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Glossary of Eye Terms

A scan: Ultrasonic procedure to measure specific areas within the eye.

Acuity: The clarity of vision, usually measured on a chart.

Anesthesia: Standard cataract surgery anesthetic is a local anesthetic that blocks the optic nerve. The anesthesia is administered by injection and is painless. The patient is awake during surgery but may be sedated.

Astigmatism: A warping of the curvature of the cornea so that light rays entering the eye do not meet in a single focal point, resulting in a distorted image.

B scan: Ultrasonic procedure used to check for abnormalities or locate foreign bodies within the eye.

Cataract: A disease which causes the lens or its capsule to become opaque. It can result in partially or severely decreased vision, but is usually removable and vision correctable by use of an implant.

Cornea: The clear front surface of the eye which covers the iris and pupil. Acts like the lens of a camera.

Diopter: A unit of measure of the refractive power of a lens, equal to the power of a lens with focal distance of one meter.

Glaucoma: A disease characterized by increased pressure within the eyeball, leading to gradual vision impairment and sometimes, blindness if not diagnosed and treated.

Hyperopia: Farsightedness; a condition in which light rays are focused behind the retina so that distant objects are seen more clearly than near ones.

Intacs: Intacs are tiny plastic ring segments that are implanted in the cornea to correct refractive error.

Intraocular lens implantation: Surgery to replace a cloudy lens (cataract) with a new, clear, artificial lens designed to eliminate the need for very thick, heavy glasses. This is usually done at the time of cataract extraction but may be done later as a secondary implant.

Keratometry: The measurement of the curvature of the cornea.

Keratomileusis: A surgical procedure for treating farsightedness and nearsightedness. A thin layer of the cornea is removed and reshaped, becoming a natural contact lens, and then permanently repositioned on the cornea.

Myopia: Nearsightedness; a condition in which light rays from distant objects are focused in front of the retina instead of on it, so that distant objects are not seen clearly.

Phacoemulsification: Use of ultrasonic vibration to shatter and break up a cataract, making it easier to remove.

Radial keratotomy: A surgical procedure for treating nearsightedness in which the cornea is flattened by means of a series of radial cuts on it.

Retina: A layer of cells at the back of the eye which are sensitive to light and upon which the image formed by the lens is focused. The image is then carried to the brain by the optic nerve.

Secondary Implant: If no lens was placed in the eye at the time of initial cataract removal surgery, then a secondary procedure to implant a lens may be done months or year later.

Slit Lamp: A microscope using various magnifications combined with a strong light that can be focused into a slit for examining the eye.

Tonometry: The measurement of the tension or pressure inside the eyeball.

Ultrasound (A & B Scan): A procedure using sound waves to measure certain portions or detect abnormalities within the eye.

Visual Field: A measurement of the vision level in all portions of the field of vision.