Ablate
In surgery, to remove

Ablation
Removal of tissue with the excimer laser

Ablation Zone
Area of tissue that is removed during laser surgery

Acuity
Clearness or sharpness of vision

Astigmatism
A defect of vision in which the image of an object is distorted, usually due to a football-shaped curvature of the cornea.

Automated Lamellar Keratoplasty (ALK)
A refractive surgery procedure for patients with high nearsightedness where a "pancake" of corneal tissue is removed with a microkeratome.

Cornea
The transparent circular part of the front of the eyeball. It refracts the light entering the eye to focus it onto the retina.

Corneal Topography
A computer-generated map of the surface curvature of the cornea.

Corneal Transplantation
A diseased or scarred cornea is replaced with a healthy cornea.

Diopter
Tthe measurement of refractive error; a negative diopter signifies an eye with myopia (nearsightedness), a positive diopter signifies an eye with hyperopia (farsightedness)

Endothelium
Layer of cells on the inside surface of the cornea

Epithelium
Outermost layer of cells of the cornea and the eye's first defense against infection

Glare
Complication of refractive surgery in which scatter from bright light decreases vision

Halo
Complication of refractive surgery in which patient sees rings around lights due to optical imperfections in or in front of the eye

Hyperopia
Farsightedness.

In Situ
A Latin term meaning "in place" or not removed

Iris
The colored part of the eye; suspended behind the cornea and immediately in front of the lens

Keratectomy
Surgical removal of corneal tissue

Keratotomy
Surgical incision of the cornea

Keratitis
Inflammation of the cornea

Kerato
Prefix indicating relationship to the cornea

Keratoconus
Rare, inherited disorder characterized by an irregular corneal surface (cone-shaped) resulting in blurred and distorted images

Keratomileusis
Surgical reshaping of the cornea

Keratoplasty
Replacement of the cornea

Laser Correction of Nearsightedness
Vision is corrected or improved with an excimer laser, which uses a very thin beam of light of high energy to sculpt small amounts of tissue from the corneal surface, also called photorefractive keratectomy (PRK) or LASIK.

LASIK
LASIK refers to Laser In Situ Keratomileusis. After a "pancake" of corneal tissue is prepared and folded back, the excimer laser is used to sculpt a small amount of corneal tissue to correct nearsightedness.

Lens
Part of the eye that changes shape, allowing the eye to focus at different distances

Microkeratome
Instrument a surgeon uses to create the corneal flap in the uppermost layer of the cornea during the LASIK procedure

Monovision
Purposeful adjustment of dominant eye for distance vision and the other for near vision

Myopia
Nearsightedness.

Nomogram
Surgeon's adjustment to the laser's computer calculation to further refine results

Overcorrection
Complication of refractive surgery where the desired amount of correction exceeds attempted results

Phototherapeutic Keratectomy (PTK)
An excimer laser treatment for patients with diseases of the cornea, corneal dysfunction, abnormalities, or scarring.

Photorefractive Keratectomy (PRK)
Another term for laser correction of nearsightedness.

PRK
Procedure involving the removal of the surface layer of the cornea (epithelium) by gentle scraping and use of a computer controlled excimer laser to reshape the stroma

Presbyopia
Age related inability to focus on near objects due to reduced elasticity of the lens; usually begins to surface between ages 40-45

Pupil
Hole in the center of the iris that changes size in response to changes in lighting

Radial and Astigmatic Keratectomy (RK and AK)
Radial incisions on the surface of the cornea correct nearsightedness; arcuate incisions are used to correct astigmatism.

Refraction
The change in the direction of light rays when they pass from one transparent medium to another of a different density. Errors in refraction occur when light rays do not come to a focus on the retina due to curvature of the cornea or lens, causing nearsightedness, farsightedness, or astigmatism.

Refractive Errors
Hyperopia, myopia and astigmatism

Retina
Layer of fine sensory tissue that lines the inside wall of the eye; captures images, much like film in a camera, and transforms images into electrical signals and sends to brain

Retreatment
A secondary refractive procedure performed after the initial one in an attempt to achieve better visual acuity

Sclera
Tough, white, outer layer (coat) of the eyeball that , along with the cornea, protects the eyeball

Stroma
The middle, thickest layer of tissue in the cornea

Undercorrection
Complication of refractive surgery where the desired amount of correction is not fully achieved

Visual acuity
Clearness of vision; ability to distinguish details and shapes