Introduction
The human
eye is the organ which gives us the sense of sight, allowing us to learn
more about the surrounding world than any of the other five senses. We
use our eyes in almost everything we do, whether reading, working, watching
TV, writing a letter, driving a car, and countless other activities. Sight
is the most precious of the five senses, and many people fear blindness
more than any other disability. The eye allows us to see and interpret
the shapes, colors, and dimensions of objects in the world by processing
the light they reflect or give off. The eye is able to see in dim light
or bright light, but it cannot see objects when light is absent. The eye
changes light rays into electrical signals then sends them to the brain,
which interprets these electrical signals as visual images. The eyeball
is set in a protective cone-shaped cavity in the skull called the orbit
or socket and measures approximately one inch in diameter. The orbit is
surrounded by layers of soft, fatty tissue which protect the eye and enable
it to turn easily. Six muscles regulate the motion of the eye. Among the
more important parts of the human eye are the iris, cornea,
lens, retina,
conjunctiva, the macula, and the optic nerve.