title: Assessment of Rod, Cone, and Intrinsically Photosensitive Retinal Ganglion Cell Contributions to the Canine Chromatic Pupillary Response.
abstract: The purpose of this study was to evaluate a chromatic pupillometry protocol for specific functional assessment of rods, cones, and intrinsically photosensitive retinal ganglion cells (ipRGCs) in dogs.
  
  
  
  Chromatic pupillometry was tested and compared in 37 dogs in different stages of primary loss of rod, cone, and combined rod/cone and optic nerve function, and in 5 wild-type (WT) dogs. Eyes were stimulated with 1-s flashes of dim (1 cd/m2) and bright (400 cd/m2) blue light (for scotopic conditions) or bright red (400 cd/m2) light with 25-cd/m2 blue background (for photopic conditions). Canine retinal melanopsin/Opn4 was cloned, and its expression was evaluated using real-time quantitative reverse transcription-PCR and immunohistochemistry.
  
  
  
  Mean ± SD percentage of pupil constriction amplitudes induced by scotopic dim blue (scDB), scotopic bright blue (scBB), and photopic bright red (phBR) lights in WT dogs were 21.3% ± 10.6%, 50.0% ± 17.5%, and 19.4% ± 7.4%, respectively. Melanopsin-mediated responses to scBB persisted for several minutes (7.7 ± 4.6 min) after stimulus offset. In dogs with inherited retinal degeneration, loss of rod function resulted in absent scDB responses, followed by decreased phBR responses with disease progression and loss of cone function. Primary loss of cone function abolished phBR responses but preserved those responses to blue light (scDB and scBB). Although melanopsin/Opn4 expression was diminished with retinal degeneration, melanopsin-expressing ipRGCs were identified for the first time in both WT and degenerated canine retinas.
  
  
  
  Pupil responses elicited by light stimuli of different colors and intensities allowed differential functional assessment of canine rods, cones, and ipRGCs. Chromatic pupillometry offers an effective tool for diagnosing retinal and optic nerve diseases.
authors.affiliation: College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States 2School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States.
authors.forename: Connie Y
authors.initials: CY
authors.lastname: Yeh
authors.affiliation: College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States.
authors.forename: Kristin L
authors.initials: KL
authors.lastname: Koehl
authors.affiliation: College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States.
authors.forename: Christine D
authors.initials: CD
authors.lastname: Harman
authors.affiliation: School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States.
authors.forename: Simone
authors.initials: S
authors.lastname: Iwabe
authors.affiliation: School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States.
authors.forename: José M
authors.initials: JM
authors.lastname: Guzman
authors.affiliation: College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States.
authors.forename: Simon M
authors.initials: SM
authors.lastname: Petersen-Jones
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, United States 4Veterans Affairs Health Care System, Iowa City, Iowa, United States.
authors.forename: Randy H
authors.initials: RH
authors.lastname: Kardon
authors.affiliation: College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States 2School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States.
authors.forename: András M
authors.initials: AM
authors.lastname: Komáromy
mesh_terms: D000818:Animals; D004285:Dogs; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D033401:Microscopy, Acoustic; D023421:Models, Animal; D010775:Photic Stimulation; D012313:RNA / Q000235:genetics; D012025:Reflex, Pupillary / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000502:physiology*; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017299:Rod Opsins / Q000096:biosynthesis / Q000235:genetics; D000099210:Melanopsin
chemical_list: D012313:RNA; D017299:Rod Opsins; D000099210:Melanopsin