Refractive Surgery Glossary
The following are a few terms Dr. Cabler may use in his LASIK consultation:
ASTIGMATISM: The refractive error of the eye whose corneal surface curvature is out of round and shaped like a football such that both distance and near visions objects appear blurred and distorted.
CORNEA: The clear front of the globe that begins the process of focusing light the eye receives. The cornea is responsible for two-thirds of the eye's focusing power.
DIOPTER: The unit of measure of the power of a lens.
EPITHELIUM: The layer of cells that covers the outer surface of the cornea. During LASIK Surgery, the microkeratome makes a flap beneath the epithelium that is lifted so the laser can reshape the inner part of the cornea called the stroma.
HYPEROPIA: Also called farsightedness. The hyperopic eye is too short for its optical system. Light rays focus behind the retina and cause a blurriness of near objects and sometimes distance objects as well.
IRIS: The colored circle of the tissue that controls the amount of light entering the pupil by enlarging or reducing the size of the aperture (called the pupil).
KERATOCONOUS: A rare degenerative corneal disease in which the cornea thins and assumes the shape of a cone, seriously affecting vision. Prevents an individual from undergoing LASIK.
LASER: Light Amplification by Simulated Emission of Radiation. The excimer laser used in LASIK surgery operates in the ultraviolet wavelength. It produces a cool laser beam.
LENS: Part of the optical focusing system of the eye immediately behind the iris. As individuals age, the lens hardens. This causes individuals older than 40 years old to develop a condition called presbyopia in which reading fine print becomes more difficult without eyeglasses or contacts.
MICROKERATOME: The surgical instrument that creates the corneal flap to access the stroma for laser treatment. There are several FDA-approved microkeratomes on the market.
MYOPIA: Also called nearsightedness. The eye is too long for its optical system. The cornea is too steep therefore the light rays are focusing in front of the retina causing blurriness of distance objects.
PACHYMETER: An instrument that measures the distance between the corneal epithelium and corneal endothelium. A diagnostic test that helps make sure the corneas of potential LASIK patients are thick enough for LASIK surgery.
PRESBYOPIA: The progressive loss of the accommodative ability of the lens to focus. Part of the natural process of aging.
PUPIL: The opening in the center of the iris that enlarges (admitting more light) and reduces (admitting less light). A patient's whose pupils enlarge too much may experience nighttime glare. This is why Dr. Cabler will measure the pupil's enlargement capabilities. Individuals with this condition may still have LASIK, but may experience some nighttime glare because the LASIK treatment zone is smaller than the pupil's enlargement capabilities.
RADIAL KERATOTOMY: An earlier type of refractive surgery in which radial incisions were made in the cornea to flatten its curvature and reduce nearsightedness. Also known as RK. Today's LASIK lasers are much more precise in their reshaping of the cornea instead of relying on these type incisions.
REFRACTION: In eye care, the process of measuring a patient's refractive error and the clinical judgment to determine the optical correction needed.
REFRACTIVE ERROR: A nonpathologic deficiency in the eye's optical system.
REFRACTIVE SURGERY: A type of surgery that changes the refractive state of the eye.
RETINA: The inner lining of the eyeball; consists of a layer of light-sensitive cells that convert images from the optical system into electric impulses sent along the optic nerve for transmission to the brain.
SNELLEN ACUITY TEST: A measurement of visual acuity by testing the ability to read characters at a standard distance on a special target called the Snellen Chart.
SNELLEN CHART: A printed visual acuity chart consisting of Snellen optotypes - specially formed letters of the alphabet arranged in rows of decreasing letter size.
Also known informally as an eye chart.