While your cat may not have 20/20 vision, she's capable of seeing in a wide variety of environments -- particularly when it comes to dark and bright rooms. Cats don't universally prefer one over the other, but if yours has a preference, it's likely both biological and habitual.
Cat's can't "see in the dark" the way their reputation suggests -- but they can definitely see better than you when there isn't much light. Their eyes are capable of collecting and reflecting even the smallest bit of light, allowing them to see in a darkened room, so long as it isn't pitch black. They're also adept at picking up on motion and honing in on small targets, allowing them to see both predators and prey when the lights go down.
Light and Dark
Just because your cat sees well at night doesn't mean that he can't see well during the day, too. A cat's pupil expands and contracts to allow in only as much light as the eye needs. In a bright room, her pupils turn into narrow slits, while in a dark room, her pupils look as big and round as dinner saucers. Some types of cat see better at night, while some see better during the day, and this can influence whether yours prefers a dark or bright room.
The Life Nocturnal
Because domestic breeds of cat can see so well in dark environments, they have a deserved reputation as nocturnal creatures. Ones that live in the wild spend most of their waking hours hunting around sunrise and sunset, when the environment is just light enough for them -- and not necessarily other animals -- to see. If your cat prefers the dark, it could be his natural instinct taking over.
Preferences and Conditioning
Ultimately, some cats prefer the dark and others don't. If you have an indoor cat that exhibits annoying nocturnal behavior, though, you can condition her to ease up on the nighttime activity. Make sure that she gets plenty of exercise and playtime during daylight hours, and give her attention that encourages her to be awake when you are instead of snoozing all day. Even if her instincts tell her that the dark is better, you can win her over with affection and by wearing her out with playtime before you ever dim the lights.
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