Concept
Cat senses are adaptations that allow cats to be highly efficient predators. Cats are good at detecting movement in low light, have an acute sense of hearing and smell, and their sense of touch is enhanced by long whiskers that protrude from their heads and bodies. These senses evolved to allow cats to hunt effectively at dawn and dusk. Cats have a tapetum lucidum, which is a reflective layer behind the retina that sends light that passes through the retina back into the eye. They also have a high number of rods in their retina that are sensitive to dim light. While these improve the ability to see in darkness and enable cats to see using roughly one-sixth the amount of light that humans need, they appear to reduce net visual acuity, thus detracting when light is abundant. A cat's visual acuity is anywhere from 20/100 to 20/200, which means a cat has to be at 6 metres to see what an average human can see at 20 or 30 metres. Cats seem to be nearsighted, which means they cannot see far objects as well. The ability to see close objects would be well-suited for hunting and capturing prey. In very bright light, the slit-like pupil closes very narrowly over the eye, reducing the amount of light on the sensitive retina, and improving depth of field. Big cats have pupils that contract to a round point. Variation in color of cats' eyes in flash photographs is largely due to the reflection of the flash by the tapetum. Cats have a visual field of view of 200° compared with 180° in humans, but a binocular field (overlap in the images from each eye) narrower than that of humans. As with most predators, their eyes face forward, affording depth perception at the expense of field of view. Field of view is largely dependent upon the placement of the eyes, but may also be related to the eye's construction. Instead of the fovea, which gives humans sharp central vision, cats have a central band known as the visual streak. Common for carnivorans (and most mammals), cats are dichromats with two types of cone opsins, LWS (OPN1LW) and SWS1 (OPN1SW), somewhat similar to a human with protanopia.
