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 Eyeglasses, Sunglasses, and Magnifiers Main Article |  Glossary |  Eyeglasses, Sunglasses, and Magnifiers Index 

Eyeglasses, Sunglasses, and Magnifying Glasses Glossary of Terms

The following are health and medical definitions of terms that appear in the Eyeglasses, Sunglasses, and Magnifying Glasses article.

Dilate: To stretch or enlarge. It comes from the Latin verb "dilatare" meaning "to enlarge or expand."

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.
See the entire definition of Eye

Lens: The transparent structure inside the eye that focuses light rays onto the retina (the nerve layer that lines the back of the eye, senses light and creates impulses that go through the optic nerve to the brain). The lens was named after the lentil bean because it resembled it in shape and size.
See the entire definition of Lens

Prescription: A physician's order for the preparation and administration of a drug or device for a patient. A prescription has several parts. They include the superscription or heading with the symbol "R" or "Rx", which stands for the word recipe (meaning, in Latin, to take); the inscription, which contains the names and quantities of the ingredients; the subscription or directions for compounding the drug; and the signature which is often preceded by the sign "s" standing for signa (Latin for mark), giving the directions to be marked on the container.

Pupil: The opening of the iris. The pupil may appear to open (dilate) and close (constrict) but it is really the iris that is the prime mover; the pupil is merely the absence of iris. The pupil determines how much light is let into the eye. Both pupils are usually of equal size. If they are not, that is termed anisocoria (from "a-", not + "iso", equal + "kore", pupil = not equal pupils).
See the entire definition of Pupil

Resistance: Opposition to something, or the ability to withstand it. For example, some forms of staphylococcus are resistant to treatment with antibiotics.
See the entire definition of Resistance

Rest: 1. Repose. Relaxation.
2. A fragment of embryonic tissue that has been retained after the period of embryonic development. Also called an embryonic rest.

Visual acuity: The clarity or clearness of the vision, a measure of how well a person sees. The ability to distinguish details and shapes of objects; also called central vision.
See the entire definition of Visual acuity back to top

 Eyeglasses, Sunglasses, and Magnifiers Main Article |  Glossary |  Eyeglasses, Sunglasses, and Magnifiers Index 




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Eyeglasses, Sunglasses, and Magnifying Glasses

What is the structure of the eye?

The eyes are complex sensory organs. About 85% of the total sensory input to our brains originates from our sense of sight, while the other 15% comes from the other four senses of hearing, smell, touch, and taste. The eyes are designed to optimize vision under conditions of varying light. Their location, on the outside of the face, makes them susceptible to trauma, environmental chemicals and particles, and infectious agents. The eyelids and the position of the eye within the bony orbital cavity are the major protective mechanism for the eye.

The eye itself has the shape of a sphere measuring about 1 inch in diameter. It consists of a clear, transparent dome at the front (the cornea) that is surrounded by the white of the eyeball (the sclera). The iris of the eye is the circular, colored portion within the eye, and behind the cornea, and the pupil is the central opening within the iris. Behind the iris and pupil is the e...

Read the Eye Care article »



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