Q: How does the eye work?
A: Like a finely engineered machine, in order for the eye to see properly, all of the eye's parts must function properly, all of the eye's parts must function in perfect synergism. The transparent surface of the eye through which light enters is called the cornea. The cornea must be absolutely clear. If the cornea should become diseased or opaque it can be replaced with a new cornea from a donor, through a procedure called a corneal transplant. Once the light enters the eye through the cornea, it passes through a small hole in the iris called a pupil. The iris works very much like the lens of a camera. It opens up the pupil (dilates) to let in more light when it is dark and closes up the pupil (constricts) to let in less light when it is very bright. Directly behind the pupil is a clear, gelatin-like lens, wrapped in a clear protective membrane called its capsule. The lens is responsible for focusing the images that you see to the back of the eye. If the lens becomes opaque, then the lens becomes known as a cataract.
Q: How does the image then get to the brain?
A: The image passes through the vitreous, a clear gel that fills the eye, and the image is then focused onto the retina at the back of the eye. The retina records the image, very much like film in a camera, and sends the image by way of the optic nerve to the brain.
Q: How does the retina function?
A: The retina is responsible for changing images into electrical impulses which are sent to the brain. The retina is nourished by tiny blood vessels located in the layers in the back of the eye. There are areas on the retina that are responsible for different types of vision. One such area located near the optic disk is the macula. The macula is responsible for straight ahead, or central vision. Located throughout the retina are light sensing cells called rods and cones. Cones are responsible for color and central vision. Rods are responsible for night and side vision.
Q: How does the movement of the eye happen?
A: Movement of the eyes...up, down, sideways, is controlled by a set of six muscles attached to the eyeball. To see correctly, both eyes must move at the same time, the same distance and the same direction. To do this the brain tells a set of muscles to pull and the opposite set of muscles to relax...thus the eye can move in all directions. If the eye muscles are not coordinated in their movement, double vision may occur. This uncoordinated movement is called strabismus. If the wandering eye is not corrected, loss of vision may occur, leading to an extreme case of amblyopia.