title: Quantitative assessment of the canine pupillary light reflex.
abstract: OBJECTIVE
  To develop instrumentation and methods for thorough quantitative assessment of the pupillary light reflex (PLR) in dogs under varying stimulus conditions.
  
  
  METHODS
  The PLR was recorded in normal Dachshunds using a custom system allowing full user control over stimulus intensity, color, and duration. Chemical restraint protocols were compared to determine which protocol provided for optimal baseline stability of pupil size and appropriate eye positioning. A series of white light stimuli of increasing intensity was used to elicit pupil constriction. Pupil images were concurrently recorded using continuous infrared illumination and an infrared-sensitive camera. The PLR was also recorded in response to blue and red stimuli.
  
  
  RESULTS
  With injectable chemical restraint alone, spontaneous fluctuations in pupil size occurred independent of light stimulation, and spontaneous eye movements made it difficult to fully visualize the pupil. Combined injectable chemical and inhalation restraint provided a steady baseline pupil size throughout PLR assessment and allowed for stable positioning of the eye using a conjunctival stay suture. Robust PLRs were elicited with all light colors. PLR constriction amplitude increased with increasing flash intensity and ranged from 5% to 70%.
  
  
  CONCLUSIONS
  A recording system and protocol have been developed to reliably quantify the canine PLR. The techniques and instrumentation will be useful for objective quantitative assessment of the PLR in dogs and other species in research applications and may be useful in clinical veterinary ophthalmology and neurology if PLR abnormalities detected with these procedures can be associated with specific diseases.
authors.affiliation: Department of Biological Engineering, College of Engineering, University of Missouri, Columbia, Missouri 65212, USA.
authors.forename: Rebecca E H
authors.initials: RE
authors.lastname: Whiting
authors.forename: Gang
authors.initials: G
authors.lastname: Yao
authors.forename: Kristina
authors.initials: K
authors.lastname: Narfström
authors.forename: Jacqueline W
authors.initials: JW
authors.lastname: Pearce
authors.forename: Joan R
authors.initials: JR
authors.lastname: Coates
authors.forename: John R
authors.initials: JR
authors.lastname: Dodam
authors.forename: Leilani J
authors.initials: LJ
authors.lastname: Castaner
authors.forename: Martin L
authors.initials: ML
authors.lastname: Katz
mesh_terms: D000818:Animals; D004285:Dogs; D004596:Electroretinography; D005133:Eye Movements / Q000502:physiology; D010775:Photic Stimulation; D011680:Pupil / Q000502:physiology*; D012025:Reflex, Pupillary / Q000502:physiology*; D017299:Rod Opsins / Q000378:metabolism; D000099210:Melanopsin
chemical_list: D017299:Rod Opsins; D000099210:Melanopsin
keywords: animal model; dog; electroretinogram; melanopsin; pupillary light reflex