer [2], Larson [3], Radzichovskiy [4], Gotz [5] and Draeger [6] are interesting. followed by a phase of diminished sensitivity.…”

Section: Introductionmentioning

confidence: 87%