Ahhh! The better to see you with, my dear! That retina glow helps them to see at night much better than us humans can.
----------------Interesting internet find...
A number of studies have been done to investigate the color vision of dogs, and the results have been conflicting. However, more recent, better controlled studies indicate that dogs do possess and use color vision, but not to the same degree that humans do. The photoreceptor used for color vision is the cone, and there are cones present in the canine retina. However, they are present in low numbers, comprising less than 10% of the total photoreceptor population in the central area of the retina, as opposed to the human retina which consists of nearly 100% cones in the fovea. Two distinct type of cones appear to be present in the canine retina. One type is maximally sensitive to light in the wavelength that appears violet to people, and the other type is maximally sensitive to light in the wavelength that appears yellow-green to people. Thus, it appears that the visual spectrum of color in dogs is divided into two hues; one in the violet and blue-violet range, probably appearing as blue, and the other in the greenish-yellow, yellow, and red range, which is probably seen as yellow. Light that appears blue-green to people probably appears as white or shades of gray to dogs. Dogs are unable to differentiate colors that appear as green, yellow-green, orange or red to people, and are unable to differentiate greenish-blue from gray. This is similar to people who are red-green color blind. However, one study indicates that dogs are better able to differentiate between subtle shades of gray than people, which would be advantageous in increasing visual discrimination in low light conditions, where insufficient light is available to stimulate cones.
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