The cornea is the clear of the eye that bends the incoming light rays. The cornea can lose its clarity if it becomes inflamed or injured. Hairs and twigs can injure the cornea, especially in pop-eyed dogs. The sclera is the fibrous coat the gives the eyeball its ping-pong ball shape and dull white color. The sclera frequently takes on a yellow color.

The iris controls the amount of light entering the back of the eye and gives your dog’s eye its color. The black hole in the center of the iris is the pupil. It dilates(large) , to let more light enter in dim light, and constricts (smaler) in bright light. Cataracts are white opacities that block the lights passage through the eye, and can be seen by shining a bright light into the pupil of the eye. A normal aging process called senile cataracts, or nuclear sclerosis, is caused by a rearrangement of the fibers and a loss of water in the older lens.