Abstract
Purpose :
Different species block varying amounts of wavelengths in the ultraviolet (UV) spectrum to protect the retina. However, evolution of UV vision in some mammalian species is thought to aid in environmental navigation, communication, and foraging behavior. Specifically, dogs and cats are suspected to have UV vision although the percent transmission (%T) of UV light reaching the retina is not clearly defined. The aim of this study is to assess the transmission of the UV spectrum (200-400 nm) through enucleated globes of different species (dogs, cats, rabbits, pigs, and humans) using spectrophotometry.
Methods :
Globes (n=6-10 per species) from animal models were analyzed within 24 hours of death. Human globes (n=2) were acquired from an eye bank. For spectrophotometry, a 5-10 mm circular area of sclera and choroid from the posterior aspect of the globe was removed under a surgical microscope. The retina remained intact to mimic the path of light through the living eye. The %T of wavelengths from 200-800 nm were measured through the ocular media (cornea, aqueous humor, lens, and vitreous humor) and retina of dogs, cats, pigs, rabbits, and humans. The %T within the UV range (200-400 nm) and UV-Visible range (200-800 nm) were compared between species. Data was analyzed using area under the curve and ANOVA with significance set at p<0.05.
Results :
Compared to other species, there was a significantly larger amount of UV %T in globes of dogs and cats (p<0.0001). Cats transmitted the highest percentage of UV light with over 59% transmission at 400 nm whereas dogs transmitted 27% of light at 400 nm. At 350 nm, cats transmitted 30% of light and dogs transmitted 9%. There was also a significantly larger amount of UV %T in globes of rabbits compared to pigs (p=0.0021) and humans (p=0.0150). Rabbits transmitted 27% of light at 400nm and less than 1% at 350 nm. Humans and pigs did not differ significantly in the amount of UV %T (p=0.9985) and transmitted less than 1% of light below 400nm.
Conclusions :
Dogs and cats have significantly higher transmission of wavelengths below 400 nm through their ocular media and retina compared to rabbits, pigs, and humans. This suggests that these crepuscular species can take advantage of UV light both in nature and under artificial lighting conditions. Results from this study will support further vision research in cats and dogs. These results may be used to train companion, working, and service animals.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.