To adapt to low light, cats like many carnivores have a special layer on the back of the retina called the tapetum lucidum . This special cell layer takes the light coming into they eye, magnifies it and reflects it to the retina, like an amplifier. Cats eyes are also relatively large compared to other carnivores, which allows the pupils to increase in size a greater distance. Also, the cornea and lens are more sharply curved, which increases the sensitivity of the retina. Rods are more responsive to lower levels of light than cones, thus cats have more rods than most mammals.
Cats can also control the amount of light coming into their eyes better than other mammals.
The little cats, who have a slit-shaped pupil, can close their pupils almost entirely, and open them to cover their entire eye. Bigger cats eyes, although they don't look it, are in fact elliptical in shape, just to a lesser degree. Cats, being carnivores, have their eyes located on the very front of their face, which allows depth perception, and accuracy, both of which are very important in hunting. However, cats eyes are located more closely together than those of other carnivores, making their binocular vision better than dogs or bears. This illustrates how much the cat can change its eye shape and size.