Seeing the world through the eye of a mouse: Opportunities for refinement in laboratory animal lighting

Abstract

Light is a fundamental aspect of the environment, enabling animals to perceive and respond to visual stimuli as well as regulating circadian rhythms in physiology and behaviour. We have a good understanding of the rod and cone photoreceptors mediating vision, and work over the last 25 years has identified an additional retinal photoreceptor that regulates circadian rhythms and many other non-visual processes. This consists of a subset of intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing the blue light sensitive protein melanopsin. To address these differences in visual and circadian responses to light, in humans, standards have been introduced to provide lighting units based upon the different photoreceptors involved. By contrast, lighting in laboratory animal facilities is still based on human vision and not the experience of the animals. Recent guidelines have, for the first time, provided the tools to measure light based upon the differing visual sensitivity of laboratory species such as mice ( Mus musculus ). Here, we provide an overview of why this is important, for both science and animal welfare, and how researchers and animal care staff can apply these new methods in their work. For the first time, this provides refinement opportunities to optimise lighting based on the animal’s experience of their light environment.