Ophthalmology Glossary of Terms


A Back to Top

Abrade: To roughen by rubbing or scraping, thus removing small pieces of surface tissue.
Accommodation: The eye’s ability to switch focus from near objects to far objects. It’s done by tiny muscles attached to the eye’s lens, which pull on the lens to change its convexity. As we age, those muscles become weaker and the lens becomes stiffer, a condition known as presbyopia, where reading glasses become necessary to see close-up objects.
Acuity: Clarity or sharpness of vision, commonly expressed as 20/20 vision in relation to the Snellen acuity chart. This is the eye chart seen at every eye doctor’s office, with the big E at the top.
Acute: Occurring suddenly.
Age-Related Macular Degeneration (ARMD): Deterioration, as people age, of the macula lutea (also called the yellow spot), which is a small area on the retina which gives maximum vision. If left untreated, it results in blindness.
AK: Astigmatic Keratotomy, an ophthalmological procedure for correcting astigmatism.
Algorithm: A mathematical formula such as is used when preparing for a LASIK, PRK, LASEK or Epi-LASIK surgery, to set the laser’s ablation area on that particular individual’s eyes.
ALK: Automated Lamellar Keratectomy, a procedure to correct opacities on the corneal surface.
Allegretto: A manufacturer of medical equipment.
Allergan: A company that makes ophthalmic equipment and drugs.
Ametropia: A generic name for eye conditions characterized by impaired refraction, e.g. myopia, hyperopia and astigmatism.
Amsler grid: A test used to detect defects or distortions in the central visual field. It consists of a square subdivided into many hundreds of small squares by horizontal and vertical lines, with a small dot in the center.
Angle: Drainage area of the eye formed between the cornea and the iris, named for its angular shape, which is why you see the word “angle” in the different glaucoma names.
Anterior: An anatomical term meaning the front part of a structure as opposed to the posterior, the back part.
Anterior Basement Membrane Dystrophy: The most common corneal dystrophy. An eye condition where the membrane that lies beneath the epithelial cells (surface cells) of the cornea is uneven and traps cells below it which should normally rise above it. It impairs vision, is usually hereditary, and fluctuates in severity over the person’s lifetime. It’s also called Map-Dot-Fingerprint Dystrophy (a name based on how it looks microscopically), and Epithelial Basement Membrane Dystrophy.
Antimetropia: A condition where one eye is nearsighted and the other one farsighted.
Aphakia: Absence of the crystalline lens in the eye.
Asthenopia: Eyestrain.
Astigmatism: An eye condition where the cornea is oval-shaped rather than round. This oval shape has two curves: the steeper one and the flatter one. Each curve refracts light at a different angle, sending it to focus on the retina in two different places, and creating distorted vision. It can be mild, with just blurriness, or more severe, with ghosting and severe blurring. In a glasses prescription, the second number expresses the degree of astigmatism you have, and the next number is the number of degrees in the angle of refraction. For example, a prescription of –4.00 – 2.00×34o states that you have 2 diopters of astigmatism at an angle of 34 degrees。
Automated Lamellar Keratoplasy (ALK): A refractive eye surgery that treats myopia. The surgeon uses a microkeratome to cut a very thin shaving or flap from the corneal surface. Then a tiny piece even thinner is removed from the underlying tissue, to flatten the cornea a little, and the flap is replaced. It heals up without any need of stitches.
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.

B Back to Top

B scan: An ultrasonic procedure that checks for abnormalities in the eye, and locates foreign bodies within it.
Basement Membrane: A microscopically thin layer of tissue below the epithelial cells (surface cells) of the cornea, connecting those cells to the stroma, which is the middle layer of cells in the cornea.
Bifocals: Glasses designed to correct for both near vision and far vision. A small area at the lower edge of the lens is set for reading or other close-up activities and the rest of the lens gives clearer distance vision according to your prescription. Used by people with presbyopia. See also trifocals.
Binocular: An adjective meaning with both eyes, e.g., binocular vision.
Black Box Laser: A laser (usually imported to the U.S.) used by some eye surgeons that has been altered so it can do LASIK and other laser eye surgeries, but this alteration is not approved by the FDA. The safety consequences of using a black box laser have not been studied and are completely unknown.
Blepharitis: Chronic inflammation of the eyelids. It can be caused by an allergic reaction to some product, excess oil excreted by eyelid glands, bacterial infection, or poor facial hygiene.
Blind Spot: (a) The place on the retina where the optic nerve enters the eye. No visual cells are on the retina here, so no vision is possible at this place. In this sense, it’s a normal thing. (b) Also refers to any gap in a person’s visual field that corresponds to any area on the retina where visual cells are missing and in this sense, it’s associated with eye disease.
Board Certified: This is the phrase used for approval by the American Board of Ophthalmology (ABO), a non-profit and independent organization that was founded in 1916 to certify ophthalmologists.
Broadbeam: The term used for applying the excimer laser to the entire treatment area at one time. It’s the typical way laser treatment is done for myopia, hyperopia and astigmatism. See also Flying Spot and Variable Spot.
Buttonhole Flap: A LASIK problem where the microkeratome cuts through the top surface of the cornea while creating the corneal flap, while lifting it, or while folding it back. It can be caused by loss of the suction which holds the microkeratome against the cornea, or inadequate suction, or by poor matching of microkeratome to patient. If possible, the flap is replaced, and no further surgery is attempted for several months, after it has healed. Sometimes it can cause scarring which impairs vision, but usually there are no permanent ill effects.

C Back to Top

Cataract: An opaque or cloudy area that forms in the eye’s lens, impeding vision. They tend to occur with aging, but can also be caused by trauma. Cataracts are treated by the lens being removed and an artificial lens implanted. See intraocular lens.
Central Ablation Zone: The ablation zone is the area of the eye treated by the laser in LASIK surgery. Around it is the transition zone, where the treated area gradually merges with the original corneal surface that lies outside the ablation zone.
Central Island: An area of the laser-treated part of the cornea which is erroneously not treated, so that its level remains microscopically higher than the surrounding treated surface. The term island describes its appearance. It causes diplopia (double vision).
Choroid: Part of the uvea, the eye’s middle membrane between the retina and the sclera. It has many blood vessels with smaller ones next to the retina and larger ones next to the sclera. It also has large pigment cells.
Chronic: Of long duration, going on for some time.
Closed angle glaucoma: Glaucoma conditions occurring suddenly (acute).
Clear Lens Extraction (CLE): Procedure in which the eye’s natural clear crystalline lens is removed and replaced with an intraocular lens implant , using the same technique as cataract surgery.
Color Blindness: Abnormal color vision where the person confuses red and green. It usually occurs in males as the relevant gene is located on the X chromosome.
Co-management: Collaboration between two or more doctors in caring for a patient. For refractive surgery, usually an optometrist co-manages with an ophthalmologist. The optometrist provides the pre-operative testing and post-operative care, while the ophthalmologist does the surgery itself.
Comprehensive eye exam: Evaluation of the complete visual system.
Coma: A higher order aberration which makes points of light look like comets with blurry tail-like smudges. It can be diagnosed and treated with wavefront-guided LASIK procedures.
Complex Wavefront Retreatment: An off-label use of the excimer laser to do corrective secondary surgery after the original wavefront-guided surgery has left the patient with higher-order aberrations.
Cones: A type of retinal cell which is light-sensitive and gives us sharp central vision in bright light. They detect color, and there are three kinds: one absorbs red wavelengths, one absorbs green wavelengths and the third absorbs blue wavelengths. Cones are mostly clustered in the central area of the retina.
Concave Lens: The type of lens used to correct nearsightedness (myopia). Concavity is the hollow type of curve that recedes in the center and raises up at the edges, opposite to convex.
Contact Lens Assisted Pharmacologically Induced Kerato Steepening: A way to undo overcorrection in laser eye surgery (LASIK, PRK and RK). A tightly-fitting contact lens is placed on the eye and anti-inflammatory eyedrops are used. The goal is to make the cornea more steep, after it’s been made too flat.
Contact Lens Disinfectant: A solution for removing bacteria and micro-organisms from contact lenses.
Contact Lens, Daily Wear: Contact lenses designed to be worn only during the daytime.
Contact Lens, Disposable: Contact lenses designed to be worn once and then thrown out, as opposed to the kind that’s removed, cleaned, and reinserted. Depending on the eye doctor’s prescription, disposable contact lenses can be worn for one day, or for up to a week.
Contact Lens, Extended Wear: Contact lenses designed to be worn continuously for up to a week, not being removed for sleep.
Contact Lens, Therapeutic: Special contact lenses designed to help heal the eye and protect it while it heals. They’re often used along with eyedrops specially-prescribed to promote healing.
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.
Convex Lens: Lenses with the opposite curvature to concave lenses. They bulge outwards like a ball and are used to correct hyperopia and presbyopia.
Corneal Abrasion: A scrape or scratch on the cornea, the front surface of the eye.
Corneal curvature: Shape of the front of the eye.
Corneal Ectasia: A complication of LASIK similar to the inherited condition of keratoconus. It can happen when the eye was over-treated by a LASIK procedure, so that not enough thickness is left in the cornea to contain the eye’s internal pressure. That pressure pushes against the cornea and causes it to bulge outward. Vision then becomes progressively worse.
Corneal Flap: A small circular piece of the cornea’s surface layer (epithelium) which is cut, all but one section like a hinge, and folded back before the laser treats the stroma. After treatment, it’s folded back into position and heals by itself in a few days. Very occasionally there are complications with this flap. For example, it may have been sized wrongly, or cut too deeply, it might be completely cut instead of retaining a hinge, or it might heal in the wrong position, with a slight wrinkle or with swelling. Many of these complications can be dealt with successfully.
Corneal Haze: An after-effect of Excimer laser surgery, where the cornea develops opaque white cells which cloud the vision to some extent. It can cause glare from bright lights and a vague fogginess of vision. It usually clears up after 6 or 8 months. If it persists, there’s an enhancement procedure which can reduce it. As vision correction techniques improve there’s less incidence of corneal haze.
Corneal Refractive Therapy: A reshaping of the eye with contact lenses, also called Orthokeratology. These lenses are rigid and worn while you sleep, so they gently persuade the eye to change its shape by the time you wake in the morning. The effect lasts only a day or two, so you need to wear these lenses every night. It was approved by the FDA in June, 2002 and is a non-surgical way of temporarily creating the effect created permanently by LASIK surgery.
Corneal Topographical Map: A map of the cornea that shows its surface profile.
Corneal Topographer: A specialized camera-computer system which photographs and prints out a map of the surface details of a cornea. This is done before any LASIK procedure.
Corneal transplant (penetrating keratoplasty): Surgery to replace the cornea, the clear front area of the eye. Corneal tissue comes from a donor and since the cornea has a small blood supply, there is little risk of rejection, and the new cornea can function very well for years. A corneal transplant can be done to treat Keratoconus, Fuch’s Dystrophy, or damage from a severe infection or injury. It’s a painless outpatient procedure.
CrystalensT: An accommodative intraocular lens used to treat cataracts and presbyopia. Manufactured by Bausch & Lomb and approved by the FDA in November, 2003 for replacing the eye’s natural lens.
Crystalline lens: The eye’s natural lens, which is behind the iris and in a healthy eye is completely clear. Light passes through it and is refracted by the lens to focus on the retina. Tiny muscles attached to the lens change its convexity according to where the eye is focused. As we age, it can start to become cloudy (cataracts), impairing our vision.

D Back to Top

Decentration: A complication of eye surgery. When centration is perfect, the corneal ablation, or the position of the intraocular lens being implanted, is in the center of the eye, lined up with the pupil. Then vision is perfectly centered through the ablated area and pupil, so that we see clearly and fully, like looking through the center of your glasses. When decentration happens, the ablation has been done off-center, or the lens’ position is shifted, so that vision is partially corrected and partially as it was originally.
Degenerative Myopia: Nearsightedness thought to be hereditary, which may start at birth, or in later childhood. It’s a more severe form of myopia and can lead to blindness. It’s associated with to cataract formation and with retinal changes and can lead to retinal detachment.
Diabetes type I (IDDM): Insulin-dependent diabetes, also known as juvenile diabetes because it’s often diagnosed in young people. The pancreas, which normally would produce insulin, is unable to do so, so insulin must be injected so the patient can convert sugars and starch into energy. A person with Diabetes, Type 1 or 2, is susceptible to vision problems because the tiny blood vessels in the eyes weaken and start to leak, damaging the retina. See Diabetic Retinopathy.
Diabetes type II (NIDDM): The more common of the two types of Diabetes, where the pancreas can produce insulin, but not enough. Insulin may or may not have to be injected for the person to convert sugars into energy. Sometimes Type 2 can be well-managed by sticking to the right diet and exercise routines.
Diabetic retinopathy: Damage done to the small blood vessels that feed the retina. In the early stage it’s known as background diabetic retinopathy. The small arteries in the retina weaken and leak, which often causes swelling and impaired vision.
The later stage is called proliferative diabetic retinopathy. Since the arteries are not functioning well to bring oxygen to the eye’s cells, retinal cells become ischemic (lacking in oxygen). The eye develops new blood vessels (a response known as neovascularization) but these are weak and also start leaking, so the problem becomes worse.
Eventually, as the body continues to grow extra blood vessels, which continue to leak, scars can form, and the retina can detach from its membrane at the back of the eye, causing blindness.
Diopter: The unit of measurement for a lens. Positive diopter numbers indicate the lens is convex (curving outwards) and negative numbers indicate it’s concave. A one-diopter lens will bend straight light rays to focus them one meter away from itself. A two-diopter lens will bend them to focus only a half-meter from itself. A lens with any minus number doesn’t focus the light rays, but scatters them.
Divergence: Turning of the eyes outwards so that they are both “aimed” towards the object being viewed. Normally works in harmony with convergence.
Dominant Eye: The eye that looks directly at an object. The non-dominant eye looks at it from a slight angle, and this combination creates depth perception.
Double vision: Same as diplopia.
Dry eye Syndrome: Insufficient moisture in the eye, which gives a feeling of grittiness, burning, stinging, or uncomfortable dryness, and extra sensitivity to light. It can be a symptom or complication of another condition, or caused by certain medications. It is also a common temporary result of a LASIK procedure. It can be treated with moisturizing eyedrops, eyedrops which stimulate more tear production, or punctal plugs which block the drainage into the nasal passages and sinuses. passages and sinuses. passages and sinuses.
DSAEK: DSAEK (Descemet’s Stripping Automated Endothelial Keratoplasty) is a new procedure devised in 2007 for improving a corneal transplant. Descemet’s Membrane (named after French physician Jean Descemet (1732-1810), is the basement layer, the innermost of the cornea’s five layers. DSAEK transplants only this very thin layer rather than the entire cornea. The replacement layer from a donor stays in place without the need for any sutures. Recovery from DSAEK is one to three months, as compared to the one to two years’ recovery required by a full corneal transplant.
Dystrophy: Weakening or wasting of body tissue, such as happens in Epithelial Dystrophies and Stromal Dystrophies, where abnormalities appear in different corneal membranes, causing loss of function and often impairing vision.

E Back to Top

Emmetropia: Twenty-twenty vision.
Endothelium: A lining of flat cells inside the cornea, facing on to the anterior chamber.
Epikeratome: A surgical tool similar to a microkeratome, used to make the corneal flap in an Epi-LASIK procedure. It has a blunt separator where the microkeratome, used in LASIK procedures, has a very thin and sharp blade. It’s another way of making the corneal flap and does not involve the use of alcohol, as LASEK procedures do. Each way of making the corneal flap has its advantages and disadvantages and consultation with an experienced eye surgeon will determine which would be best for you.
Epi-LASIK: A variation on the basic LASIK treatment, where instead of using a microkeratome to cut the corneal flap before applying the laser, an epikeratome is used. This instrument gently separates the epithelial cells. Epi-LASIK is done for people whose corneas are too flat for traditional LASIK.
Epithelial Dystrophies: A group of inherited dystrophies where the surface layer of the cornea atrophies and vision is impaired. See Anterior Basement Membrane Dystrophy, Reis-Buckler’s Dystrophy, and Meesmann’s Dystrophy.
Esotropia: Inward turning of the eyes; crossed eyes. Usually one eye looks straight ahead and the other turns inward.

F Back to Top

Farsightedness: Common term for hyperopia .
Flap: Part of the cornea consisting of epithelium , Bowman’s membrane and some stroma , cut with a remaining hinge and lifted up as part of the LASIK procedure.
Flying Spot: A method of applying the excimer laser light used in refractive surgery. A flying spot laser is used, which has a 1mm: 2mm diameter light beam. The computer that controls the laser is programmed to send pulses to changing spots on the cornea, with no spots overlapping. Part of the ophthalmic laser system is an eye tracker, which responds to all eye movement during surgery. So even if the eye moves while it’s being treated, the entire targeted area will be treated, because the treatment plan has determined where the laser should shine, in the series of flying spots that will cover it entirely, and the whole system moves to correspond with any eye movements during surgery.
Focusing power of the eye: The combined action of the cornea and the lens to refract light on to the retina.
Fuch’s Dystrophy: A progressive, inherited eye disease (dystrophy) in which the cornea loses cells from the endothelium which normally remove fluids and impurities from the eye. Without those cells, the eye retains too much fluid and begins to swell. By changing the cornea’s curvature, this makes vision blurry, especially first thing in the morning, since while the eyes are closed in sleep, no moisture can evaporate from them. It causes other symptoms, e.g. blisters, light sensitivity, pain, and decreased depth perception. There is no cure, but there are some ways to minimize symptoms. A corneal transplant eventually becomes necessary. Also called Endothelial Dystrophy.

G Back to Top

Ghosting: A name for double vision. The eye sees objects in duplicate, with the second image fainter than the main one.
Glare: Scatter from bright light that decreases vision.
Glaucoma: An eye disease where pressure builds up inside the eye. If it isn’t diagnosed and treated, it can damage the optic nerve, reducing the field of vision gradually, until blindness results. It’s treated with special eye drops which lower the pressure.
Gonioscopy: Viewing procedure utilizing a mirror/lens device placed directly upon the cornea that is used to view the drainage area called “the angle” through which aqueous fluid exits the eyeball.
Granular Dystrophy: A hereditary eye condition where pale gray granules appear in the stromal layer of the cornea, like little crumbs. It’s usually detected by the time a person is about 20. By age 40 or so, vision will be increasingly impaired as those granules, or lesions, expand, increase in number, coalesce, and penetrate more deeply into the stroma. It can be treated in earlier stages with an excimer laser, or in other ways that remove the granules, and later on by a corneal transplant.

H Back to Top

Halos: A visual condition where a light source appears with a blurry circle of light around it, rather than having visible edges. It can be a complication of refractive surgery, and can also occur naturally. It makes night vision difficult.
Haze: Clouding of the cornea. It can be caused by inflammation, too much moisture, scar tissue, or some kind of foreign substance as from a medication.
Higher Order Aberration: Irregularities of the eye that are not refractive.
Hypoxia: Deficiency of oxygen supply to a tissue.

I Back to Top

ICL (Implanted Collamer Lens): The name used for the STAAR Visian ICL™, created by the STAAR Surgical Company and approved by the FDA in 2005 for treating myopia. It is a refractive lens for use in a phakic eye (an eye with its natural lens intact) and is positioned in front of or behind the natural lens to modify the lens’ refractive power.
iLasik: The name for vision correction surgery which combines the Intralase technology manufactured by Advanced Medical Optics, Inc. (AMO) and the VISX Excimer technology originally marketed by the company VISX which was acquired by AMO in 2006. It is an Intralase procedure using the VISX hardware.
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).
In Situ: Term meaning “in place”.
IntraLASIK: A variation on a LASIK procedure. See IntraLase.

K Back to Top

Keratectomy: Surgical removal of cornea l tissue.
Keratitis: Inflammation of the cornea caused by bacteria or a virus. Can leave scarring and cause loss of vision.
Keratotomy: Surgical incision (cut) of the cornea . .
Keratoplasty: See corneal transplant.
Keratomileusis: Carving of the cornea to reshape it.
Keratoplasty: Surgical reshaping of the cornea .

L Back to Top

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.
Lattice Dystrophy: A hereditary corneal condition where abnormal protein fibers appear on the stroma.
Limbus: Thin area that connects the cornea and the sclera .
Low vision: Condition occurring when ordinary eyeglasses or contact lenses are unable to bring a patient’s sight up to normal sharpness.

M Back to Top

Macular Degeneration: A deterioration of specialized cells in the macula of the retina which normally detect light and color to give us sharp central vision.
Macular Dystrophy: A hereditary type of macular degeneration.
Macular edema: Pooling of fluid in and around the macular area of the retina, which causes swelling and impairs vision.
Manifest Refraction: The eye examination which determines a person’s degree of refractive error.
Meesmann’s Dystrophy: A rare hereditary eye condition where tiny cysts appear on the corneal surface which can rupture.
Micron: A measurement of length equal to one-millionth of a meter.
Miosis: Pupillary constriction.
Monocular: An adjective for vision out of one eye. Also the name of a type of telescope.
Mydriasis: Pupillary dilation.

N Back to Top

Nearsighted: Common term for myopia. The inability to see distant objects as clearly as near objects.

O Back to Top

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 considered suspicious. Over 24 cautiously concerned – warranting immediate investigation. Over 30 is considered urgent and a potential emergency situation.
OD: Abbreviation standing for “oculus dextrum” meaning: right eye.
ONH: Optic nerve, optic nerve head. A bundle of nerve fibers about the diameter of pencil that pass 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.
Optician: Experts who designs, verifies and dispenses lenses, frames and other fabricated optical devices upon the prescription of an ophthalmologist or an optometrist.
OS: Abbreviation standing for “oculus sinistrum” meaning: left eye
Overcorrection: Occurence in refractive surgery where the achieved amount of correction is more than desired; in LASIK , typically due to a patent’s over-response to the laser ablation.

P Back to Top

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.
Phoropter: A common device found in most eye doctor’s offices, with mulitple lenses, used to measure refractive errors. A phoropter calculates the prescription required for corrective lenses.
Photophobia: Sensitivity to light.
Pink eye: Type of conjunctivitis, commonly seen in children.
Posterior chamber: The back section of the eye’s interior.
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. It is an age-related condition.
Prelex: Surgical procedure that attempts to correct presbyopia.

R Back to Top

Refract: To bend aside, as in “the crystalline lens refract s the light as it passes through”, or to measure the degree the eyes or lenses bend light, as in “the doctor refract s a patient’s eyes”.
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 .

S Back to Top

Schirmer test: Test for dry eyes, which use a thin strip of filter paper placed at the edge of the eye.
Single vision: Lenses with only one focal length.
Snellen lines: Snellen optotypes arranged in horizontal rows called “lines”.
Sphere: Focusing power of the corrective lens.
Stereoscopic vision: Ability to see in three-dimension.
Stereopsis: Ability to perceive three-dimensional depth.
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.

T Back to Top

Trabecular meshwork: Drainage channels located inside the eye.

U Back to Top

UCVA: Uncorrected visual acuity.
Uveitis: Inflammation of any portion of the uveal tract.
Undercorrection: Occurence in refractive surgery where the achieved amount of correction is less than desired; in LASIK , typically due to a patient under-responding to the laser treatment.

V Back to Top

Vascular: Having to do with transporting blood.
Visual cortex: That part of the brain responsible for vision.
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.

W Back to Top


Y Back to Top
