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Issue: 74 - Feb 16, 2015
Design for Your Patients’ Vision
By: Heather E. Lewis, AIA, NCARB
Animal Arts

Vision is very different in dogs and cats than it is in humans.  The way that companion animals experience the world around them should influence how we design spaces for their comfort and wellbeing. 

Let’s start with an understanding of WHY animals perceive their environments differently.  Dogs and cats have traded superior perception of color for superior vision in low light conditions.  Cats especially have particularly acute vision at night.  In contrast, humans don’t see well in low light, but we do see colors very well.

Dogs have dichromatic vision, and they lack perception of color within certain wavelengths of light.  Specifically, they don’t see orange and red very well.  They do see the other colors we identify, just not as brightly.  Cats have trichromatic vision, but they too don’t perceive orange and red.

The most fascinating fact about the vision of dogs and cats is that they see into the ultraviolet end of the spectrum.  We humans do not see ultraviolet light, although it is possible to mimic the way that a dog or cat sees by shining an ultraviolet light over a surface.  Because cats and dogs can see ultraviolet light, they also see items that fluoresce under UV light, namely materials containing phosphorous (such as urine).  Some manmade materials that have had whiteners and brighteners added to them also look different to cats and dogs.  These materials may include paper, some plastics, and white fabrics.

While we don’t know for sure that animals respond better to colors they can see, we believe they may.  This hunch is supported by some studies.  At the very least, it is important to understand how a dog or cat perceives the environment so we can be sensitive to things that may be visually jarring, such as white or clear plastics that glow brightly in the UV spectra that we cannot see.  In general, it may be best to avoid white or clear plastics in animal environments, particularly in caging.

As we are interested in designing environments that animals find more comforting, we’d like to suggest choosing light color schemes that are centered on the blue, green, or violet end of the spectrum.  The reason for choosing a light color scheme is to allow the animal to perceive their environment well, even when the lighting is lowered or turned off. 

How can the concepts that we have discussed be applied to lighting design?  How might you choose lighting that is more natural and pleasant for the way dogs and cats see?  Let’s begin by narrowing the choices.  In commercial construction, we architects and engineers are able to choose either fluorescent or LED lighting sources.  Of the two, LED has a far more even spectral distribution than fluorescent does.  Most of us are aware that fluorescent lighting can appear harsh and unflattering.  This has to do with strong spectral peaks, which occur in yellow, red, and green.  In other words, fluorescent lighting is more uneven for an animal than it is for us, as they cannot perceive the red output of the lamp. 

For this reason, we believe that LED lighting is better for lighting an animal space.  LED lighting is also more easily dimmable, which may be a nice feature to cut down on the stress in a ward when full lighting levels are not necessary.  But LED lighting is expensive, so if it’s not in your budget, at least purchase “full-spectrum” fluorescent bulbs, which even out the color differences somewhat and feel a bit more natural.  If possible, it is always best to incorporate natural daylighting into animal housing and medical spaces, as daylight is evenly distributed across the visual spectra, including ultraviolet.

As we collectively learn more about the way that animals see, we will continue to develop solutions that are less about people and more about animals.  We may not change the world for an animal by selecting the right light bulb, but we can make a huge difference in the lives of animals by creating environments that are tuned to their senses, and are as stress free and natural as possible.