Peer-reviewed veterinary case report
How pupil light reflex tests show retinal health in dogs
By Grozdanic, Sinisa D et al.·Published in Investigative ophthalmology & visual science·2007·Department of Veterinary Clinical Sciences, United States·View original on PubMed →
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Original publication title: Evaluation of retinal status using chromatic pupil light reflex activity in healthy and diseased canine eyes.
- Species:
- dog
Plain-English summary
A group of healthy dogs and dogs with sudden acquired retinal degeneration syndrome (SARDS) were tested to see how their pupils reacted to different colors and intensities of light. Healthy dogs showed normal pupil responses even in low light, while dogs with SARDS, who were completely blind, only responded to bright blue light and not to red light at all. This suggests that in SARDS, the usual vision pathways are damaged, but some light sensitivity remains through a different mechanism. Understanding these responses can help veterinarians assess vision problems in dogs.
People also search for: dog eye problems · SARDS in dogs · canine pupil response to light · dog blindness symptoms · treatment for dog vision loss
Abstract
PURPOSE: To differentiate rod-cone-mediated pupil light reflexes (PLRs) from intrinsic melanopsin-mediated pupil light reflexes by comparing pupil responses with red and blue light stimuli of differing intensities in normal dog eyes and in those with sudden acquired retinal degeneration syndrome (SARDS) exhibiting a nonrecordable electroretinogram. METHODS: The PLR was evaluated in 14 healthy dogs using a computerized pupillometry system and in five dogs with SARDS. Contraction amplitude, velocity, and implicit time of the PLR were studied as a function of peak wavelength (480 nm vs. 630 nm) and light intensity (-0.29 to 5.3 log units) to determine characteristics of the rod-cone versus predominantly melanopsin-mediated PLR activity. RESULTS: The PLR in healthy, mildly sedated dogs could be elicited at low light intensities (-0.29 log units; 0.51 cd/m(2)). Canine SARDS patients displayed a complete absence of vision, electroretinographic amplitude, and PLR at low light intensity. However, in SARDS dogs, a pupil light reflex could be elicited with wavelengths corresponding to the melanopsin spectral sensitivity (blue light - peak at 480 nm) and at relatively high intensity (4.3 log units or higher), whereas red light (630 nm peak wavelength) was ineffective in eliciting any detectable PLR response even at light intensities of 6 log units (1,000,000 cd/m(2)). CONCLUSIONS: The PLR in healthy canine eyes can be elicited at very low light intensities using red and blue wavelengths of light, but in dogs with blindness caused by SARDS, the pupil reacts only to high-intensity blue wavelength light, implying loss of the rod-cone-mediated PLR and most likely the presence of intrinsic, melanopsin-mediated, retinal ganglion cell-mediated PLR.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/17962471/