Eye
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  Eye



Eye

   The organ of sight. The eye has a number of components. These components include but are not limited to the cornea, iris, pupil, lens, retina, macula, optic nerve, choroid and vitreous.

RELATED TERMS
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Organ
A structural unit of an animal or plant that serves a specific function.

Cornea
The front part of the eye that acts as a window for the entrance of light rays. It is attached to the other outer coat of the eye, the sclera; the white part of the eye. The cornea provides a significant amount of focusing power for the eye (the rest is provided by the lens). Because it has many nerve fibers, an injury or foreign body causes significant pain and discomfort.

Iris


Pupil
A circular opening in the center of the iris. The size of the pupil changes according to the amount of light present. It is small in sunlight and large in a dark room.

Lens
The lens of the eye is like an adjustable lens of a camera and focuses light rays on to the retina for sharp images. A condition called presbyopia occurs when the lens is no longer able to adjust for objects at different distances.

Retina
A membrane lining the inside of the back of the eye that contains light-sensitive nerve cells that convert focused light into nerve impulses, making vision possible.

Macula
A specialized part of the retina containing mostly cones. The macula is used for all detailed visual tasks. The center of the macula is called the fovea. If a disease process harms or destroys the macula, vision is usually reduced to 20/200 (legal blindness).

Nerve
Tissue that conveys sensation, temperature, position information to the brain.

Choroid
This is the vascular coat between the sclera and the retina, which furnishes blood and nutrition to the outer layer of the retina.

Vitreous
The transparent, solid, gelatinous material which fills the interior of the eye behind the lens. It allows the eye to maintain its shape.



SIMILAR TERMS
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Exudate
A fluid rich in protein and cellular elements that oozes out of blood vessels due to inflammation and is deposited in nearby tissues. The altered permeability of blood vessels permits the passage of large molecules and solid matter through their walls.

Exudative angina
This has nothing whatsoever to do with the usual type of angina (angina pectoris) which is chest pain of cardiac origin. Angina trachealis is more commonly known as croup. This is an infection of the larynx, trachea, and the bronchial tubes, that occurs mainly in children. It is usually caused by viruses, less often by bacteria. Symptoms include a cough that sounds like a barking seal and a harsh crowing sound during inhaling.

EYCL1
A gene for green/blue eye color located on chromosome 19.

EYCL2
A gene for brown eye color.

EYCL3
A gene for brown/blue eye color located on chromosome 15.

Eye

Eye bank
A place to store corneas (the clear "front window" of the eye) for use in future keratoplasty (surgery to replace the cornea).

Eye bleed
Medically called a subconjunctival hemorrhage. A very common cause of a painless bloody eye usually first noticed by somebody else or by the person with it when they look in the mirror. The bleeding results from a break in a small blood vessel in the sclera, the white of the eye. This releases a tiny amount (less than a drop) of blood which is trapped underneath the conjunctiva, much like the blood in a bruise is trapped in the skin. It is called a subconjunctival hemorrhage since it occurs beneath the conjunctiva, the transparent membrane covering the sclera.

Eye cataract
A clouding of the lens of the eye. The normally clear aspirin-sized lens of the eye starts to become cloudy. The result is much like smearing grease over the lens of a camera. It impairs normal vision.

Eye color
The color of the iris. The genetics of eye color are complicated. Eye color is polygenic. It is determined by multiple genes. The eye color genes include EYCL1 (a green/blue eye color gene located on chromosome 19), EYCL2 (a brown eye color gene) and EYCL3 (a brown/blue eye color gene located on chromosome 15). There are clearly other genes that influence eye color. The once-held view that blue eye color is a simple recessive trait has been shown to be wrong. The genetics of eye color are so complex that almost any parent-child combination of eye colors can occur.

Eye pressure test
A standard eye test that determines the fluid pressure inside the eye. The test is called tonometry.Increased pressure within the eye is a possible sign of glaucoma, a common and potentially very serious eye problem if it is not detected and treated promptly. It is recommended that adults over age 40 have tonometry for glaucoma every 3 to 5 years by having their eye pressures measured.

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