The human camera: eye

How the Human Eye Works

The human eye is like a camera. Light comes in through the cornea, a clear cover that is like the glass of a camera's aperture. The pupil, an opening that opens and closes a little like a camera shutter, controls the amount of light coming in.

The light focuses on the retina, a series of light sensitive cells lining the back of the eye. The retina acts like camera film, reacting to the incoming light and sending a record of it via the optic nerve to the brain. Other parts of the human eye play a supporting role in the main activity of sight:

• Some carry fluids (such as tears and blood) to lubricate or nourish the eye.
• Others are muscles that allow the eye to move.
• Some parts protect the eye from injury (such as the lids and the epithelium of the cornea).
• And some are messengers, sending sensory information to the brain (such as the pain-sensing nerves in the cornea and the optic nerve behind the retina.

As a conscious sense organ the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 16 million colors.

Structure:

• Human eye is divided in two main part front part is called cornea and back part is called sclera attached with cornea. Inner side is aqueous humor. Lens and muscles are present.
• The dimensions differ among adults by only one or two millimeters. The vertical measure, generally less than the horizontal distance, is about 24 mm among adults, at birth about 16–17 mm. (about 0.65 inch) The eyeball grows rapidly, increasing to 22.5–23 mm (approx. 0.89 in) by the age of three years. From then to age 13, the eye attains its full size. The volume is 6.5 ml (0.4 cu. in.) and the weight is 7.5 g. (0.25 oz.)
• Human eye vision is determined by brain area near occipital lobe.
• Eye is protected by anti bacterial material fluished over the cornea,eye brows, and eye lids.

For further information contact: www.eehealthbook.com

Or email us: eehealthbook@hotmail.com