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T. Simpson, J. Heath; The Pupillary Effects of Corneal Nociceptive Stimuli Applied Using a Pneumatic Belmonte Esthesiometer. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4868. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To examine the pupillary effects of nociceptive stimulation of human cornea.
A computerized Belmonte pneumatic esthesiometer was used to estimate mechanical (flow rate) and chemical (%CO2) detection thresholds using the ascending method of limits. Threshold or a suprathreshold stimuli (50% higher, order randomised and mechanical and chemical stimulus order randomised) were delivered to the central cornea while the pupils were imaged using digital video cameras directly or consensually for 10 seconds following corneal stimulation. Pupil diameters were measured subsequently using ImageJ image processing software.
Regardless of stimulus type or intensity, the pupil response after painful corneal stimulation was an initial mydriasis peaking at approximately 1.25 sec followed by a slower, more protracted miosis lasting the rest of the 10 second epoch. Average (direct or consensual) dilation ranged from 2.5 to 5.9% and constriction from 0 to 5.2%, with large inter-individual differences. The functions were well fit using a 2 compartment model using nonlinear regression.
The average direct and consensual pupillary response to painful stimuli are similar across mechanical and chemical stimulus modalities and at threshold and suprathreshold intensities and suggests a highly nonlinear pupil response to corneal nociceptive stimulation.
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