Choose a Topic
A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - Z
A
Accommodation
The eye's ability to adjust its focus from distant to near objects. This process is achieved by the lens changing its shape.Go to Top
Acuity
The clearness of eyesight; the keenness of the visual powers. AKA: Visual Acuity.Go to Top
Age-Related Macular Degeneration (ARMD, AMD or ARM)
A major cause of central vision loss which, in about 70% of the cases, is associated with aging and the breakdown of the retinal structures at the macula.Go to Top
Albinism
Congenital deficiency or absence of pigment (color) in the skin, hair, choroid, retina and iris.Go to Top
Amaurosis
Blindness.Go to Top
Amblyopia
Sometimes referred to as lazy eye, a condition of diminished visual acuity in the absence of any detectable anatomic or physiologic cause.Go to Top
American National Standards Institute (ANSI) Z87.1
The American National Standards Institute's Practice for Occupational and Educational Eye and Face Protection; eyewear that meets this standard is considered safer than eyewear that does not.Go to Top
Ametropia
Defective vision that is correctable by eyeglasses, contact lenses, or refractive surgery.Go to Top
Aniseikonia
A condition in which the image sizes in each eye are different, leading to difficulties in achieving single vision. Symptoms of aniseikonia are headaches and dizziness.Go to Top
Anisocoria
Different-sized pupils in each eye. This may be physiological (naturally occurring) or may be a sign of a more serious disorder.Go to Top
Anisometropia
Greek meaning "not the same correction," anisometropia is when there is a significant difference in correction between the two eyes. This may cause eye strain and double vision (diplopia).Go to Top
Anterior Chamber
The space in front of the iris and behind the cornea.Go to Top
Antimetropia
One eye nearsighted; the other farsighted.Go to Top
Anti-Reflective Coating
Anti-reflective treatments reduce glare and enhance your appearance by removing distracting reflections. An anti-reflecive treatment helps reduce strain often caused by lights at night, fluorescent lighting, and computer screens.Go to Top
Aphakic
Condition of the eye with crystalline lens removed without anything being put in its place. Modern cataract surgery removes the lens, but an intraocular lens is often put in its place.Go to Top
Aqueous Humor
Also known as aqueous fluid. A clear, watery fluid that flows around and nourishes the lens, retina, and the cornea.Go to Top
Arteriosclerosis
A chronic disease of the arteries characterized by the thickening or hardening of the arterial walls impairing blood circulation.Go to Top
Asthenopia
A group of symptoms generally referred to as "eye-strain." Included are: headaches, tearing, "tired eyes," itching, burning and blurred vision.Go to Top
Astigmatism
A condition that occurs when the front surface of the eye (the cornea) is slightly irregular in shape. This irregular shape prevents light from focusing properly on the back of the eye (the retina). As a result, vision may be blurred at all distances. Astigmatism can be corrected with glasses, contact lenses, or refrative surgery.Go to Top
B
Bifocal Lens
Lens with two focal lengths, one for distance and one for near. Usually the distance correction is on top and the correction for near is on the bottom.Go to Top
Blended Lens
While traditional multifocal lenses have a line in the middle of the lens, blended lenses (progressive lenses) are line-free. The power gradually changes from distance correction to intermediate vision (at arm's length), to near vision (at reading distance), moving invisibly from the top to the bottom of the lens.Go to Top
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.Go to Top
C
Cataract
A cataract is a clouding of part or all of the lens inside the eye, resulting in blurred or distorted vision.Go to Top
Cataract Lens
Lens used following cataract removal. Cataract lenses were once widely used for post-cataract patients; however, IOL (interocular) lenses are now the most commonly used replacement for the removal of crystalline lens, eliminating the necessity for cataract lenses.Go to Top
Choroid
The layer in the eye filled with blood vessels that nourishes the retina.Go to Top
Chromatic
Of or pertaining to color.Go to Top
Ciliary Muscle
The eye's focusing muscle that allows the crystalline lens to perform its function of accommodation.Go to Top
Clear Lens Extraction (CLE)
A procedure where the lens is removed to correct myopia.Go to Top
Coloboma
A defect of the iris or retina caused by a failure of the eyeball to fuse properly during fetal development. These are developmental anomalies and do not worsen as the child grows older.Go to Top
Color Blindness
More appropriately known as color deficiency, it refers to the inability to recognize certain colors. The most common deficiency is red-green deficiency. Blue-yellow color deficiency also exists, but is more rare. True color blindness is quite rare and is usually accompanied by poor visual acuity and extreme light sensitivity.Go to Top
Computer Vision Syndrome (CVS)
The variety of eye and vision-related problems associated with prolonged computer use. CVS is characterized by eyestrain, blurred vision, headaches and dry or irritated eyes.Go to Top
Conjunctiva
The thin, moist tissue that lines the inner surfaces of the eyelids and the outer surface of the sclera.Go to Top
Conjunctivitis
Inflammation of the conjunctiva, often referred to as "pink eye." There may be several causes of conjunctivitis, including bacterial or viral infection, allergies, or other etiology.Go to Top
Contact Lens Drops
Eye drops for contact lens wearers; regular eye drops can discolor contact lenses.Go to Top
Contrast Sensitivity
The ability to perceive differences between an object and its background.Go to Top
Convergence
Simultaneous turning in of both eyes to keep objects in sight as they approach the eyes.Go to Top
Cornea
Serving to transmit light to the eye, the cornea is a transparent tissue that covers the front surface of the eye.Go to Top
Corneal Abrasion
A cut or scratch on the cornea.Go to Top
Corneal Implants
Devices (such as rings or contacts) placed in the cornea, usually to correct vision.Go to Top
Corneal Refractive Therapy (CRT)
A process of reshaping the cornea using specially designed gas permeable contact lenses. The patient wears the lenses through the night to shape the cornea, then goes throughout the day without the need for a prescription.Go to Top
Corneal Ring
A type of vision correction surgery where a doctor inserts tiny plastic rings into the cornea, reshaping it to better focus light onto the retina to improve vision. The rings can be adjusted and even removed if desired.Go to Top
Corneal Topography
Mapping or examination of the cornea. The information gathered is useful to evaluate and correct many eye conditions.Go to Top
Corneal Ulcer
A wound in the outer layer of the cornea caused by injury, excessive dryness, or infection.Go to Top
Crystalline Lens
The crystalline lens is located directly behind the iris. It helps focus light on the retina as your focus changes from distance to near.Go to Top
D
Dacryostenosis
A blocked tear duct, which is characterized by a lot of tearing.Go to Top
Daily Wear Contact Lens
Soft contact lenses worn every day for six months up to a couple of years, requiring daily cleaning and disinfecting, as well as a periodic enzymatic soak (usually once a week).Go to Top
Depth Perception
The ability to judge the distance and/or spatial relationship of objects of varying distances.Go to Top
Diabetes
A chronic, metabolic disorder where a lack of insulin secretion and /or increased cellular resistance to insulin results in elevated blood levels of glucose. Visual complications due to diabetes can include the early formation of cataracts, diabetic retinopathy, fluctuating vision, and changes in prescription. Other complications may include damage to the kidneys, liver, nervous system and vascular system.Go to Top
Diabetic Retinopathy
A complication of diabetes that is triggered by damage to the blood vessels of the eye. Early diabetic retinopathy may not be noticable by the patient, but if left untreated may cause permanent vision loss. People with diabetes should have an annual dilated eye examination.Go to Top
Dilate
A process by which the pupil is temporarily enlarged with special eye drops. This allows an eye doctor to see more of the retina and look for signs of diabetic retinopathy and other eye diseases or health concerns. After the exam, close-up vision may remain blurred for several hours and you may be more sensitive to light. A dilated exam is the standard of care.Go to Top
Diopter
A diopter is a unit of measure for expressing the power of a lens or lens system. A one diopter lens has a focal distance of one meter. A two diopter lens has a focal distance of 50 centimeters.Go to Top
Diplopia
Double vision. It may be caused by a number of conditions including: eye misalignment, dry eyes, astigmatism, cataracts, neurological disorder, stroke, or other cause.Go to Top
Disposable Contact Lens
Contact lenses that are thrown away after a short period of time. Usage of disposable contact lenses ranges from one day to two weeks, while frequent replacement lenses are discarded monthly or quarterly.Go to Top
Divergence
Simultaneous turning out of both eyes to keep sight of an object as it moves farther from the eyes.Go to Top
Double Bifocal Lens
An occupational lens with a bifocal on the bottom and the top of the lens.Go to Top
E
Edge Coating
Lens edges can be painted or color-treated to disguise thick edges of lenses or to coordinate with frame color for cosmetic reasons.Go to Top
Edge Polish
Both glass and plastic lens edges can be polished to a high luster resulting in clear and shiny lens edges. This option is often chosen with rimless frames to disguise the edges of the lenses, especially if they are thicker.Go to Top
Endothelium
The cornea's inner layer of cells.Go to Top
Enzymatic Cleaner
Used for contact lenses, a cleaner that removes protein deposits and other debris. It's recommended for use either daily, weekly, or monthly. Some enzymatic cleaners are a small tablet dropped into a solution along with the lens; others come in liquid form.Go to Top
Epithelium
The cornea's outer layer of cells.Go to Top
Esotropia
A misalignment of the eyes where one eye is turned inward with respect to the intended focus point.Go to Top
Exotropia
A misalignment of the eyes where one eye is turned outward with respect to the intended focus point.Go to Top
Executive Lens
Bifocal or trifocal where the near portion(s) of the lens extends across the full width of the lens. Executive lenses offer the advantage of wide field of vision in reading area.Go to Top
Extended Wear Contact Lens
Contact lenses that are worn without removal for up to thirty days.Go to Top
Eye Care Doctor
Optometrists (O.D.s) and ophthalmologists.Go to Top
F
Faceted Lens
Polished, beveled edge lens is put in a rimless frame.Go to Top
Farsightedness
Also known as hyperopia. It is the result of an eyeball that focuses light behind the retina. This may be due to the cornea being too flat or the eye being too short. The exact cause is not known, although farsightedness may be inherited.Go to Top
Floaters
Cells and fragments of debris in the eye that pass across your field of vision. The sudden appearance of floaters may be a sign of a retinal tear or retinal detachment.Go to Top
Focal Length
Distance from the optical center of the back surface of the eye to the principal focus of the lens.Go to Top
Focus
The point at which light rays through a lens form an image.Go to Top
Fovea
A specialized portion of the retina that contains only cones (not rods), and that provides acute eyesight.Go to Top
Frequent Replacement Contact Lens
Any contact lens that is thrown away after a moderately short period of time, anywhere from one day to two weeks (disposables) to monthly or quarterly (frequent replacement).Go to Top
Fundus
The interior lining of the eyeball, including the retina, optic disc, and macula. This portion of the inner eye can be seen during an eye exam by looking through the pupil.Go to Top
G
Gas Permeable Contact Lens (RGP)
Similar in appearance to a hard contact lens, an RGP is a healthier modality due to the increased ability of the lens material to transmit oxygen to the cornea.Go to Top
Ghost Image
Internal reflections from the lens surfaces often referred to when describing the benefits of an anti-reflective coating. Ghost images are mostly experienced at night, but may also be seen under fluorescent lights and when viewing computer screens.Go to Top
Glass Lens
The most scratch-resistant lens material. Heavier than plastic lenses, glass comes in a wide selection of lens styles and can be ordered with absorptive and photochromic tints.Go to Top
Glaucoma
An eye disease in which the passages that allow fluid in the eye to drain become clogged or blocked, or there is too much fluid produced inside of the eye. Increased pressure inside the eye then damages the optic nerve and causes vision loss.Go to Top
Gonioscopy
Use of a special lens to look at the eye's aqueous drainage area. This can be thought of as looking at the drain of the eye to see if it's plugged up.Go to Top
Gradient Tinting
Usually applied for cosmetic purposes, gradient tinting is darker at the top of the lens than in the middle and lightest at the bottom.Go to Top
Graves' Ophthalmopathy
Thyroid-related, autoimmune eye disorder usually associated with Graves' disease; symptoms include eyelid retraction, bulging eyes, light sensitivity, discomfort, double vision and vision loss.Go to Top
Gross Visual Fields
A brief 5 to10 minute test in which the doctor examines your peripheral (side) vision. The test can be conducted using specialized equipment or simply by having you follow a focal point.Go to Top
H
Hard Contact Lens
Compared with soft and gas permeable lenses, hard contact lenses are less healthy to wear long-term, since the material doesn't allow oxygen to reach the surface of the eye.Go to Top
High Blood Pressure (Hypertension)
Abnormally high arterial blood pressure.Go to Top
High Index Lens
A thinner and lighter lens in either glass or plastic, chosen for lightweight comfort and attractiveness.Go to Top
Hyperopia
Also know as farsightedness, the inability to see objects up close. It is the result of an eyeball that is too short or whose outside surface (the cornea) is too flat. The exact cause is not known, although farsightedness may be inherited.Go to Top
Hypertropia
A turning upward of one eye with respect to the other.Go to Top
Hypotropia
A turning downward of one eye with respect to the other.Go to Top
I
Implantable Contact Lens (ICL)
A contact lens that is surgically inserted into the anterior chamber and attached to the iris. This may be utilized as an alternative to LASIK or PRK.Go to Top
Intermediate Zone
Refers to the middle zone of sight. Considered to be an arm's length, the top trifocal segment in a multifocal lens corrects vision for this distance.Go to Top
Intraocular Pressure (IOP)
Pressure inside the eye.Go to Top
Interpupillary Distance
Commonly referred to as PD, the distance between your pupils.Go to Top
Intraocular Lens (IOL)
A lens implanted during cataract surgery to replace the removed lens.Go to Top
Iris
The colored ring of tissue suspended behind the cornea and immediately in front of the lens. It regulates the amount of light entering the eye by adjusting the size of the pupil.Go to Top
J
Jaeger Test
Measurement of visual acuity at the reading distance.Go to Top
K
Keratitis
Inflammation of the cornea. Keratitis may be deep, when the infection causing it is carried in the blood or spreads to the cornea from other parts of the eye, or superficial, caused by bacterial or viral infection or by allergic reaction. Burns of the cornea, such as those produced by chemicals or ultraviolet rays, also give rise to a form of keratitis.Go to Top
Keratoconus
A degenerative corneal disease in which the cornea thins and becomes conical rather than spherical in shape.Go to Top
Keratometry
Assessing the eye's shape to check for astigmatism or other corneal irregularities.Go to Top
L
Lacrimal Gland
The small, almond-shaped structure that produces tears. It is located just above the outer corner of the eye.Go to Top
Lateral Rectus Muscle
Muscle that moves the eye away from the nose.Go to Top
Laser In-Situ Keratomileusis (LASIK)
A medical procedure in which a doctor uses an excimer laser to reshape the cornea under a flap of corneal tissue.Go to Top
Lazy Eye
Also know as amblyopia, a condition of diminished visual acuity in the absence of any detectable anatomic or physiologic cause.Go to Top
Legal Blindness
In the United States, (1) visual acuity of 20/200 or worse in the better eye with corrective lenses (20/200 means that a person must be at 20 feet from an eye chart to see what a person with normal vision can see at 200 feet), or (2) visual field restricted to 20 degrees diameter or less (tunnel vision) in the better eye.Go to Top
Lens
See crystalline lens.Go to Top
Lenticular Lens
Used primarily for post-cataract lenses, a lenticular lens is one in which the power is in the center of the lens but the edge is a portion of plain glass, so it is easily mounted in a frame. Lenticular lenses are designed to reduce the weight and thickness.Go to Top
Limbus
Circular zone where the cornea joins the sclera.Go to Top
Low Vision
Also called partial sight, low vision is sight that cannot be satisfactorily corrected with glasses, contacts, or surgery. Low vision may be the result of glaucoma, macular degeneration, diabetes, or other eye disorder. Special optical devices may be prescribed to help those with low vision accomplish tasks of daily living.Go to Top
M
Macula
The small, sensitive area of the central retina, providing vision for fine work and reading.Go to Top
Macular Degeneration
See Age-related Macular Degeneration.Go to Top
Medial Rectus Muscle
Muscle that moves the eye toward the nose.Go to Top
Microcornea
Abnormally small cornea.Go to Top
Microkeratome
A small instrument used to cut the cornea during LASIK.Go to Top
Migraine
Type of headache that usually occurs on one side of the head and which may be accompanied by visual disturbances, such as sparkles and spots before the eyes.Go to Top
Mirrored Lens
Also know as ski type coating. Mirrored coatings protect eyes from glare and from the sun's infrared rays. The lenses come in a variety of colors to enhance your visual performance.Go to Top
Monocular
Pertaining to one eye.Go to Top
Monovision
Usually accomplished with contact lenses, monovision corrects one eye for distance (usually the dominant eye) and the other eye for near vision. This is a common solution for people having presbyopia but not wanting to use reading glasses or wear bifocal lenses.Go to Top
Multifocal Lens
Eyeglass lens incorporating two or more different powers.Go to Top
Myopia
Also known as nearsightedness. It is the inability to see clearly at a distance as a result of an eyeball that is too long or cornea which is too steep. Nearsightedness can be inherited or could be caused by the stress of concentrating for long periods on close work.Go to Top
N
Near Point
Denotes distance used in conventional reading, generally considered 16 inches or 40 centimeters.Go to Top
Nearsightedness
Nearsightedness (Myopia) is the inability to see clearly at a distance. It's the result of an eyeball that is too long or whose outside surface (the cornea) is too curved. Nearsightedness can be inherited or caused by the stress of concentrating for long periods on close work.Go to Top
No-Line Lens
Also known as progressive lenses or blended lenses, multifocal (bifocal and trifocal) lenses that have no line separating the distance portion from the near portion of the lens. The power gradually changes from distance correction to intermediate vision (at arm's length), to near vision (at reading distance).Go to Top
Nystagmus
Involuntary rapid and repetitive movement of the eyes.Go to Top
O
Occupational Lens
Any lens prescribed primarily for a specific visual task at work, or for participation in a hobby, sport, or other leisure activity. Usually applied to special design multifocals, but any lens can serve as an occupational lens.Go to Top
Ocular
Pertaining to or depending on the eye.Go to Top
Ocular Hypertension
A condition where the intraocular pressure of the eye is above normal. A recent study (the Ocular Hypertensive Treatment Study, or OHTS) indicated that ocular hypertension may be the precursor to glaucoma.Go to Top
OD
Latin abbreviation for right eye; abbreviation for Doctor of Optometry.Go to Top
Ophthalmic
That which pertains to the eye.Go to Top
Ophthalmologist
A doctor of medicine who is both a medical doctor and eye surgeon. The ophthalmologist is licensed to perform surgery, conduct eye exams, treat disease, and prescribe medication, as well as prescribe corrective lenses (glasses or contacts).Go to Top
Ophthalmology
The medical specialty encompassing the anatomy, functions, diseases and treatment of the eye.Go to Top
Ophthalmoscopy
An exam of the retina. The doctor looks through a device with a special magnifying lens that provides a narrow view or a wide view of the retina.Go to Top
Optic Nerve
The bundle of more than a million nerve fibers that carry visual messages from the retina to the brain.Go to Top
Optometrist
A doctor of optometry (OD) who is licensed to examine eyes for the prescription and fitting of corrective lenses (glasses and contact lenses). An optometrist also specializes in the exam, diagnosis, treatment and management of diseases and disorders of the visual system, the eye and associated structures, as well as diagnosis of related systemic conditions.Go to Top
Optometry
The profession of examining, diagnosing, managing and treating eye diseases and defects of the visual system and associated structures.Go to Top
Orthokeratology
Also knowns as CRT. Fitting of hard contacts of differing curvature to achieve a temporary change in the shape of the cornea, temporarily correcting a refractive error.Go to Top
Orthoptics
Also call Vision Therapy, the science of correcting defects in binocular vision resulting from defects in optic musculature or faulty visual habits.Go to Top
P
Palpebral Fissure
The space between the upper and lower eyelids when the eyes are open.Go to Top
Palpebrum
Eyelid.Go to Top
Pathology
Structural and functional deviations from the normal that consitute disease or characterize a particular disease.Go to Top
Peripheral Vision
Side vision or what an eye can see to the side while looking straight ahead.Go to Top
Photochromic Lens
Photochromic lenses darken automatically when exposed to ultraviolet light, specifically sunlight, and lighten with reduced exposure to sunlight.Go to Top
Photokeratitis
Sunburn of the cornea caused by exposure to ultraviolet radiation. Symptoms of photokeratitis include pain, a sandy gritty sensation, blurred vision, and light sensitivity. When caused by the increased UV exposure from reflections off snow it is called "snow blindness."Go to Top
Photorefractive Keratectomy (PRK)
A surgical procedure in which the doctor uses an excimer laser to reshape the cornea without creating a flap (as is done in LASIK) to correct vision problems.Go to Top
Pinguecula
A yellowish, thickened lesion on the conjunctiva.Go to Top
Plano Lens
A term to describe a lens without prescription. The term is most often applied to nonprescription sunglasses or contact lenses that are worn for cosmetic purposes only. Also, used to describe no curvature or flat lens.Go to Top
Plastic Lens
Refers to non-glass lenses, which are impact resistant and lightweight. Plastic lenses are almost half the weight of glass in the same prescription.Go to Top
Polarized Lens
Available in glass and plastic, polarized lenses are sun lenses that protect against reflected glare from water, snow or shiny surfaces. Polarized lenses are considered premium sun lenses. The block UVA, UVB, and UVC radiation.Go to Top
Polycarbonate Lens
More durable than regular plastic, polycarbonate lenses are very lightweight. They also have greater impact resistance than any other lens material, making it the lens of choice for sports eyewear, children or active lifestyles.Go to Top
Posterior Chamber
Filled with aqueous fluid, the space between the back of the iris and the front face of the vitreous.Go to Top
Presbyopia
Usually first noticed around 40 years old, it refers to the reduced accommodative ability of the eye. It happens as the crystalline lens stiffens with age or due to a disease state. The effects of presbyopia are usually overcome with the use of reading glasses or bifocals.Go to Top
Prism
A wedge shaped piece of glass or plastic having a base, apex and apical angle. A prism deviates light towards the base (which makes the image appear to shift towards the apex). Prism may be prescribed to help the eyes work together or to reduce or eliminate double vision due to an eye misalignment.Go to Top
