Glossary

Serving the Greater Los Angeles Area

Coming from: Beverly Hills, Santa Monica, Pasadena, Orange County, Ventura County

Ablate: To remove, or vaporize, tissue using laser energy.

Ablation zone: The area of tissue removed by the laser. Also called the treatment zone.

Accommodation: The ability of the eye’s lens to fine-tune focus by flexing, becoming more convex or more concave, as needed. Accommodation can compensate for minor focusing problems in younger people whose lens and surrounding muscles are still limber and pliable.

Antibiotic drops: Eyedrops containing medicine that prevents infection by killing or inhibiting harmful bacteria.

Anti-inflammatory drops: Eyedrops containing medicine that counteracts inflammation, which is characterized by redness, heat, pain, and swelling.

Artificial tears: Sterile, nonpreserved eyedrops used to lubricate the eyes the same way tears do.

Astigmatism: A refractive error caused by an asymmetrically shaped cornea. Rather than being spherical in shape, the cornea is shaped like a football, causing light to come to several points of focus instead of meeting at a single point of focus. People with astigmatism experience blurred images or double vision.

Automated lamellar keratoplasty (ALK): An older refractive surgery, developed in 1987, in which the surgeon first creates an extremely thin flap in the uppermost layer of the cornea using a device called a microkeratome, then makes a second pass with the microkeratome to remove additional tissue.

Axis: A measurement of astigmatism, the axis (a line) is the symmetrical center of a curved optical surface.

Benchmarking: The process of tracking statistical outcomes for the purpose of predicting future outcomes. With LASIK eye surgery, statistics from 1,000 or more procedures can provide a good basis for benchmarking.

Best corrected vision: The best possible vision achieved with corrective lenses.

Blended vision: See monovision.

Board-certified: Physicians who have undergone the additional education, internships, residencies, and examinations required for certification.

Cataract: Clouding of the lens within the eye causing decreased vision.

Central island: A treatable complication from LASIK in which a small raised area in the center of the cornea’s treatment zone results from having received less laser energy than the surrounding tissue. Central islands can cause distorted vision.

Central lamellar keratitis (CLK): An inflammation on the cornea between the corneal flap and the stroma. This rare complication of LASIK eye surgery is characterized by small deposits under the corneal flap that can sometimes damage the underlying stroma enough to affect vision and require an enhancement procedure.

Constrict: To become smaller.

Cornea: The outer, dome-shaped, transparent part of the eye that bulges out at the front of the eyeball and covers the iris and pupil. Its curvature causes light to bend. The cornea provides most of the eye’s focusing power. It is the only part of the eye on which LASIK is performed.

Corneal topographer: An instrument that creates a three-dimensional map of the cornea using computerized analysis.

Cryolathe: A mechanical lathe used to grind a frozen corneal disc into a new shape before it is replaced on the eye.

Crystalline lens: See lens.

Cylinder: One of three measures in an eyeglass prescription. It indicates whether astigmatism is present, and to what degree.

Diffuse lamellar keratitis (DLK): A potential complication of LASIK, also known as “sands of the Sahara” syndrome. DLK is a noninfectious inflammation that arises between the corneal flap and the underlying stroma.

Dilate: To become larger, as when the pupil enlarges in very dim light conditions.

Diopter: A measurement of refractive error. Hyperopia is measured in terms of positive diopters. Myopia is measured in terms of negative diopters.

Disease neutral: Something that neither prevents diseases nor affects the treatment of diseases. LASIK eye surgery is considered disease neutral.

Dry eye: A condition characterized by corneal dryness due to inadequate tear production.

Endothelium: The innermost layer of the cornea, a single cell thick, that helps regulate the cornea’s hydration.

Enhancement procedure: A secondary treatment with the excimer laser to fine-tune one’s visual acuity after the initial LASIK procedure. Enhancements take place after vision has stabilized, usually two to three months after LASIK. Enhancements usually do not require making a new corneal flap.

Epithelial ingrowth: A potential complication of LASIK eye surgery produced when corneal surface cells, or epithelium, grow underneath the corneal flap during the first month following surgery. The condition is often easily diagnosed and treated.

Epithelium: The thin, protective, outermost surface of the cornea. It is made up of the same kind of cells that cover most of the body. The epithelium grows rapidly and continually regenerates.

Excimer laser: The type of laser used in refractive surgery to remove corneal tissue. It emits highly precise pulses of ultraviolet light to break up tissue, one molecular layer at a time, vaporizing it without generating heat that could damage surrounding tissue.

Eyelid speculum: A device placed between the upper and lower eyelids to keep the patient from blinking.

Ghosting: The appearance of double images or shadows around images. Ghosting is sometimes experienced by people with astigmatism, and can also result from irregular healing of the corneal surface after LASIK.

Glaucoma: A disorder of the eye characterized by an increase of pressure within the eyeball.

Halo: A complication of LASIK in which the patient sees additional rings around lights at night. Halos often decrease with time.

Haze: Scarring of the corneal stroma, or corneal bed. Significant haze is an extremely rare complication of LASIK surgery.

Herpes simplex: A recurrent viral infection of the eye characterized by a painful sore on the eyelid or surface of the eye. It causes inflammation of the cornea and can lead to blindness.

Hyperopia: Also known as farsightedness, hyperopia occurs when the eyeball is too short from front to back, or the eye’s focusing mechanism is too weak, causing light rays to be focused behind, rather than on, the retina. People with hyperopia see objects at a distance more clearly than close up, but may have difficulty with both.

Induced astigmatism: A rare complication of LASIK eye surgery in which astigmatism develops after the initial surgery. Most people can tolerate a small degree of astigmatism. In more serious cases, induced astigmatism can be treated with an enhancement, if necessary.

Inflammation: A localized response to an injury that results in redness, heat, pain, and swelling, and can result in tissue damage if left untreated.

Informed consent: A legal form the patient will be asked to sign after thoroughly discussing the risks, benefits, alternative options, and possible complications of LASIK.

Intraocular pressure: The pressure exerted by the fluid within the eye that gives it its round, firm shape.

Iris: The colored ring of tissue in the eye that is behind the cornea and in front of the lens. The muscles of the iris can adjust the size of the opening, or pupil, to allow for larger or smaller amounts of light to enter the eye.

Keratectomy: Surgical removal of any part of the cornea. In the context of LASIK, keratectomy is the flap-making part of the procedure.

Keratomileusis: Any process of carving, or reshaping, the cornea.

Lamellar: An adjective meaning “layered.” Lamellar corneal surgery corrects focusing errors by removing or reshaping some of the corneal layers.

LASIK: An acronym for laser-assisted in situ keratomileusis. In LASIK eye surgery, a small instrument called a microkeratome creates an extremely thin, hinged flap on the surface of the cornea. After the flap is gently lifted back, the surgeon reshapes the corneal stroma using an excimer laser. The corneal flap is then replaced, and it quickly adheres. LASIK is a safe and pain-free form of refractive eye surgery that has proven to be highly successful and popular.

Latent hyperopia: An age-related phenomenon in which mild farsightedness increases after age thirty or forty.

Lens: The globe-shaped natural lens of the eye, located behind the iris, that helps fine-tune the angle of light to bring it to a point of focus on the retina. As the lens becomes less flexible with age, its ability to refine focus gradually decreases.

Microkeratome: The instrument a surgeon uses to create the corneal flap in the uppermost layer of the cornea during the LASIK eye surgery procedure.

Monovision: A process by which the surgeon corrects one’s dominant eye for seeing at a distance and one’s nondominant eye for seeing objects close up.

Myopia: Also known as nearsightedness, myopia is due to a cornea that has too much curvature, or an eyeball that is too long, causing light to be focused in front of, rather than on, the retina. People with myopia have difficulty seeing objects at a distance.

Nomogram: The surgeon’s formula entered into the laser’s computer calculation to further refine the manufacturer’s recommended settings.

Nonfreeze keratomileusis: A process of reshaping the corneal disc directly on the eye without having to remove the disc and freeze it for the purpose of reshaping, as was done in early lamellar surgeries, precursors to LASIK surgery.

Ophthalmology: The field of science dealing with diseases and conditions of the eye.

Ophthalmologist: A medical doctor specializing in the diagnosis and medical or surgical treatment of eye diseases.

Optic nerve: A bundle of nerve fibers, about the diameter of a pencil, that connects to the nerve fiber layer of the retina and terminates in the brain. The optic nerve carries the visual messages from the photoreceptors of the retina to the brain, where images are created and processed.

Optometrist: An eye-care professional specializing in the examination, diagnosis, treatment, management, and prevention of diseases and disorders of the eye.

Orthokeratology: A technique for treating myopia using a series of rigid contact lenses to reshape the cornea. The lenses apply pressure to the sides of the cornea, flattening them.

Overcorrection: A complication of LASIK eye surgery, overcorrection results when the amount of correction resulting from the LASIK procedure is more than intended.

Peripheral vision: The ability to see objects and movement outside of, or on the periphery of, one’s direct line of vision.

Photoablation: The process of removing, or vaporizing, tissue by means of laser energy.

Photorefractive keratectomy (PRK): A type of laser vision correction that reshapes the cornea by ablating, or vaporizing, the corneal tissue one microscopic layer at a time using an excimer laser. Unlike LASIK, in which a hinged corneal flap is first made and lifted back, exposing the corneal bed, the sculpting process used in PRK removes the outer (epithelial) layer of the cornea as the laser energy works its way down to the corneal bed.

Presbyopia: Often confused with farsightedness, presbyopia (literally, “old eyes”) is the age-dependent need for reading glasses or bifocals, caused by the decreasing ability of the eye’s lens and surrounding muscles to fine-tune focus.

Punctum plugs: Used in the treatment of dry eye, these tiny silicone plugs are inserted into the tear-drainage openings of one’s eyelid to delay the drainage of natural tears so the eyes will stay moist.

Pupil: The small black dot, or opening, in the center of the iris. The pupil changes its diameter in response to changes in lighting.

Radial keratotomy (RK): A form of refractive surgery in which the eye surgeon alters the shape of the cornea by making thin incisions around the cornea in a spoke-like pattern. The incisions cause the central portion of the cornea to flatten, treating myopia and astigmatism.

Refract: To bend, as when light passes through a curved shape such as a cornea or lens.

Refractive error: The degree to which one’s eye is able to refract, or bend, light. People with refractive errors (focusing problems) are nearsighted or farsighted, and may have astigmatism as well.

Refractive surgery: Any type of surgery that changes the focusing power of the eye in order to correct a refractive error. LASIK eye surgery is a type of refractive surgery that corrects the eye’s focusing ability by reshaping the curvature of the cornea.

Regression: A potential complication of LASIK eye surgery in which the eye tends to drift back, or regress, toward its original refractive error.

Retina: The light-sensitive layer of cells on the inner back surface of the eye that processes light and functions much like film in a camera. The retina converts light into electrical impulses that are transmitted along the optic nerve to the brain, which interprets the impulses as images.

Sclera: The tough “white” of the eye that makes up five-sixths of the outer layer of the eyeball. Along with the cornea, it protects the eyeball.

Snellen eye chart: The standard eye chart used by optometrists and ophthalmologists to determine visual acuity.

Sphere: One of three measurements taken during an eye examination to arrive at one’s eyeglass prescription. The sphere measures where the eye focuses light—on the retina (normal vision) in front of the retina (myopia), or behind the retina (hyperopia).

Starburst: A visual aberration in which the patient sees rays radiating from lights viewed at night. Starbursts may be seen by people who wear eyeglasses and contact lenses, and are sometimes experienced by patients who have undergone LASIK.

Striae: Wrinkles or folds in the corneal flap that are a potential complication of LASIK eye surgery. Striae can be smoothed out and corrected if treated early.

Stroma: The strong, fibrous layer that makes up 90 percent of the cornea’s thickness and provides the cornea with its structure and shape. Also called the stromal bed, this is the part of the cornea sculpted with the laser in LASIK surgery.

Tonometry: A procedure for measuring intraocular pressure, or the pressure inside the eye.

Topical corticosteroid: A medicated eye drop that prevents inflammation of the eye tissue following LASIK surgery.

Undercorrection: A complication of LASIK, undercorrection results when the amount of correction resulting from the LASIK eye surgery procedure is less than intended. Most undercorrections can be treated with an enhancement procedure.

Visual acuity: The sharpness or clarity of vision that enables one to distinguish fine details and shapes.

Vitreous humor: The gel-like substance, composed of about 99 percent water, that fills the main cavity of the eye between the lens and the retinal wall.