User:Itesha Gordon

= Structure and Function of the Eye =

'''An eye is an organ that detects light and send signals along the optic nerve to the brain. in humans the eye is a valuable sense organ that gives us the ability to see. it allows for light perception and vision, including the ability to differentiate between colors and depth.'''

Functions of the part of the Eye
Conjunctiva: thin membrane which stop grit entering skull orbit and protect the eye.

Cornea: transparent window; refracts light which passes through it.

Iris: controls pupil size.

Aqueous humor: refracts light, helps maintain shape.

Pupil: aperture allowing light through.

Lens: become more or less convex to focus light on retina.

Suspensory Ligaments: Supports lens

Ciliary muscle in ciliary body: contracts and relaxes to alter the shape of the lens.

Choroid: well supplied with capillaries for nutrition and Oxygen.

Sclera: tough fibrous layer, keeps spherical shape.

Yellow Spot: Centre of field of vision, provides detailed vision, cones only.

Retina: light energy initiates nerve impulses.

Cone cells: detect colored light.

Rod cells: Black and white vision.

Optic nerves: transmit nerve impulses to the brain.

Blind spot: Lacks retina, no vision at this point.

Vitreous humor: Refracts light, helps maintain shape.

Formation of images
The parts of the eye focus light rays onto the retina to produce a clear, inverted image.

The light initiates nerves impulses in the retina which travel to the brain via the optic nerve and which the brain interprets as color, shape, form and distance.

Long Sight
Long-sightedness is when the eye does not focus light on the retina (the light-sensitive layer at the back of the eye) properly. This may be because: the eyeball is too short. the cornea (transparent layer at the front of the eye) is too flat. the lens inside the eye is unable to focus properly.

Short Sight
Short-sightedness (myopia) usually occurs when the eyes grow slightly too long, which means they're unable to produce a clear image of objects in the distance.

Glaucoma
Glaucoma is a group of diseases that can damage the eye’s optic nerve and result in vision loss and blindness. Glaucoma occurs when the normal fluid pressure inside the eyes slowly rises.

Cataract
Cataract is a clouding of the eye’s lens and is the leading cause of blindness worldwide, and the leading cause of vision loss in the United States. Cataracts can occur at any age because of a variety of causes, and can be present at birth.

Amblyopia
Amblyopia, also referred to as “lazy eye,” is the most common cause of vision impairment in children. Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly.

Strabismus
Strabismus involves an imbalance in the positioning of the two eyes. Strabismus can cause the eyes to cross in (esotropia) or turn out (exotropia). Strabismus is caused by a lack of coordination between the eyes. As a result, the eyes look in different directions and do not focus simultaneously on a single point. In most cases of strabismus in children, the cause is unknown.

Pink eye (conjunctivitis)
This is the inflammation or infection of the transparent membrane that lines your eyelid and eyeball. It's characterized by redness and a gritty sensation in your eye, along with itching. Often a discharge forms a crust on your eyelashes during the night.

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