June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Pupillary Response to Corneal Mechanical Stimulation.
Author Affiliations & Notes
  • Emmanuel B Alabi
    SCHOOL OF OPTOMETRY AND VISION SCIENCE, UNIVERSITY OF WATERLOO, Waterloo, ON, Canada
  • Varadharajan Jayakumar
    SCHOOL OF OPTOMETRY AND VISION SCIENCE, UNIVERSITY OF WATERLOO, Waterloo, ON, Canada
  • Yunwei Feng
    SCHOOL OF OPTOMETRY AND VISION SCIENCE, UNIVERSITY OF WATERLOO, Waterloo, ON, Canada
  • Trefford L Simpson
    SCHOOL OF OPTOMETRY AND VISION SCIENCE, UNIVERSITY OF WATERLOO, Waterloo, ON, Canada
  • Footnotes
    Commercial Relationships Emmanuel Alabi, None; Varadharajan Jayakumar, None; Yunwei Feng, None; Trefford Simpson, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 582. doi:https://doi.org/
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    • Get Citation

      Emmanuel B Alabi, Varadharajan Jayakumar, Yunwei Feng, Trefford L Simpson; Pupillary Response to Corneal Mechanical Stimulation.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):582. doi: https://doi.org/.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose
 

Ocular somatosensory-autonomic reflexes play critical roles in maintaining homeostasis of the eye. The purpose of this study was to examine the pupil reflex before and after delivery of nociceptive corneal mechanical stimuli.

 
Methods
 

Using a computerized Belmonte pneumatic esthesiometer, mechanical stimuli from levels of detection threshold to twice (2x) the threshold in 0.5x steps were delivered in random order to the central cornea of 15 healthy subjects, aged 20 - 55 years. Threshold was estimated using an ascending method of limits. Contralateral pupil imaging was performed using a modified Logitech c920 digital camera (Logitech c920; Logitech International S.A., Newark, CA) for 5 seconds before and after the stimulus. Consensual pupil sizes were then measured (average of horizontal and vertical measures) using ImageJ software (NIH, Bethesda, MD). Statistical analyses were performed using Statistica 8.0 (StatSoft Inc., Tulsa, OK) and P ≤ 0.05 was considered statistically significant. Repeated-measures ANOVA and post hoc Tukey HSD tests were used to examine the effect of intensity on pupil size.

 
Results
 

The figures below show 8-bit processed images of the contralateral pupil before and after delivery of the painful corneal stimulus. The average pupil sizes were 5.82 ± 0.66mm (before stimulus delivery), 6.41 ± 0.63mm (at threshold), 6.62 ± 0.65mm (1.5x threshold) and 6.97mm ± 0.79 (2x threshold). Pupil sizes increased with increasing stimulus intensity (P < 0.05) and the maximum mechanical stimulus intensity induced the largest pupil sizes (all P < 0.05).

 
Conclusions
 

Noxious, mechanical, central, corneal stimuli evoke dose dependent sympathetic autonomic consensual pupillary dilation. This study serves as a basis for the characterization of the local stimulus-response neural circuitry relating nociceptive stimuli to autonomic responses.  

 
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