If you've ever seen a newborn kitten you probably know that it takes some time for her to open her eyes. And even after her eyes are open, her eyesight is still pretty poor. It will take kitty about two months to fully develop her eyesight.
Newborn kittens have sealed eyelids, which begin to open around eight days. It's not at all unusual for littermates to open their eyes at different rates -- some babies may open their eyes in as little as two days while others may take as long as two weeks. However, once open, their eyes will be blue and will gradually mature. Kittens will try to avoid light for two or three days after their eyes open because their pupils aren't able to constrict.
The First Three Weeks
The first three weeks of kitty's life she's especially dependent on her mother. Not only are her eyes not real useful, but her hearing isn't fully developed. As well, she's just beginning to get her legs moving, so she's not as mobile as she soon will be. Because her eyesight is still rather poor, she relies on smell, touch and sensing body heat to find her mother and littermates.
Three to Six Weeks
When Kitty's about three weeks old she's got more blood flowing to her eyes, so her vision has begun to improve. In another week she'll start getting some depth perception, so she won't bump into things quite so much. By the time she's six weeks old her eyesight should start improving to the point where she can find food on her own and avoid things in her path. You'll probably also notice that her eyes are beginning to change color at this point.
Kitty will have her grown-up vision around the two-month mark. Her sharpest vision will be between 2 and 3 feet in front of her, and instead of taking in a wide area, she'll focus on what's directly in front of her. This helps her when she's stalking small prey. Kitty's keen eyes are very adept at detecting motion, also helpful when she's hunting, particularly because her peripheral vision is not as good as her predator vision.
Cats may not be able to see in the dark, as many believe they do, but their pupils adapt well in low-light situations so they can take in as much light as possible. Their pupils also respond to stressful situations. If Kitty's in a situation that has her on alert, her pupils will dilate so she has a wider field of vision and can take in as much of her environment as possible.