The eyes are the sensors that detect the reflected light from an object, pre-process it into a neuron signal and transmit it to the brain. The brain, after referring to its memory data bank, then identifies the object.
The eye is an almost spherical organ, about an inch in diameter, fitted with fatty tissues inside the eye socket of the skull. The sclera is the tough protective outer layer of the eye, which we see as the white of the eyes. The cornea is made of transparent, strong and smooth material that covers the colored portion of the eye. Its semi-spherical shape directs light into the pupil.
The iris, the colored portion of the eye, is made of flexible muscles, and the aperture in the center is known as the pupil. The iris muscles contract or expand to different light conditions and determine the size of the pupil. Heredity decides the color of the melanin pigment in the iris. Behind the iris is the lens. The lens focuses the light coming in through the pupil onto the retina by altering its own shape.
The retina detects the light, does the initial processing and transmits it to the brain. The eyelids, along with the lacrimal gland (tear gland), protect the eyes from injury, dust, germs and other toxic substances by automatic reflex action. We have two eyes located at a fixed distance apart, so they send two slightly varying signals according to the angle. The brain processes these and arrives at a three-dimensional image.
In an inherited condition like myopia, or near-sightedness, the distance between the lens and the retina is more than normal, so the eyes cannot see the distant objects. In the old-age problem of hyperopia, or farsightedness, the eyeball structure alters, the distance between the lens and the retina is reduced and the eyes cannot see close objects. Glasses or contact lenses can correct both these conditions. A cataract is a condition where the lens gets clouded and the vision deteriorates. Surgically replacing the lens with a synthetic lens successfully corrects the problem. Other eye diseases include conjunctivitis, astigmatism, glaucoma, sty, tumors, ectropion and entropion.
Simple precautions, such as wearing goggles in dusty areas like workshops and laboratories, and wearing sunglasses when there is harsh sunlight, go a long way in keeping these vital organs functioning smoothly for life.