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Ariadna Diaz-Tahoces, Enrique Velasco, Miguel Delicado-Miralles, Fernando Aleixandre-Carrera, M Carmen Acosta, Juana Gallar; Corneal blink reflex amplitude and thermal sensation are proportional to corneal surface temperature changes. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4716.
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© ARVO (1962-2015); The Authors (2016-present)
Corneal blink reflex is initiated by changes in neural activity of the trigeminal ganglion (TG) neurons innervating the cornea. It also involves neurons located at the trigeminal system brainstem nuclei, interneurons of the reticular formation, and motor neurons in the facial nucleus that innervate the orbicularis oculi muscle (OO), which electrical activity constitutes the efferent arm of the reflex blink circuit. In this work, we studied the relationship between the intensity of the thermal (cold and heat) stimulation of the cornea and both, the characteristics of the induced blink reflex and the evoked sensation.
Ten volunteers (5 female/5 male) participated in the study. Saline solution drops (40µl) at different temperatures (n=200; 20 drops/subject) were instilled every 3 min onto the left eye (OS) to induced corneal surface temperature (CST) changes, between 23°C and 44°C (basal CST=34.62°C±0.77°C). Superficial electromyography of the orbicularis oculi muscle (OOemg) of both eyes and InfraRed (IR) video images of OS were recorded simultaneously. OOemg signals were amplified, filtered and stored for off-line analysis of its duration and the area under the curve (AUC). CST was measured from IR video images using dedicated software. After each drop, the subjects also scored the subjective intensity of the evoked sensation with a 0-10 numerical rate scale (NRS).
Unilateral instillation of thermal stimuli evoked OOemg signals in both eyes, being the amplitude of the AUC and the duration of the OOemg signals induced by cooling (r=0.555, p<0.0001) and heating (r=0.723, p<0.0001), proportional to the change in the CST.NRS values of subjective intensity of the sensation correlated positively with the CST changes induce by both, cold and heat stimuli (r=0.808 and r=0.815, p<0.0001 respectively). A significant correlation (p<0.0001) was also found between the OOemg parameters (AUC and duration) and the intensity NRS values.
The sensory input driven by activation of the corneal nerve endings by cold and heat stimuli evokes conscious sensations and also induces a reflex blink response, whose amplitude and duration is proportional to the corneal temperature change produced by the applied stimulus.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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