B
B Scan
Ultrasonic procedure used to check for abnormalities or locate foreign bodies within the eye.
Barraquer Cyro-Lathe
An instrument used in performing refractive surgery to correct extreme myopia (nearsighted, shortsighted vision) or hyperopia (farsighted, longsighted vision).
Basement Membrane
A membrane of tissue beneath the epithelium that helps adhere the epithelium to the Bowman's layer or stromal tissue.
Bausch & Lomb
Ophthalmic equipment company.
BCVA
See Best Corrected Visual Acuity.
Best Corrected Visual Acuity
This is a measure of best acuity while wearing corrective lenses like glasses or contact lenses.
Bifocals
Corrective lenses that have two powers of correction. Typically the majority of the lens is corrected for distance vision while a small are is corrected for near vision. Bifocals and trifocals are normally prescribed for individuals with presbyopia.
Binocular
Both eyes.
Binocular Vision
The blending of the separate images seen by each of two eyes into a single image. Normal binocular vision yields a stereoscopic image and parallax-induced depth perception.
Black Box Laser
Common term used for a laser built by its owner or by a firm not approved by the FDA. Detailed Information Regarding Counterfeit Lasik Lasers
Blepharitis
A chronic or long term inflammation of the eyelids and eyelashes, affecting people of all ages. Among the most common causes are poor eyelid hygiene; excess oil produced by the glands in the eyelids; a bacterial infection; or an allergic reaction. Detailed Information Regarding Lasik and Blepharitis
Blind Spot
(1) A small area of the retina where the optic nerve enters the eye; occurs normally in all eyes.
(2) Any gap in the visual field corresponding to an area of the retina where no visual cells are present. Associated with eye disease.
Board Certified
See American Board of Ophthalmology.
Bowman's Layer
A layer of cells in the cornea. between the epithelium and stroma. The Bowman's layer appears to be without specific purpose.
Broadbeam
This is a method of applying excimer laser energy. A beam of energy is applied across the entire ablation zone at one time. See also variable beam and flying spot.
Buttonhole Flap
A complication of Lasik caused when the microkeratome breaks through the top of the cornea while creating a flap of corneal tissue. See Lasik Buttonhole Flap
C
CrossLinking
See Corneal Collagen Crosslinking with Riboflavin
C-CAP
See Custom Contoured Ablation Pattern
Calhoun Vision
Manufacturer of light adjustable intraocular lens. Detailed Information Regarding Calhoun Light Adjustable Lens
Canthus
Demarcation between the sclera and nasal corner of the eye.
Cataract
Also known as nuclear sclerosis. Cataracts are an opacity or clouding of the natural crystalline lens that may prevent a clear image from forming on the retina. Cataracts occur naturally and can be induced by trauma. The cataractous lens may require surgical removal if visual loss becomes significant, with lost optical power replaced with an intraocular lens.
Central Ablation Zone
See Optical Ablation Zone.
Central Island
A complication of excimer laser assisted refractive surgery where the laser fails to remove a portion of cornea. If one views the concave area of the ablation like a lake, one can imagine an island sticking up in the center. Visual symptoms are typically monocular diplopia or distortion. Detailed Information Regarding Lasik Central Islands
Central Retinal Artery
The blood vessel that carries blood into eye; supplies nutrition to the retina.
Central Retinal Vein
The blood vessel that carries blood from the retina.
Central Vision
See visual acuity.
Chiron
Ophthalmic equipment company. Click here to go to website.
Choroid
The layer filled with blood vessels that nourishes the retina; part of the uvea.
Ciliary Muscles
The muscles that relax the zonules to enable the crystalline lens to change shape for focusing.
Ciliary Processes
The extensions or projections of the ciliary body that secrete aqueous humor.
CK
See Conductive Keratoplasty
CLAPIKS
See Contact Lens Assisted Pharmacologically Induced Kerato Steepening
CLE
See Refractive Lens Exchange.
Clear Lens Exchange
See Refractive Lens Exchange
Clear Lens Replacement
See Refractive Lens Exchange
Clinical Trial
An investigative process under the jurisdiction of the FDA whereby device or medicine manufacturers sponsor experiments on people for the purpose of proving or disproving that the device or medicine performs as expected.
CLR
See Refractive Lens Exchange.
COAS
See Complete Ophthalmic Analysis System
Coherent Medical Group
Ophthalmic equipment company. 
Collarette
Color ring around the pupil.
Color Vision
The ability to perceive differences in color, including hue, saturation and brightness.
Comanagement
When two or more medical providers provide care to a patient. In refractive surgery it is common for an optometrist to provide preoperative testing and postoperative care with an ophthalmologist providing only the surgery.
Complete Ophthalmic Analysis System
An integration of WaveFront Sciences’ wavefront technology with Asclepion excimer laser system. The manufacturers say COAS will enable improved visual acuity in persons with vision defects
Complex Wavefront Retreatment
A secondary surgery using wavefront-guided ablation in an attempt to reduce higher order aberrations induced by previous surgery. Complex Wavefront Retreatment is an off-label use of the excimer laser.
Concave Lens
A lens with a hollow shape like the inside surface of a ball. Concave lenses are minus power lenses and are used to correct myopia (nearsighted, shortsighted vision).
Conductive Keratoplasty
A refractive surgery procedure for hyperopia and astigmatism that uses a probe to apply high frequency radio waves into the corneal tissue, causing shrinkage. This controlled shrinkage will reshape the cornea to accommodate refractive error. Detailed NearVision Conductive Keratoplasty (CK) Information
Cone Cells
One type of specialized light sensitive cells (photoreceptors) in the retina that provides sharp central vision and color vision. Also, see rods.
Conformer
Plastic or silicone shell usually inserted after eye removal to help form the socket and support the eyelids.
Conjunctiva
The thin transparent mucous membrane that lines the inner surface of the eyelid and covers the white surface of the eye.
Conjunctivitis
Inflammation of the conjunctiva. May be caused by bacteria, virus, allergens, or chemical or ultraviolet light exposure.
Contact Lens
Lens made of glass or plastic designed to maintain contact on the surface of the cornea. Usually used to correct refractive error.
Contact Lens Assisted Pharmacologically Induced Kerato Steepening
A process of accommodating hyperopic overcorrection following Lasik, PRK and RK, by molding the cornea with a tight fitting contact lens and nonsteroidal anti-inflammatory drugs. Detailed CLAPIKS After Lasik Information
Contact Lens Disinfectant
An agent that kills surface bacteria and microorganisms on contact lenses.
Contact Lens, Daily Wear
Contact lenses designed to be worn only during waking hours. Frequent & planned replacement contact lenses general term used to refer to contact lens regimens in which lenses are replaced on a planned schedule, either every two weeks, monthly or quarterly.
Contact Lens, Disposable
Contact lenses defined by the U.S. Food and Drug Administration as a contact lens that is used one time and discarded. These can be worn either for a single day or up to seven days, depending on wear schedule prescribed by the eye care professional. Any lens that is intended to be removed from the eye, cleaned, rinsed, disinfected, and reinserted does not qualify for inclusion in this category.
Contact Lens, Extended Wear
Contact lenses designed to be worn around-the-clock for intervals of one to seven days.
Contact Lens, Therapeutic
Contact lenses designed to aid in protecting and helping a sick eye to heal. These unique lenses are frequently combined with precise medication delivery schedules to heal the eye.
Contact Lens, Toric
Contact lenses designed to correct astigmatic refractive errors. Toric lenses are weighted to maintain a specific axis across the cornea.
Contrast Sensitivity
The ability to perceive differences between an object and its background.
Convergence/Divergence
The turning of the eyes inward/outward so that they are both "aimed" toward the object being viewed.
Convex Lens
A lens with a bulging surface like the outer surface of a ball. Convex lenses are plus power lenses and are used to correct hyperopia or farsightedness. Also used for reading glasses as required for presbyopia.
Cornea
The outer, transparent, dome-like structure that covers the iris, pupil, and anterior chamber. The cornea provides approximately two-thirds of the optical power of the eye. Light passes into the eye through the cornea allowing vision. Light also passes out of the eye allowing the iris and pupil of the eye to be seen. The cornea can be considered to have five layers:
1. Corneal epithelium
2. Bowman's layer
3. Corneal stroma
4. Descemet's layer
5. Corneal endothelium.
Corneal Abrasion
A scratch or similar trauma to the outer surface of the cornea. Detailed Lasik Corneal Abrasion Information
Corneal Collagen Crosslinking with Riboflavin
Used as a therapeutic treatment for keratoconus and corneas that have become unstable or weak due to ectasia, Corneal Collagen Crosslinking with Riboflavin (CrossLinking) is a technique where the eye is flooded with a riboflavin solution and exposed to ultra high frequency light. CrossLinking causes the collagen fibrils to thicken, stiffen, and reattach to each other, making the cornea stronger and more stable. Detailed CrossLinking For Keratoconus Information
Corneal Endothelial Cell Dystrophy
Also known as Fuch's Dystrophy, a progressive hereditary disease when moisture in the cornea is unable to evaporate properly, sometimes causing distortion of the cornea, irregular refractive error, and epithelial blisters. Detailed Corneal Endothelial Cell Dystrophy Information
Corneal Haze
When the cornea becomes cloudy with opaque white cells, creating vision that is similar to looking through fog.
Corneal Refractive Therapy
A temporary non-surgical process of wearing rigid gas permeable contact lenses in an attempt to reshape the cornea and reduce the need for corrective lenses. Essentially orthokeratology.
Corneal Remodeling
The healing of a wound of the cornea.
Corneal Topographical Map
A map of the corneal topography that shows the surface profile of the cornea.
Corneal Topography
A process of mapping the surface details of the cornea with a unique camera/computer combination.
Council for Refractive Surgery Quality Assurance
A nonprofit consumer/patient organization that certifies refractive surgeons based upon refractive surgery outcomes and educates the public about refractive surgery issues.
Credentials
In the healthcare industry credentials means the education, licensure, and professional history of a healthcare provider.
CRSQA
See Council for Refractive Surgery Quality Assurance. Pronounced "SURS-kah".
CRT
See Corneal Refractive Therapy
CrystaLens
An intraocular lens that is designed to change focus from distant to near objects. It is the first of its kind to achieve FDA approval. Details
Crystalline Lens
The natural lens of the eye, located behind the iris, which helps bring rays of light to focus on the retina. The original state of the lens is transparent, but the lens becomes cloudy with age (cataract). The lens has the ability to vary its power to accommodatively focus light from objects closer than optical infinity.
Custom Contoured Ablation Pattern
The customization of laser vision correction treatments for decentered ablations and similar corneal aberrations. The Food and Drug Administration has approved the use of Custom Contoured Ablation Pattern (C-CAP) method under a Humanitarian Device Exemption.

C-CAP uses a liquid material that is applied to the outside of the eye. In some cases, a contact lens is applied over the liquid to give a smooth surface. The liquid becomes more firm, and the contact (if used) is removed. A broadbeam laser applies energy to the entire treatment area with each pulse. The liquid ablates at the same rate as corneal tissue. As the laser removes tissue and the liquid, the high areas of the cornea are exposed and ablated down to the lowest areas. C-CAP has been shown to resolve many topographical imperfections caused by disease, trauma, or surgery.

Custom Cornea
The trade name for the use of a wavefront guided custom ablation with the LADARVision excimer laser built by Alcon. Custom Wavefront Lasik Detailed Information.
CustomVue
The trade name for the use of wavefront guided custom ablation with the VISX S4 excimer laser. Custom Wavefront Lasik Detailed Information.
CWR
See Complex Wavefront Retreatment
Cyclopegic Refraction
An examination of the eye to determine refractive error while the natural crystalline lens of the eye is paralyzed and unable to accommodate.
Cyclorotation
See Cyclotorsion.
Cyclotorsion
When eyes rotate clockwise or counterclockwise. This often occurs when a person changes from vertical (standing or sitting up) to horizontal (lying down) position.