- Vision & Eye Care
Parts of the Eye
By Joan Whetzel
Human eyes work something like cameras. Light enters through the cornea, the clear part that acts much like the glass lens on a camera. The pupils control the amount of light, like a camera's shutter. The light is focused on the retina, much like it would focus on the film inside the camera. And then the optic nerves send the record of the image produced by the light to the brain. In a digital camera, the electronics would send those image records to the camera's memory. Each part of the eye's anatomy plays its part in the vision process and the functioning of the eye.
1. Aqueous Humor: The clear fluid contained in the anterior chamber of the eye. It nourishes the lens and cornea.
2. Choroid: A vascular membrane located between the sclera and retina, that is dark brown in color.
3. Ciliary Body: A thin, vascular, middle-layer in the eye between the sclera (the white) and retina (the nerve layer lining the back of the eye).
4. Conjunctiva: A moist membrane that is thin and clear. It covers the inner surface of the eyelid and outer surface of the eye. Conjunctivitis occurs when the eyelid and eye surface become inflamed due to infection, making the eye appear pink in color.
5. Cornea: The clear part of the eye covering the iris and pupil. It transmits the light into the eye and performs 70% of the eye's focusing ability.
6. Eyelid: A fold of skin that is moveable, thanks to an internal muscle that allows the lid to close for protecting and moistening the eye and to open allowing the light into the eye.
7. Eyelashes: Protect the eye by helping to keep out dust, debris and other foreign objects.
8. Iris: The colored part of the eye that controls the amount of light entering the eye by opening and closing the aperture. The iris lies behind the cornea.
9. Lacrimal Gland: A tinyalmond-shaped structure responsible for tear production, which keeps the eye from drying out.
10. Lens : A clear layer behind iris with the approximate thickness of 5dimes. Hundreds of microscopic fibers keep it suspended behind the iris. It is biconvex (i.e. a magnifying lens that is curved outward on both sides like a bean) which allows it to focus the light on the retina.
11. Lens Capsule: A membrane covering the lens something like cellophane, but much thinner.
12. Optic Nerves: The nerves at the back of the eye, that collect information from the light coming into the eye, and transfers that information from the eye to the brain.
13. Orbit: The bony cavity in the skull where the eyeball is held in place by muscles, which also controls eye movement back and forth, up and down, and in circular motions.
14. Pupil: The hole in the iris that gets smaller and larger in response to the amount of light coming into the eye. High light conditions cause the pupil to constrict (or close) and low light conditions allow the pupil to dilate (or open wider).
15. Retina: The layer of light sensitive nerve tissue at the back of the light that converts the optical images to electrical impulses before sending them to the brain by way of the optic nerves. A small spot in the center of the retina, called the macula, is the area where vision is the sharpest.
16. Uvea: The eye's vascular tissues which includes the iris, the ciliary body, and the choroid.
17. Vitreous Humor: The clear gelatinous fluid filling the 2/3 of the eyeball interior, helping to keep the retina attached.
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