ACUITY- Measure of an eye's ability to distinguish object details and shape. Usually specified by the smallest identifiable object that can be seen at 20 ft. for distance vision and 16 in. for near vision.
AMBLYOPIA - also referred to as "lazy eye." Decreased vision in one or both eyes without detectable anatomic damage in the eye. Usually correctable with eyeglasses.
ARMD - see Macular Degeneration
ASTIGMATISM - Irregular shape of the cornea causing light rays to scatter at different points of focus, blurring near and distant vision. In most cases of astigmatism, the cornea is shaped like the surface of a football - more steeply curved in one area.
BLEPHEROPLASTY - surgical procedure used to treat drooping eyelids or excessive eyelid folds (also known as dermatochalasis).
CONTRAST SENSITIVITY - Ability of the eye to detect detail of an object against a low contrast background (i.e. Black car crossing road at night or a white rabbit in the snow). Contrast sensitivity is a more sensitive measure of vision than acuity.
CORNEA - Transparent outer covering of the eye that covers the iris, pupil and anterior chamber and provides most of an eye's focussing power.
DERMATOCHALASIS - Excess eyelid skin caused by atrophy of the elastic tissue. A fold of tissue from the upper lid usually hangs over the eyelid margin. Can be corrected with a blepharoplasty.
DIOPTERS - Unit of measure to designate the refractive power of a lens (i.e. a 1 diopter lens focuses light at 1 meter or 40 inches of focusing power).
ECTOPIC - Displaced from its normal position. Ectopic macula or ectopic pupil.
ECTROPION - Outward turning of upper or lower eyelid causing the lid to fall or pull away from the eyeball.
ENHANCEMENT - Fine-tuning of the original LASIK procedure to obtain best visual outcome. Enhancement treatments are usually performed 3 months following the original procedure after the eye has stabilized completely. Until the corneas have healed, final vision cannot be determined. Patients are encouraged to wait until their doctor has confirmed visual stability before considering an enhancement.
ENTROPION - Inward turning of upper or lower eyelid causing the lid margin to rest against the eyeball, causing irritation to the surface of the eye.
EPITHELIAL CELLS - Make up one of the 5 layers of the cornea (epithelium), whose function is to cover nerve endings and protect the cornea from injury. The corneal epithelium is analagous to skin cells elsewhere on the body.
EXCIMER LASER - Non-thermal "cool" unltraviolet laser (argon-flouride type) used for LASIK surgery. The laser is capable of etching or reshaping corneal tissue with great precision.
FDA - (Food and Drug Administration) - The federal agency that regulates the marketing of drugs and devices and determines their safety and effectiveness prior to approved use by the consumer.
FLAP - A thin protective layer (about 1/4 to 1/3 thickness) of corneal tissue created by the microkeratome.
FOVEA - Center area of retina producing sharpest vision.
HYPEROPIA - "Farsightedness" due to the eyeball being too short/flat or the refractive powers of the cornea and lens too weak. Light rays strike the retina before they come to focus, resulting in blurred images of near objects.
HRT - The Heidelberg Retina Tomograph II is used to detect glaucoma quickly, painlessly and without dilation. The HRT is a diagnostic laser that generates a precise and comprehensive analysis of the optic nerve.
IRIS - Tissue behind the cornea that gives color to the eye (i.e. blue eyes) and controls amount of light entering the eye by varying the size of its central opening (pupil).
IRREGULAR ASTIGMATISM - Irregular or warped shape to the cornea resulting in blurred or distorted images. Requires use of a gas permeable contact lens or specialized laser treatment to correct.
LACRIMAL DUCT - Tear drainage channel that extends from the lacrimal sac to an opening in the mucous membrane of the nose. Can become obstructed with blocked tears causing excessive tearing to over-compensate for the new dryness.
LASIK - "Laser Assisted in-Situ Keratomileusis" uses a microkeratome to first create a thin flap on the cornea. An Excimer laser is then used to sculpt the underlying cornea into a new shape to correct refractive errors.
LENS - Transparent biconvex tissue within the eye that helps bring rays of light to focus on the retina. The lens crystalline can change shape and increase the optical power of the eye when viewing near objects. This ability to accommodate is lost after age 40, requiring the use of bifocals or reading glasses.
MACULAR DEGENERATION - also known as Age-Related Macular Degeneration - characterized by a change in the central vision as spots appear on the eye's macula. Can be "dry" (atrophic) version or "wet" (choroidal neovascularization) version. Laser treatments are used to prevent or lessen severe loss of vision.
MICROKERATOME - Automated surgical instrument used to create a thin protective flap of corneal tissue in LASIK.
MONOVISION - A treatment strategy used for people with presbyopia that corrects vision in one eye for distance while leaving the fellow eye as is for viewing near objects. Refractive surgery patients over 40 may choose monovision in order to aviod wearing corrective eyewear for distance or near.
MYOPIA - "Nearsightedness" due to the eyeball being too long/steep or the refractive powers of the cornea and lens too strong. Myopic patients may see near objects clearly, if at an appropriate distance, while more distant objects are blurred.
OPHTHALMOLOGIST - Medical specialist. A physician specializing in the diagnosis and treatment of refractive, medical and surgical problems related to eye diseases and disorders.
OPTIC NERVE - A sensory nerve that carries impulses for sight from the retina to the brain.
OPTOMETRIST - Vision Care Specialist who treats vision conditions and prescribes medications for certain eye diseases.
PRESBYOPIA - Loss of elasticity of the crystalline lens resulting in diminished power of accommodation. Occurs in the normal aging process, usually after age 45. Presbyopic patients loose the ability to vary the focussing power of their eyes and must use reading glasses or bifocals for near work.
PRK - "Photo-refractive Keratectomy" - A surgical procedure that uses a laser to vaporize a thin layer of outer corneal tissue, thus improving light refraction by the eye. PRK has been largely displaced by LASIK, because LASIK provides a faster recovery of vision, less discomfort and the ability to enhance or refine the outcome easily 3 months after surgery. However, certain patients may have special conditions, ( i.e. recurrent corneal erosions), which would make PRK a better option for them.
PTERYGIUM - Abnormal, wedge-shaped growth on the bulbar conjunctiva. May gradually advance onto the cornea and require surgical removal.
PTK - "Photo Keratectomy" - A surgical procedure using an excimer laser to remove corneal scars and smooth an irregular corneal surface.
PUPIL - Black circular opening in the center of the iris that regulates the amount of light that enters the eye, like the aperture of a camera.
REFRACTION – The Determination of an eye's refractive error and the best corrective lenses to be prescribed. The eye's prescription is measured in units of optical power called diopters.
REFRACTIVE ERROR - an error in the focusing of light by the eye and a frequent reason for reduced visual acuity.
RETINA - The vertebrate retina is a light sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses. These are sent to various visual centers of the brain through the fibers of the optic nerve.
RK - (Radial Keratotomy) - A surgical procedure that utilitzes a scalpel to make a calculated number of cuts (usually 4-8) on the surface of the eye in order to flatten and reshape the cornea, thus changing the point at which light focuses.
STRABISMUS - is a condition in which the eyes are not properly aligned with each other.[2] It typically involves a lack of coordination between the extraocular muscles that prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely affect depth perception. Strabismus can be either a disorder of the brain coordinating the eyes or a disorder of one or more muscles, as in any process that causes a dysfunction of the usual direction and power of the muscle or muscles.
TONOGRAPHY - Test used to determine how intraocular pressure responds to pressure on the eye, a factor that may indicate the presence of glaucoma.
TOPOGRAPHY - the description of such surface shapes and features. Often used to show the surface curvature of the cornea.
TRABECULECTOMY - a surgical procedure used in the treatment of glaucoma to relieve intraocular pressure by removing part of the eye's trabecular meshwork and adjacent structures. It is the most common glaucoma surgery performed and allows drainage of aqueous humor from within the eye to underneath the conjunctiva where it is absorbed. This outpatient procedure is most commonly performed under monitored anesthesia care in a half awake state using a retrobulbar block or a combination of topical and subtenon (Tenon's capsule) anesthesia.
VISUAL FIELD - The term is often used in optometry and ophthalmology, where a visual field test is used to determine whether the visual field is affected by diseases that cause local scotoma or a more extensive loss of vision or a reduction in sensitivity (threshold).