Aberration: Distortions, related to astigmatism , that cause the inability of light rays entering the eye to converge (come together) to a single focus point on the retina . Aberration are divided into two main categories: higher-order and lower-order.
Ablation: Surgical removal of tissue, typically using a cool beam laser .
Ablation zone: The area of tissue that is removed during laser surgery.
Amblyopia: Dullness or obscurity of sight for no apparent organic reason, therefore not correctable with glasses or surgery. Sometimes called a lazy eye, wherein one eye becomes dependent on the other eye to focus, usually developed in early childhood. Often associated with strabismus .
Anisometropia: Condition of the eyes in which they have unequal refractive power .
Antioxidants: Micronutrients that destroy or neutralize free radicals, molecules that have been implicated as one causative factor in the stimulation of abnormal cellular reproduction (cancer) and cellular destruction (aging).
Aqueous humor: Transparent fluid occupying the anterior chamber and maintains eye pressure.
ARMD: age related macular degeneration: Destruction and loss of the photoreceptors in the macula region of the retina resulting in decreased central vision and, in advanced cases, blindness.
Astigmatic Keratotomy (AK): Treats astigmatism by flattening the cornea with arc-shaped incisions in its periphery, similar to RK.
Astigmatism: Structural defects of the eye in which the light rays from a viewed object do not meet in a single focal point, resulting in blurred images being sent to the brain. An astigmatic cornea is not perfectly rounded like a basketball but has an irregular shape more like the side of a football. Astigmatism is most often combined with myopia or hyperopia .
Automated Lamellar Keratoplasy (ALK): Procedure that predates LASIK eye surgery and is not generally used any more.
Automated perimeter: Computer-driven device used to plot defects in the visual field (peripheral vision or side vision). Usually, this is a large hemisphere shell into which the patient’s head is placed. Various points of lights, sometimes of different sizes, intensities and colors are projected onto the screen. The patient then indicates whether the light is seen and the response is recorded. The computer then plots the effective visual thresholds within the targeted visual field.
Axis: Optical – a straight line through the centers of both surfaces of a lens. Visual – a straight line from the object of vision to the fovea of the eye.
BCVA: Best corrected visual acuity.
Blind spot: The area of the optic disk where the optic nerve fibers exit the eye and where there are no light-sensitive cells. This small area can be measured and in glaucoma, as the nerve fibers die, the blind spot tends to enlarge and elongate. This is one of the diagnostic hallmarks of glaucoma.
Choroid membrane: Dark, vascular , thin skin-like tissue, situated between the scleraand the retina , forming the middle coat of the eye. The choroid membrane nourishes the outer portions of the retina and absorbs excess light.
Conductive Keratoplasty (CK): Procedure in which a radio frequency probe, rather than a laser , is used to reshape the cornea . It is approved for low to moderatehyperopia in patients over age 40, however it does not appear to have the precision ofLASIK .
Cones: One of the two types of light-sensitive cells, concentrated in the center of theretina (also see rods ). There are about 6.5 million cones in each eye – 150,000 cones in every square millimeter – responsible for detailed visual acuity and the ability to see in color.
Conjunctiva: Mucous membrane lining the inner surface of the eyelids and covering the front part of the sclera (white part of eye), responsible for keeping the eye moist.
Conjunctivitis: Inflammation or irritation of the conjunctiva . Symptoms can be present in just one eye, or it can affect both eyes and include redness of the eyes or the edges of the eyelids, swelling of the eyelids or itching.
Convergence: Turning of the eyes inwards so that they are both “aimed” towards a nearobject being viewed. Normally works in harmony with divergence which is used for more distant objects.
Cornea: Transparent tissue that forms the front part of the eyeball, covering the irisand pupil. The cornea is the first part of the eye that bends (or refract s) the light and provides most of the focusing power.
Corneal mapping, topography: A tool used to see the refractive problems that might be present in the cornea. Corneal topography is used not only for screening all patients before refractive surgery like LASIK but also for fitting contacts.
Corneal transplant (penetrating keratoplasty): Surgical operation of grafting a replacement cornea onto an eye.
Crystalline lens: Double convex, transparent part of the eye, located behind the irisand in front of the vitreous body. Serves in conjunction with the cornea to refractincoming rays of light onto the retina .
Diabetes mellitus: Chronic metabolic disorder characterized by a lack of insulin secretion and/or increased cellular resistance to insulin, resulting in elevated blood levels of simple sugars (glucose) and including complications involving damage to the eyes, kidneys, nervous system and vascular system
Diabetic retinopathy: Deterioration of retina l blood vessels in diabetic patients, possibly leading to vision loss.
Diopter: Unit of measure of the refractive power of an optical lens (equal to the power of a lens with a focal distance of one meter). A negative diopter value (such as -3D) signifies an eye with myopia and positive diopter value (such as +3D) signifies an eye with hyperopia .
Emmetropia: Twenty-twenty vision.
Endothelium: Cellular tissue that covers the inner surface of the eye within the closed cavity, typically referring to the cornea .
Enhancement: An additional LASIK procedure, used in the refinement of Personal Best Vision.
Extracapsular cataract surgery: Surgery in which the cataract is removed in one piece through a larger incision, which usually requires several stitches.
Extraocular muscles: Six muscles that control eye movement. Five originate from the back of the orbit; the other one originates from the lower rim of the orbit. Four move the eye up, down, left and right, the other two control the twisting motion of the eye when the head tilts. All six muscles work in unison; when they do not function properly, the condition is called strabismus .
Eye chart: Technically called a Snellen chart, a printed visual acuity chart consisting of Snellen optotypes, which are specifically formed letters of the alphabet arranged in rows of decreasing letter size.
Farsighted: Common term for hyperopia .
Femtosecond laser: Used in the IntraLASIK procedure to make a safer and more precise flap than the older mechanical microkeratome technology, it uses a longer wavelength, smaller spot, and shorter duration per pulse than the excimer laser used to reshape the cornea .
Fluorescein angiography: Diagnostic test by which the veins deep inside the eye are examined. Dye is injected into a vein in the arm and circulated by the blood to the back of the eye, allowing for visual examination.
Fovea: Small depression in the retina , the point where vision is most acute.
Giant papillary conjunctivitis: Type of conjunctivitis wherein bumps or ridges form on the inside of eyelids, which make wearing contact lenses uncomfortable; in fact, this condition is often caused by overwearing of certain contact lenses
Gonioscopy: Viewing procedure utilizing a mirror/lens device placed directly upon thecornea that is used to view the drainage area called “the angle” through which aqueous fluid exits the eyeball.
Haptics: The arms of an intraocular lens , which holds it in place once inserted inside the eye.
Haze: Corneal clouding that causes the sensation of looking through smoke or fog.
Holmium laser: A laser which operates in the infrared wavelength, producing a hot beam. It is used in Laser Thermokeratoplasty surgery and more commonly in surgical procedures involving the disintegration of stones and fibrous tissue ablation .
Image: Light reflected into the eye, off objects in front of the eye. This light contains all the information about the objects (such as color, shadow. motion and detail) that are translated to the brain and allow you to “see” (know about the objects).
Intracapsular cataract surgery: Cataract surgery in which both the lens and capsule are completely removed, a rarely used procedure.
Intraocular pressure (IOP): Fluid pressure within the eye created by the continual production and drainage of aqueous fluid in the anterior chamber .
Iridotomy: Treatment for closed-angle glaucoma, one of the many types of glaucoma, usually done with a laser .
Iris: Colored part of the eye. Elastic, pigmented, muscular tissue in front of thecrystalline lens that regulates the amount of light that enters the eye by adjusting the size of the pupil in the center.
Intacs: Surgically implanted plastic half rings that change the shape of the cornea .
Keratectomy: Surgical removal of cornea l tissue.
Keratitis: Inflammation of the cornea
Keratotomy: Surgical incision (cut) of the cornea . .
Keratomileusis: Carving of the cornea to reshape it.
Keratoplasty: Surgical reshaping of the cornea .
LASEK: Laser Epithelial Keratomileusis, a refractive surgery in which the epithelium is cut with a fine blade, called a trephine, and involves displacing the cornea l epithelium as a sheet and then replacing it to (theoretically) act as a natural bandage.
Laser: Device that generates an intense and highly concentrated beam of light. Acronym for: Light Amplification by Simulated Emission of Radiation. (Also see:holmium laser , argon laser , Nd:YAG laser , femtosecond laser , and excimer laser )
Laser Thermokeratoplasty (LTK): Holmium ‘hot’ beam laser, instead of the ‘cool’ beam excimer laser, is used to treat farsighted patients and is very limited in its application; the effects are not long lasting.
Lens: Same as the crystalline lens . Double convex, clear part of the eye, behind theiris and in front of the vitreous humor. Serves to refract the various rays of light so as to form an image on the retina .
Lenticular: Special non- cataract lenses for patients who have cataracts.
LTK (Laser Thermal Keratoplasty): Holmium ‘hot’ beam laser, instead of the ‘cool’ beam excimer laser, is used to treat farsighted patients and is very limited in its application; the effects are not long lasting.
Macula: Yellow spot on the retina , where the photoreceptors are most dense and responsible for the central vision. Has the greatest concentration of cones, responsible for visual acuity and the ability to see in color.
Macular edema: Collection of fluid in and under the macular portion of the retina .
Meridian: Orientation of a particular curve, often used in relation to the cornea .
Microkeratome: Mechanical surgical device that is affixed to the eye by use of a vacuum ring. When secured, a very sharp blade cuts a layer of the cornea at a predetermined depth.
Nearsighted: Common term for myopia .
Neuro-ophthalmology: Subspecialty that treats the nervous and vascular systems that involve the eye.
Normal vision: Occurs when light is focused directly on the retina rather than in front or behind it.
Ocular hypertension: Elevated fluid pressure. The normal pressure is about 10 to 21mmHg, with the majority of people falling between 13 and 19. Over 21 is consideredsuspicious. Over 24 cautiously concerned – warranting immediate investigation. Over 30 is considered urgent and a potential emergency situation.
ONH: Optic nerve, optic nerve head. A bundle of nerve fibers about the diameter of pencil that passes through the back of the eyeball, and connects to the nerve fiber layer of the retina . It can be observed directly with an instrument called an ophthalmoscope.
Ophthalmologist: An ophthalmologist is either a medical doctor (MD) or an osteopathic physician (D.O.) who is qualified and especially trained to diagnose and treat all eye and visual system problems, both medically and surgically, as well as diagnose general diseases of the body.
Optic disc: The head of the optic nerve that is formed by the meeting of all retina l nerve fibers.
Optic nerve: Bundle of nerve fibers that connect the retina with the brain. The optic nerve carries signals of light to the area of the brain called the visual cortex, which assembles the signals into images called vision.
Optometrist: Eye care professional, graduate of optometry school, provides non-surgical visual care. Specifically educated and trained to examine the eyes, and determine visual acuity as well as other vision problems and ocular abnormalities. An optometrist prescribes glasses and contact lenses to improve visual acuity.
Pachymeter: Instrument that measures the distance between the top of the cornea lepithelium and the bottom of the cornea l endothelium used as diagnostic testing device measuring for cornea l thickness.
Pachymetry: Exam for measuring cornea l thickness.
Phacoemulsification cataract surgery: Cataract removal procedure which involves making a tiny incision, about 1/8″ long. A pen-like instrument, inserted through the opening, is used to emulsify and aspirate the clouded lens material, using gentle sound waves. Then an intraocular lens is inserted into place.
Phacofracture cataract surgery: Cataract surgery in which the lens is removed through a small incision by “fracturing” it into several small segments, rarely used today.
Photocoagulation: Focusing of powerful light rays onto tiny spots on the back of the eye, producing heat, which seals retina l tears and cauterizes small blood vessels.
Photo Refractive Keratectomy (PRK): Surgery in which a small area on the cornea lepithelium (surface cells) is gently polished away. The laser then reshapes the cornea l surface in exactly the same way as for LASIK surgery.
Pingecula: Irritation caused degeneration of the conjunctiva resulting in a thickening and yellowing of the normally thin transparent tissue.
Posterior capsule: The thin membrane in the eye that holds the crystalline lens in place.
Posterior Vitreous Detachment (PVD): Separation of the vitreous body from its attachment from the retina l surface due to shrinkage from degenerative or inflammatory conditions or trauma. An age-related condition.
Prescription: Amount of vision correction necessary, written in a form that can be utilized during the manufacture of corrective lenses or to configure a laser machine.
PRK: Acronym for Photo-Refractive Keratectomy, which is a 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 .
Punctum: The hole in the upper and lower eyelids through which tears exit the eye. In patients with dry eyes, temporary or permanent plugs may be inserted to help keep tears in the eye. Tears flow through the punctum to the nose, which is why people often experience a runny nose when crying.
Pupil: Black circular opening in the center of iris through which light passes into thecrystalline lens . It changes size in response to how much light is being received by the eye, larger in dim lighting conditions and smaller in brighter lighting conditions.
Retina: Layer of fine sensory tissue that lines the inside wall of the eye, composed of light sensitive cells known as rods and cones . Acts like the film in a camera to capture images, transforms the images into electrical signals, and sends the signals to the brain by way of the optic nerve.
RK: Abbreviation for ” radial keratotomy “, an outdated procedure once used to correct mild to moderate myopia , whereby making a series of spoke-like incisions around its periphery flattens the cornea .
Rods: One of the two types of light-sensitive cells, located primarily in the side areas of the retina (also see cones). There are about 125 million rods , which are responsible for visual sensitivity to movement, shapes, light and dark (black and white) and the ability to see in dim light.
Routine eye exam: To test the overall condition of the eye and prescribe corrective measures such as glasses, contact lenses or LASIK .
Sclera: White part of the eye. Tough covering that (with the cornea ) forms the external, protective coat of the eye.
Strabismus: Condition occurs when the muscles of the eye do not aligned properly and binocular vision is not present. Patients with a history of strabismus may develop double vision after refractive eye surgery.
Stroma: Middle, thickest layer of tissue in the cornea .
Suspensory ligament of lens: Series of fibers that connect the ciliary body of the eye with the lens, holding it in place; ; also known as zonules.
Topography: A tool used to see the refractive problems that might be present in the cornea. Corneal topography is used not only for screening all patients before refractive surgery like LASIK but also for fitting contacts.
Toric: Lens (eyeglasses, intraocular lens , or contact lens) that is the warped (astigmatic) opposite to that of the eye, thereby canceling out the error.
Trabeculoplasty: A procedure for the treatment of glaucoma, using a laser ( Argon orNd:YAG ). Trabeculoplasty remodels the trabecular meshwork in order to increase drainage of aqueous and lower the intraocular pressure .
Twenty-twenty, 20/20 vision: To have 20/20 vision means that when you stand 20 feet away from the Snellen eye chart you can see what the majority of people can see at that same distance.
UCVA: Uncorrected visual acuity.
Ultrasonography: Recordings of the echoes of ultrasound waves sent into the eye and reflected from the structures inside the eye or orbit. Ultrasonography is used to make measurements and to detect and localize tumors and retina l detachments.
Ultraviolet radiation: Radiant energy with a wavelength just below that of the visible light. UV-c is the shortest wavelength at 200-280 nm and is absorbed by the atmosphere before reaching the surface. UV-b, at 280-315 nm is the burning rays of the sun and damages most living tissue. UV-a, at 315-400 nm is the tanning rays of the sun and is somewhat damaging to certain tissues. UV radiation has been described as a contributing factor to some eye disease processes, which result in ARMD and cataracts and causes exposure keratitis.
Vision therapy: Orthoptics, vision training, eye exercises. Treatment process for the improvement of visual perception and/or coordination of the two eyes, for more efficient and comfortable binocular vision.
Visual acuity: Clearness of vision; the ability to distinguish details and shapes, which depends upon the sharpness of the retina l image.
Visual field: Area or extent of space visible to an eye in a given position of gaze. There is a central visual field – the area directly in front of us, and a peripheral visual field – our “side vision”. The fields of each eye partly overlap. We do not perceive the blind spots from each eye because the area that is missing in one eye is present in the other.
VISX CustomVue Procedure: WaveScan-driven laser vision correction with the potential to produce better vision than is possible with glasses or contact lenses, and enable surgeons to measure and correct unique imperfections in each individual’s vision.
Wavefront: Wavefront technology produces a detailed map of the eye. The information is transferred to the laser via computer software.
YAG laser surgery: Properly called Nd:Yag laser capsulotomy, a procedure using a Nd:YAG (neodymium-yttrium-aluminum-garnet) laser, used primarily to treat secondary cataract s (capsular haze) that occur subsequent to the primary cataractprocedure, or to relieve increased pressure within the eye from acute angle-closure glaucoma via a peripheral iridotomy. It can also be used to treat open angle glaucoma in a procedure called selective laser trabeculoplasty.