20/20 Vision
Normal visual acuity; upper number is the standard distance between the tested eye and the eye chart, and the lower number is the distance at which the tested eye can see the same standard-sized letters as a normal eye at 20 feet.
Abduction
Eye rotation away from the midline.
Aberration
Blurred or distorted image quality resulting from the physical properties of an optical device (ie, lens)
Acanthamoeba Keratitis
Acanthamoeba Keratitis is a rare but serious infection of the eye that can result in permanent visual impairment or blindness. This infection is caused by a microscopic, freeliving ameba (single-celled living organism) called Acanthamoeba. Acanthamoeba causes Acanthamoeba Keratitis when it infects the transparent outer covering of the eye called the cornea. Acanthamoeba are very common in nature and can be found in bodies of water (for example, lakes and oceans), soil, and air. Anyone can get acanthamoeba keratitis, but it's most common in people who wear soft contact lenses. You have a greater risk of this condition if you: Swim or shower with contact lenses on or clean your contact lenses with tap water instead of disinfectant solution.
Accommodation
The eye’s increase in optical power in order to maintain image clarity as objects are moved closer
ADD Power
Additional lens power associated with your multifocal, bifocal, or progressive lens prescription needed to make it easier for you to read.
Adduction
Eye rotation toward the midline
Adherence
Refers to the extent to which a patient follows a doctor’s treatment regimen without close supervision
Adjunctive Therapy
Additive treatment or medication that enhances the benefit of another treatment or medication
Age-related
macular degeneration
Group of conditions that include deterioration of the macula, resulting in a loss of sharp central vision; the most common cause of decreased vision after 50
Alacrima
Lack of tear production
Albinism
Lack of pigment in the eyes, hair, and skin, which is usually associated with decreased visual acuity
Allergen
An antigen that creates an allergic or hypersensitivity response
Allergic Conjunctivitis
Inflammation of the conjunctiva from hypersensitivity to allergens
ALT Surgery
Argon laser trabeculoplasty; surgical procedure that uses a laser to create small burns in the trabecular meshwork to lower intraocular pressure
Amblyopia
Also called lazy eye. Decreased vision in one eye that leads to the use of the other eye as the dominant eye. A problem most commonly associated with children.
Angle-closure glaucoma
Rise in intraocular pressure due to aqueous fluid behind the iris being unable to pass through the pupil; patients with anatomically narrow angles are predisposed to this condition
Anopsia
Loss of vision, particularly to part of the visual field
Anterior Chamber
Space between the iris and innermost corneal surface that is filled with fluid
Anti-Reflective
(A/R coating)
A lens treatment for your glasses that helps to reduce distracting glare and eye fatigue by reducing the amount of light reflecting off the lens surface and making the lenses appear clearer. Your eyes will also be more visible behind the lenses
Aphakia
Absence of the eye’s crystalline lens, such as after cataract extraction
Applanation Tonometer
Instrument that flattens the cornea to measure intraocular pressure
Aqueous Humor
Clear fluid that fills the space in the eye between the cornea and the lens; maintains intraocular pressure and provides nourishment to the cornea, iris, and lens
Aqueous Outflow
Passage of aqueous fluid through the anterior chamber angle structures
Artificial Tears
Eyedrops with similar consistency to natural tears to alleviate Dry Eye symptoms
Astigmatism
Refractive error that prevents the eye from focusing sharply, usually resulting from an abnormally shaped corneal surface; correctable by eyeglasses, contact lenses, or refractive surgery
Axis
The axis indicates the angle (in degrees) between the two meridians of an astigmatic eye. The axis is defined with a number from 1 to 180.
Bacterial Conjunctivitis
Inflammation of the conjunctiva caused by a bacterial infection; usually contagious.
Bacterial Conjunctivitis
Inflammation of the conjunctiva caused by a bacterial infection; usually contagious
Basal Lamina
Innermost layer of the choroid, directly under the retina; damage to the basal lamina is responsible for many bleeding disorders of the macula area
Base Curve
A number usually between 8 and 10 that conforms to the shape of your eye with your contact lens prescription.
Bell’s Palsy
Condition in which muscles of the brows, eyelids, and mouth are paralyzed by damage to the 7th cranial nerve; may cause affected eyelids to remain open, resulting in corneal drying
BID
Twice daily
Bifocals
Eyeglasses that incorporate lenses of 2 different powers; allows for both near and far distance sight without changing eyewear
Binocular
Referring to or affecting both eyes
Bleb
Flap of tissue created to cover a sclero-corneal drainage channel during glaucoma surgery; enhances fluid outflow from the eye
Blepharitis
Inflammation of the eyelids; may be caused by infection or allergy
Blepharoconjunctivitis
Inflammation of the conjunctiva
Blepharospasm
Sudden, involuntary spasm causing uncontrolled blinking and squeezing of the eyelid
Blind Spot
Non-seeing area within every visual field; caused by absence of photoreceptors where the optic nerve enters the eye
Blindness
Inability to see
Blink Reflex
Periodic contraction of the eye muscles approximately every 5 seconds, causing the eyelid to close over the eye, spreading tears over the eye and limiting light entering the eye
Blue IQ™
Blue light blocking lenses offered at LensCrafters®. They offer two different options: one called Blue IQ™ lenses, which block about 52 percent of blue light, and another called Blue IQ Clear™ lenses, which block about 20 percent of blue light.
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Blue Light
Blue light is all around us. It comes primarily from the sun and it's what makes the sky look blue. Artificial blue light is also emitted by devices like computers, smartphones, flat-screen televisions LED lights, and energy-efficient light bulbs.
Capsulotomy
Incision to remove part of the lens capsule.
Capsulotomy
Incision to remove part of of the lens capsule
Cataracts
A cataract is a clouding of the crystalline lens of the eye that makes it hard for light to pass through and be focused properly. In a normal eye, the crystalline lens is almost transparent, however injury, age or disease can cause the lens to eventually loose its clarity. When the lens becomes 'opaque', it is called a cataract. Treatable by surgery.
Central Retinal Artery
First branch of the ophthalmic artery; provides nutrients to the inner two-thirds of the retina.
Central Retinal Vein
Collects retinal venous blood drainage and exits through the optic nerve.
Chalazion
Inflamed bump in the eyelid's meibomian gland.
Chemosis
Swelling of the conjunctiva.
Choroid
Vascular Layer of the eye between the retina and sclera, providing nutrients to the outer layers of the retina.
Choroiditis
Inflammation of the choroid.
Chronic Dry Eye
Corneal/conjunctival dryness due to deficient tear production; keratoconjunctivitis sicca, Dry Eye syndrome.
Ciliary Body
Tissue in the eye that is involved in lens accommodation, intraocular pressure control, and producing the aqueous humor.
Collagen Cross-linking
Collagen Cross-linking is procedure done to slow down the progression of Keratoconus. This treatment uses a combination of specially formulated eye drops and precisely applied UV light to create new bonds between the collagen fibers in your cornea. This strengthens and firms a cornea that has been weakened and thinned by keratoconus.
Color Deficiency
A lack of ability to distinguish certain colors. Commonly called "color blindness", the most common form of color deficiency is the inability to distinguish shades of red and green.
Compliance
Refers to a patient following a doctor's treatment regimen.
Congenital Glaucoma
High intraocular pressure, hazy corneas, and large eyes in children from newborn to 6 months old; developmental abnormalities prevent normal fluid drainage from the eye; requires surgical intervention.
Conjunctiva
Mucous membrane covering the outer surface of the eyeball (except the cornea) and inside surface of the eyelids.
Conjunctival Hyperemia
Redness of the conjunctiva; associated with all types of conjunctivitis.
Conjunctival Sac
Pocket of conjunctiva between the upper eyelid and eyeball and lower eyelid and eyeball that permits the eyeball to rotate freely.
Conjunctivitis
An eye condition caused by the inflammation of the conjunctiva, or clear membrane covering the white part of the eye and lining of the eyelids. The eyes will often appear swollen and red while also feeling gritty. It can be bacterial, viral, or allergic and could be contagious. Call or see your doctor to treat conjunctivitis.
Contact Lens
Small disc worn on the cornea or sclera, providing visual correction of refractive errors.
Convergence
Moving both eyes towards each other to maintain single binocular vision of an approaching object.
Corectopia
Displacement of the pupil from its normal position.
Cornea
Transparent front of the eye covering the iris, pupil, and anterior chamber; provides the bulk of the eye's optical power.
Corneal Abrasion
Scraped area of the cornea accompanied by superficial tissue loss.
Corneal Apex
Central 3-5 mm where the cornea has the greatest curvature.
Corneal Edema
Hazy and swollen cornea.
Corneal Erosion
Loss of the outer layer of the cornea because it fails to adhere to the Bowman's membrane.
Corneal Hydrops
Corneal hydrops is a complication of advanced keratoconus and is characterized by sudden onset of severe corneal opacification because of edema. The edema occurs from a spontaneous break in Descemet's membrane (one of the 5 layers of the cornea) because of the weakened cornea, leading to a sudden and painful decrease in visual acuity.
Corneal Staining
Use of dye such as fluorescein to reveal corneal epithelial defects.
Corneal Transplant
Replacement of damaged or diseased cornea with donor corneal tissue.
Corticosteroid
Steroid used to treat inflammatory and allergic diseases.
Crystalline Lens
The eye's natural lens located directly behind the iris. It has the ability to change shape to focus light rays onto the retina.
Cup
Optic cup; depression in the center of the optic disc that normally occupies less than one-third of the dis diameter.
Cup-to-disc Ratio
Evaluates the progression of glaucoma by indicating the percentage of the disc occupied by the optic cup.
Cupped Disc
Abnormal enlargement of the optic cup, usually due to a long-term increase in intraocular pressure.
Cylinder Correction
Use of a lens that produces different refractive power in each meridian; used to correct astigmatism.
Cystoid Macular Edema
Retinal swelling and cyst formation ion the macular area, can result in temporary or permanent decrease in vision.
Dacryocystitis
Inflammation of the tear sac, often associated with poor tear drainage.
Depth Perception
Awareness of relative spatial location of objects; perception of nearness and farness.
Diabetic Macular Edema
The leaking of retinal blood vessels into the macula in patients with diabetes, causing the macula to swell, which can temporarily or permanently decrease central vision.
Diabetic Retinopathy
Progressive retinal changes that accompany diabetes mellitus; this can progress from background retinopathy to proliferative retinopathy, which includes abnormal new blood vessels and fibrous tissue development.
Diameter
The distance from one side of the lens to the other, usually around 13 to 15 millimeters that is associated with the size of your contact lenses.
Dilation
Widening of the pupil.
Diopter
Perception of two images from one object; double vision
Disc
Optic disc; ocular end of optic nerve
Dry Eye Syndrome
An eye condition that presents itself as itching, burning, and irritation of the eyes, is often called "dry eye syndrome". It is one of the most common problems treated by eye care professionals. It is usually caused by the breakdown (or deficiency) in the tears that lubricate the eyes. As we age, our bodies produce less oil to seal the eyes' watery layer. Hot, arid climates, air conditioning, certain medicines and irritants such as cigarette smoke can all increase dryness of the eye. Your eye care professional might prescribe "artificial tears" or other eye drops to help alleviate the problem.
Dyscoria
Distorted shape of pupil.
Epicanthal Fold
Vertical skin fold at each side of the nose; hides the caruncle; present in infants before nose bridge is developed.
Epiphora
Overflow of tears down the face caused by poor tear drainage, excessive tearing, or outward turning of the lower eyelid.
Erythema
Abnormal skin redness caused by capillary congestion under the skin.
Esotropia
Eye misalignment in which one eye turns inward while the other stays fixed straight ahead.
Evisceration
Procedure that removes the contents of the eyeball, leaving behind the sclera shell and, sometimes, the cornea; usually for reducing pain in a blind eye.
Exotropia
Eye misalignment in which one eye turns outward while the other stays fixed straight ahead.
Exposure Keratitis
Corneal irritation or inflammation caused by corneal drying due to incomplete closure of the eyelid.
External Diseases
Diseases that affect the cornea, sclera, conjunctiva, or eyelids.
Eye
Sense organ for sight.
Eyelash
One of the stiff hairs at the margin on the eyelid.
Eyelid
Structure covering the front of the eye that protects it, limits the light entering in, and distributes the tear film over the corneal structure.
Eyewall
The sclera and the cornea.
Farsightedness
Refractive error that allows the eye to see clearly at a distance, but close-up images are blurred; hyperopia
Femtosecond Laser
Short-pulse laser that is used to create corneal flaps in refractive surgery.
Flashes
Flashes are a visual sensation that can look like a camera flash going off or a lightning streak in your vision. Flashes occur because the vitreous or "jelly" is tugging on the retina. If the vitreous tugs too hard, it may cause a vision threatening event called a retinal tear or detachment. If you notice a sudden increase in the number of flashes you see, call your eye care professional.
Floaters and Spots
A generalized term used to describe small specks moving subtly but noticeably in your field of vision. A floater or a spot is likely a tiny clump of gel or cells in the vitreous — the clear, jelly-like fluid inside your eye. Aging, eye injury and breakdown of the vitreous are the main causes of floaters and spots. If you notice a sudden increase in the number you see, call your eye care professional.
Fluorescein
Colored dye that illuminates; used on the cornea to identify damage.
Focal Point
Position on the principal axis of a lens system where parallel light rays are brought to a point of focus.
Focal Point
Position on the principal axis of a lens system where parallel light rays are brought to a point of focus.
Follicles
Tiny elevations on the undersurface of the eyelids; associated with viral conjunctival inflammation.
Foreign Body Sensation
The feeling of something in the eye; can be caused by an actual foreign body in the eye or by various damage or conditions.
Fovea
A tiny spot in the center of the retina that contains only cone cells. This area is responsible for our sharpness of vision.
Fundus
Interior posterior surface of the eyeball which includes the retina, optic disc, macula, and posterior pole.
Gerontoxin
Degenerative change that produces a white ring-shaped deposit of fat near the peripheral edge of the cornea; typically in patients over 60.
Glare Test
Clinical test that determines the extent to which a bright light shined in the eye changes visual acuity; evaluates the degree of visual impairment caused by a cataract.
Glaucoma
A common cause of preventable vision loss that is due to damage to the optic nerve, the nerve that carries visual information from the eye to the brain. Treatable by prescription drugs or surgery.
Globe
The eyeball; a sensory organ that uses light to transmit visual information to the brain; 3 major layers in the globe include corneo-sclero, uvea, and retina.
Goblet Cell
Large mucous glands in the conjunctiva that secrete mucin, a component of precorneal tear film; can be damaged in Dry Eye sydrome.
Gonioscopy
Test that examines the anterior chamber angle structures through a special lens with a slit lamp.
Goniotomy
Surgical procedure that is often used to treat congenital glaucoma; it consists of an incision in the trabecular meshwork.
Graves Disease
Symptoms of the eye that may result with excessive thyroid-related concentration, including eyelid retraction, eyelid lag, corneal drying, and optic nerve inflammation.
Halo
Hazy ring seen around lights; can be a sign of a refractive error or optical defect such as cataract.
Herpes Keratitis
Eye infection caused by the herpes simplex virus. Results in inflammation and ulcers.
Heterochromia of the Iris
Having a different color iris in each eye.
High(er) Index
A dense lens material that results in thinner, lightweight lenses than standard plastic. Index refers to index refraction which is the speed that light travels through the lens. Higher index lenses are available from 1.56 to 1.74 (the higher the number, the thinner the lens). They benefit people with stronger prescription eyeglasses.
Histamine
Chemical that creates an allergic or inflammatory response.
Hordeolum
Acute infection of oil glands of the eyelid; externally, also known as a stye; internally (in the meibomian glands), also known as a chalazion, if chronic.
Hyperemia
Clinical sign; increased blood flow; usually refers to eye redness due to increased blood flow to the conjunctival blood vessels.
Hyperopia
A condition where they eye is too short for its optical power causing distant objects to be seen clearly, yet objects close up are seen less clearly. Also commonly referred to as "farsighted."
Hypertropia
Functional defect in which one eye deviates upward while the other remains straight and fixates normally.
Hyphema
Clinical sign; blood in the anterior chamber, often following blunt trauma to the eyeball.
Hypotropia
Functional defect in which one eye deviates downward while the other remains straight and fixates normally.
Intraocular Lens
Lens that may be surgically implanted to replace the eye's natural lens.
Intraocular Pressure (IOP)
The pressure of fluid within the eye; elevated IOP is a treatable risk factor for glaucoma.
Iridectomy
Removal of a portion of iris tissue.
Iris
Pigmented tissue behind the cornea that gives the eye its color and allows light to enter the eye by controlling the size of the pupillary opening; part of the uveal (middle) layer of the eye.
Iritis
Inflammation of the iris, causing pain, tearing, blurring, small pupil, and red congested eye.
Isopia
Equal vision in both eyes.
Keratectomy
Surgical removal of corneal tissue.
Keratitis
Corneal inflammation; can be caused by a variety of infections, injuries, and unknown causes.
Keratoconjunctivitis Sicca
Corneal and conjunctival dryness due to deficient tear production; Dry Eye syndrome.
Keratoconus
– Keratoconus is a condition that causes progressive weakening, thinning and cone-like bulging of the cornea. This irregularity in the shape of the cornea causes light rays hitting the cornea to become out of focus and results in blurry and distorted vision that cannot be corrected by wearing glasses. Distorted vision from Keratoconus can be corrected by special gas permeable contact lenses. Corneal damage from Keratoconus is not reversible however its progression can be slowed down and even halted completely by a procedure called Collagen Cross-linking. In severe cases of keratoconus, transplantation of the cornea may be necessary.
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Keratolysis
Corneal melt; superficial corneal layers that "melt" away; often associated with severe inflammation, Dry Eye, or rheumatoid arthritis.
Keratoplasty
Surgical procedure on the cornea that usually refers to a corneal graft (replacing damaged corneal tissue with donor tissue).
Keratotomy
Any incision into the cornea (surgical procedure).
Lacrimal Gland
Almond-shaped gland located above the eyeball in the upper outer region that produces tears.
Lacrimation
Tear production; crying.
Laser
Acronym for Light Amplification by Stimulated Emission of Radiation; a high-energy light source that can cut, burn, or dissolve tissues for clinical procedures; used in many eye care procedures such as refractive surgery, treatment of diabetic retinopathy and macular degeneration, and removal of trabecular meshwork in glaucoma patients.
LASIK
LAser in Sltu Keratomileusis; refractive surgery in which the cornea is reshaped to change its optical power; corrects myopia, hyperopia, and astigmatism.
Legal Blindness
Visual Acuity of 20/200 or less, or visual field reduction to 20 degrees or less (in the better eye).
Lens
Any transparent material (often glass) that can bend light rays predictably.
Lensectomy
Removal of the eye's natural lens.
Limbus
Area where the cornea joins the sclera and the bulbar conjunctiva attaches to the eyeball.
Lipiflow
– Lipiflow is a heat treatment for Meibomian Gland Dysfunction. It provides a warm and gentle heat to the eyelids while simultaneously applying a gentle massage. This combination effectively removes the blockages in the meibomian glands and allows them to secrete the clogged oil. After a session of LipiFLow treatment, the glands will be able to resume its natural production of oil for the tear film.
Low-tension Glaucoma
Also known as Normal-tension glaucoma; type of open-angle glaucoma in which a patient exhibits signs such as progressive disc cupping and visual field loss, but with normal intraocular pressure.
Macropsia
Distorted vision in which objects appear larger than normal.
Macula
The part of the retina responsible for the sharp, central vision needed to read or drive.
Macular Degeneration
A group of conditions that include a deterioration of the macula causing a loss of central vision needed for sharp, clear eyesight. It is a leading cause of vision loss and blindness in those 65 years of age and older. Macular Degeneration is also called AMD or ARMD (age-related macular degeneration).
Macular Edema
Swelling and cyst formation in the macula; can temporarily or permanently decrease vision.
Maculopathy
Abnormality of the macula.
Madarosis
Loss of eyelashes often caused by chronic blepharitis.
Magnification
Increased image size created through the use of optical devices.
Meibomian Gland
Oil gland in the eyelid tissue that secretes the outer portion of the tear film; prevents rapid tear evaporation and tear overflow.
Microbial Keratitis
Corneal infection from overuse of contact lenses; caused by microorganisms.
mm Hg
Millimeters of mercury; units used to measure intraocular pressure.
Moll Glands
Sweat glands near the eyelash follicles; infection can cause a stye.
Monocular
Referring to one eye.
Multi-Focal Lenses
Multi-focal lenses let you focus on two or more distances through the same lens (usually distance, intermediate, and near). Also known as Bifocals, Trifocals, and Multifocals.
Myopia
A condition cuased by an overpowered eye, which has too much optical power for its length, where distant objects appear less clearly and those objects up close are seen clearly. Also commonly referred to as "nearsighted."
Narrow-angle Glaucoma
Rise in intraocular pressure caused by narrow anterior chamber angles that prevent aqueous drainage.
Nasolacrimal Duct
Tear drainage channel from the lacrimal sac to the mucous membrane of the nose.
Nasolacrimal Duct Obstruction
Is a blocked tear duct that occurs when your nasal passageways cannot properly drain tear liquid from your eyes. You may have crusty, itchy, irritated or watery eyes. Sometimes, babies are born with blocked tear ducts.
NCLE
National Contact Lens Examiners are certified professionals in Optometry who fit and work with contact lenses.
NDC number
US National Drug Code; a standard code used to to identify FDA-approved drugs and biologicals.
Nearsightedness
Refractive error that allows the eye to see close-up objects clearly, but distance vision is blurred; myopia.
Neurotrophic Keratitis
Corneal inflammation resulting from trauma or damage to corneal nerves; leads to cornea anesthesia.
Night Blindness
Poor visual adaptation to the dark, resulting in reduced vision in low light; usually indicates defect in retinal rods.
Nyctalopia
Commonly called "night blindness," this is a condition that presents as impaired vision in dim light or darkness.
Nystagmus
A functional defect in which the patient displays involuntary oscillating eye movements that are faster in one direction than the other.
Ocular Biometry
Test that measures distance between various ocular structures (usually with A-scan or B-scan ultrasound instruments).
Ocular Hypertension
Elevated IOP, but with no evidence of optic disc or visual field changes; potential (but not definite) glaucoma suspect.
Ocular Surface
Disease Index© (OSDI©)
A valid and reliable instrument of 12 questions for measuring Dry Eye Disease and its effect on vision-related function.
OD
Right eye.
Open-angle Glaucoma
The most common type of glaucoma caused by the slowing of normal aqueous outflow from the eye; can result in gradual, irreversible vision loss.
Ophthalmologist
Doctor of medicine (MD) or doctor of osteopathic medicine (DO) specializing in diagnosis and treatment of eye diseases and disorders.
Ophthalmology
Medical specialty dealing with function and disease of the eye.
Ophthalmoscopy
Use of an ophthalmoscope to examine the internal structures of the eye.
Optic Nerve
The second cranial nerve that is the largest sensory nerve of the eye; carries sight information from the retina to the brain for processing.
Optic Neuropathy
Abnormality or degeneration of the optic nerve, not due to inflammation.
Optician
Vision care professional who makes and adjusts optical aids such as eyeglasses.
Optomap
Retinal imaging that captures more than 80% of your retina in one panoramic image that allows your Optometrist to provide you with the most comprehensive eye exam possible by detecting underlying eye diseases and monitor treatment for existing ocular diseases.
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Optometrist
Doctor of optometry (OD) who specializes in vision problems and treatments.
Optometry
Vision care specialty that deals with the detection and management of ocular disease.
Orbit
Socket; cranial cavity of the skull that contains the eyeball.
Orthokeratology
“Ortho-K” is a lens fitting procedure that uses specially designed rigid gas permeable (RGP) contact lenses to change the curvature of the cornea to temporarily improve the eye's ability to focus on objects. The lenses are worn at night to give clear vision during the day
OS
Left eye.
Outflow (aqueous)
Passage of aqueous fluid out of the eye through the anterior chamber angles.
Pachymetry
Test to measure corneal thickness
Palpebral Fascia
Fibrous membrane that forms a protective layer between the eyelid and the bony orbit (socket)
Paraoptometric
Certified allied health professional in optometry; three levels are certified by CPO®: CPOA®, and CPOT®
Perennial Allergies
Also known as year-round allergies, these are usually due to indoor allergies such as dust mites or mold
Periocular
Area surrounding the eyeball
Peripheral Vision
Side vision, created by stimuli falling on retinal areas that are far from the macula
Phacoemulsification
Surgical procedure that uses ultrasound vibration to break up a cataract, making it easy to suction out of the eye
Phakic
Refers to an eye that has its natural lens
Photochromic Lenses
Refers to lenses that automatically change from clear to dark in the presence of ultraviolet (UV) radiation.
Photophobia
Abnormal sensitivity to light; associated with discomfort and excessive tearing; often due to iritis or keratitis
Photopsia
Sensation of light or flashes from mechanical or electrical irritation of the retina (not from a light stimulus)
Photorefractive Keratectomy (PRK)
Refractive surgery that reshapes the corneal curvature with a laser after the surface of the cornea has been removed
Pink Eye
Conjunctivitis; inflammation of the conjunctiva that is usually viral in origin; symptoms include discharge, grittiness, redness, and swelling
Plastic 1.50
This is a lens material often used for minor prescriptions. Very few lenses are made from glass today, since glass is heavier, thicker, and can shatter. Also referred to as standard index or by the brand name CR-39.
Polarized Lenses
This type of lens includes an invisible “polarized” filter that helps to cut down on blinding glare from reflective surfaces like water and snow for increased visual acuity (sharpness) in bright light conditions.
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Pollen
Microspores of seed plants that can induce allergic or hypersensitivity reactions in some people
Polycarbonate Lenses
A lens material that is thinner, lighter, and more impact resistant than standard plastic. Polycarbonate lenses are the standard for children’s eyewear.
Posterior Capsular Opacification
After cataract surgery, the rear lens capsule can cloud over; needs removal to improve vision
Posterior Chamber
Space between the back of the iris and the front of the vitreous
Presbyopia
Condition in which the aging crystalline lens (at around age 40) becomes less able to change shape to focus light at all distances, especially near vision. Presbyopia can be corrected with reading glasses, bi-focal glasses, or progressive lenses. Additional symptoms include eyestrain, headaches, and squinting.
Primary Open-angle Glaucoma
The most common type of glaucoma caused by the slowing of normal aqueous outflow from the eye; can result in gradual vision loss
Prism
Prism correction is used in eyeglasses for some people with diplopia, or double vision. The prism helps align the two images, so that only one image is seen.
PRN
As needed (as medication dosing)
Progressives
Bi-focal or multi-focal lenses with no visible lines where the lens power gradually changes from distance to near. Also called PALs (Progressive Addition Lenses).
Pruritus
Itching
Pseudoexfoliation
Unknown deposits appearing on the lens surfaces and other ocular structures; often associated with high intraocular pressure
Pterygium
A raised growth on the eye that is most often directly related to over-exposure to the sun. Dry, dusty conditions may also contribute to development of these growths. Protecting your eyes from UV radiation is a critical preventive measure.
Ptosis
Sagging upper eyelid
Puff Tonometer
Device that measures intraocular pressure by blowing a puff of air against the cornea to flatten it
Punctal Plug
Plastic plug inserted into the punctum to prevent tear drainage, preserving tears to keep the eye moist
Punctate Keratitis
Corneal disease characterized by small corneal lesions of unknown origin
Pupil
Black circular opening in the center of the iris that varies in size to regulate the amount of light that enters the eye
Pupillary Distance
Pupillary distance (PD) is the distance between the pupils of your two eyes. It is an essential measurement when buying a new pair of prescription eyewear. For greatest comfort and clarity, these measurements should be taken by the optician involved in manufacturing the spectacles.
Pupillometer
An instrument used to measure the distance between pupils. This measurement is used to position the eyeglass prescription correctly in front of the eye.
QD
Once daily
QID
Four times daily
Refraction
Test to determine an eye’s refractive error and the best corrective lenses to be prescribed.
Refractive Error
Optical defect in an unaccommodating eye; correctible with surgery, eyeglasses, or contact lenses
Retina
Light-sensitive tissue in the eye that converts images into electrical impulses that are sent to the brain via the optic nerve to interpret as vision. Consists of layers that include rods and cones.
Retinal Detachment
Separation of the retina from the underlying pigment epithelium; usually caused by a retinal tear that leaks fluid from the vitreous and separates the retina
Retinal Hole
Retinal holes and tears are small breaks in the retina. Usually holes do not mean you will have serious vision problems right away. However, retinal holes and tears may cause problems if they allow fluid to seep behind the retina and cause the retinal layers separate from each other or detach from layers underneath.
Retinal Vein Occlusion
Blockage of blood flow through the central retinal vein, causing a decrease in vision
Retinitis
Inflammation of the retina
Retinoblastoma
Malignant tumor that develops from retinal visual cells
Retinopathy
Any noninflammatory degenerative disease of the retina
Retinoscopy
Test that measures the eye’s refractive error
Rigid Gas Permeable “RGP” Lenses
Gas permeable contact lenses are rigid lenses made of durable plastics that allow oxygen to pass through the lens.
Rods and Cones
These are cells inside the eye used by the retina to process light. Rods are used for low light levels (night vision), cones are used for sharp visual acuity and color perception.
Schirmer Test
Measures tear production with filter paper strips
Schlemm’s Canal
Channel in the corneo-scleral junction that carries aqueous fluid from the anterior chamber to the bloodstream
Sclera
Opaque protective outer layer of the eye (“the white”) that connects to the cornea and the sheath of the optic nerve
Scleral Lenses
Scleral lenses are large-diameter gas permeable contact lenses that vault over the cornea (the clear front of the eye) and rest over the sclera (the white of the eye). The scleral lens provides a smooth optical surface that works to correct vision problems caused by keratoconus and other irregular cornea problems.
Scleritis
Inflammation of the sclera, often painful
Seasonal Allergies
Allergies, such as hay fever, that are seasonal in nature (eg, springtime or fall)
Single-Vision
Types of lenses that correct one vision problem, like near or far-sightedness.
Sjögren Syndrome
Chronic autoimmune disease often characterized by dry eyes, dry mouth, and arthritis
Slit Lamp
Microscope used to examine the eye; shows the cornea, lens, and clear fluids and membranes in layered detail
SLT Surgery
Surgical procedure in which a laser is used on the trabecular meshwork to increase aqueous outflow, reducing intraocular pressure
Snellen Chart
Lettered chart for measuring visual acuity; usually tested at 20 feet (hence, 20/20 vision)
Snellen Chart
This is the commonly seen eye chart often topped by a large letter “E” used in eye examinations. This measures your eye’s visual acuity, or the ability to see sharp detail clearly.
Somnolence
Sleepiness
Sphere
Sphere indicates the amount of lens power prescribed to correct nearsightedness or farsightedness.
Strabismus
Sometimes called “crossed eyes” in young children, this condition is the lack of coordination between the eyes, such as one or both eyes turning in, out, up or down.
Stye
Acute pustular infection of oil glands located in an eyelash follicle
Tachyphylaxis
Rapid decrease in response to a given dose of a drug after repetitive administration.
Tarsal Gland
Oil gland within the eyelid tissue; secretes the outer portion of the tear film to prevent tear evaporation and overflow
Tear Breakup Time
Tests the time between a blink and the development of a dry spot on the ocular surface; less than 10 seconds is abnormal.
Tear Duct
Tear drainage channel from the lacrimal sac to the mucous membrane of the nose.
Tears
Fluid secreted by the lacrimal glands to keep the conjunctiva and cornea moist.
Temporal Pallor
Loss of pinkish tone in the optic disc; usually indicates optic nerve damage.
TID
Three times daily.
Tonometer
Instrument that measures intraocular pressure; each type of tonometer measures pressure through slightly different means.
Toric Lens
An optical device with a cylindrical component to correct astigmatism.
Trabecular Meshwork
Structure inside the eye at the iris-scleral junction of the anterior chamber angle that filters aqueous fluid and controls its exit from the eye through Schlemm’s canal.
Trabeculectomy
Surgical procedure to remove part of the trabecular meshwork to increase the outflow of aqueous fluid to treat elevated intraocular pressure.
Trabeculoplasty
Surgical procedure that uses a laser to burn part of the trabecular meshwork to increase outflow of aqueous fluid to treat elevated intraocular pressure.
Trachoma
Severe, chronic, and contagious infection of the eyelid and cornea caused by a virus; the leading cause of blindness in the world.
Trichiasis
A condition caused by misdirected or abnormally positioned eyelashes. Trichiasis, sometimes caused by entropion causes discomfort and irritation to the eye, and can lead to permanent damage to the cornea and vision loss.
Trifocal
Optical device that incorporates lenses of 3 different powers.
Triplopia
Ocular defect that causes images to appear in triplicate; often caused by an early cataract
Ultraviolet Light
Light with wavelengths between 250 and 400 nanometers; invisible to the naked eye.
Ultraviolet Radiation (UVR)
Commonly referred to as “UV Rays”, these are light waves that consist of both UVA and UVB rays from the sun. Without proper protection, chronic exposure to UV rays can lead to various eye conditions and damage.
UV Protection
Relates to a lens’ ability to filter out harmful rays of the sun. It is recommended that glasses block 100% of both UVA and UVB rays to minimize eye damage from the sun’s rays.
Uvea
Pigmented vascular layers of the eye (iris, ciliary body, and choroid) that contain most of the eye’s blood vessels.
Uveitis
Inflammation of any of the structures of the uvea (iris, ciliary body, or choroid).
Vision
Ability of the eye to receive and transmit light images to the brain, where they are interpreted; the ability to see.
Visual Acuity
Assessment of the eye’s ability to distinguish object details and shape – numerically expressed as 20/20, 20/70, etc.
Visual Field
The full area visible to the eye when fixated straight ahead; measured in degrees.
Vitrectomy
Surgical removal of the vitreous.
Vitreous
Transparent gelatinous mass that fills the back two-thirds of the eyeball between the lens and retina.
Year-round Allergies
Also known as perennial allergies, these are usually due to indoor allergies such as dust mites or mold.
Abduction
Eye rotation away from the midline.
Aberration
Blurred or distorted image quality resulting from the physical properties of an optical device (ie, lens)
Acanthamoeba Keratitis
Acanthamoeba Keratitis is a rare but serious infection of the eye that can result in permanent visual impairment or blindness. This infection is caused by a microscopic, freeliving ameba (single-celled living organism) called Acanthamoeba. Acanthamoeba causes Acanthamoeba Keratitis when it infects the transparent outer covering of the eye called the cornea. Acanthamoeba are very common in nature and can be found in bodies of water (for example, lakes and oceans), soil, and air. Anyone can get acanthamoeba keratitis, but it's most common in people who wear soft contact lenses. You have a greater risk of this condition if you: Swim or shower with contact lenses on or clean your contact lenses with tap water instead of disinfectant solution.
Accommodation
The eye’s increase in optical power in order to maintain image clarity as objects are moved closer
ADD Power
Additional lens power associated with your multifocal, bifocal, or progressive lens prescription needed to make it easier for you to read.
Adduction
Eye rotation toward the midline
Adherence
Refers to the extent to which a patient follows a doctor’s treatment regimen without close supervision
Adjunctive Therapy
Additive treatment or medication that enhances the benefit of another treatment or medication
Age-related
macular degeneration
Group of conditions that include deterioration of the macula, resulting in a loss of sharp central vision; the most common cause of decreased vision after 50
Alacrima
Lack of tear production
Albinism
Lack of pigment in the eyes, hair, and skin, which is usually associated with decreased visual acuity
Allergen
An antigen that creates an allergic or hypersensitivity response
Allergic Conjunctivitis
Inflammation of the conjunctiva from hypersensitivity to allergens
ALT Surgery
Argon laser trabeculoplasty; surgical procedure that uses a laser to create small burns in the trabecular meshwork to lower intraocular pressure
Amblyopia
Also called lazy eye. Decreased vision in one eye that leads to the use of the other eye as the dominant eye. A problem most commonly associated with children.
Angle-closure glaucoma
Rise in intraocular pressure due to aqueous fluid behind the iris being unable to pass through the pupil; patients with anatomically narrow angles are predisposed to this condition
Anopsia
Loss of vision, particularly to part of the visual field
Anterior Chamber
Space between the iris and innermost corneal surface that is filled with fluid
Anti-Reflective
(A/R coating)
A lens treatment for your glasses that helps to reduce distracting glare and eye fatigue by reducing the amount of light reflecting off the lens surface and making the lenses appear clearer. Your eyes will also be more visible behind the lenses
Aphakia
Absence of the eye’s crystalline lens, such as after cataract extraction
Applanation Tonometer
Instrument that flattens the cornea to measure intraocular pressure
Aqueous Humor
Clear fluid that fills the space in the eye between the cornea and the lens; maintains intraocular pressure and provides nourishment to the cornea, iris, and lens
Aqueous Outflow
Passage of aqueous fluid through the anterior chamber angle structures
Artificial Tears
Eyedrops with similar consistency to natural tears to alleviate Dry Eye symptoms
Astigmatism
Refractive error that prevents the eye from focusing sharply, usually resulting from an abnormally shaped corneal surface; correctable by eyeglasses, contact lenses, or refractive surgery
Axis
The axis indicates the angle (in degrees) between the two meridians of an astigmatic eye. The axis is defined with a number from 1 to 180.
Bacterial Conjunctivitis
Inflammation of the conjunctiva caused by a bacterial infection; usually contagious.
Bacterial Conjunctivitis
Inflammation of the conjunctiva caused by a bacterial infection; usually contagious
Basal Lamina
Innermost layer of the choroid, directly under the retina; damage to the basal lamina is responsible for many bleeding disorders of the macula area
Base Curve
A number usually between 8 and 10 that conforms to the shape of your eye with your contact lens prescription.
Bell’s Palsy
Condition in which muscles of the brows, eyelids, and mouth are paralyzed by damage to the 7th cranial nerve; may cause affected eyelids to remain open, resulting in corneal drying
BID
Twice daily
Bifocals
Eyeglasses that incorporate lenses of 2 different powers; allows for both near and far distance sight without changing eyewear
Binocular
Referring to or affecting both eyes
Bleb
Flap of tissue created to cover a sclero-corneal drainage channel during glaucoma surgery; enhances fluid outflow from the eye
Blepharitis
Inflammation of the eyelids; may be caused by infection or allergy
Blepharoconjunctivitis
Inflammation of the conjunctiva
Blepharospasm
Sudden, involuntary spasm causing uncontrolled blinking and squeezing of the eyelid
Blind Spot
Non-seeing area within every visual field; caused by absence of photoreceptors where the optic nerve enters the eye
Blindness
Inability to see
Blink Reflex
Periodic contraction of the eye muscles approximately every 5 seconds, causing the eyelid to close over the eye, spreading tears over the eye and limiting light entering the eye
Blue IQ™
Blue light blocking lenses offered at LensCrafters®. They offer two different options: one called Blue IQ™ lenses, which block about 52 percent of blue light, and another called Blue IQ Clear™ lenses, which block about 20 percent of blue light.
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Blue Light
Blue light is all around us. It comes primarily from the sun and it's what makes the sky look blue. Artificial blue light is also emitted by devices like computers, smartphones, flat-screen televisions LED lights, and energy-efficient light bulbs.
Capsulotomy
Incision to remove part of the lens capsule.
Capsulotomy
Incision to remove part of of the lens capsule
Cataracts
A cataract is a clouding of the crystalline lens of the eye that makes it hard for light to pass through and be focused properly. In a normal eye, the crystalline lens is almost transparent, however injury, age or disease can cause the lens to eventually loose its clarity. When the lens becomes 'opaque', it is called a cataract. Treatable by surgery.
Central Retinal Artery
First branch of the ophthalmic artery; provides nutrients to the inner two-thirds of the retina.
Central Retinal Vein
Collects retinal venous blood drainage and exits through the optic nerve.
Chalazion
Inflamed bump in the eyelid's meibomian gland.
Chemosis
Swelling of the conjunctiva.
Choroid
Vascular Layer of the eye between the retina and sclera, providing nutrients to the outer layers of the retina.
Choroiditis
Inflammation of the choroid.
Chronic Dry Eye
Corneal/conjunctival dryness due to deficient tear production; keratoconjunctivitis sicca, Dry Eye syndrome.
Ciliary Body
Tissue in the eye that is involved in lens accommodation, intraocular pressure control, and producing the aqueous humor.
Collagen Cross-linking
Collagen Cross-linking is procedure done to slow down the progression of Keratoconus. This treatment uses a combination of specially formulated eye drops and precisely applied UV light to create new bonds between the collagen fibers in your cornea. This strengthens and firms a cornea that has been weakened and thinned by keratoconus.
Color Deficiency
A lack of ability to distinguish certain colors. Commonly called "color blindness", the most common form of color deficiency is the inability to distinguish shades of red and green.
Compliance
Refers to a patient following a doctor's treatment regimen.
Congenital Glaucoma
High intraocular pressure, hazy corneas, and large eyes in children from newborn to 6 months old; developmental abnormalities prevent normal fluid drainage from the eye; requires surgical intervention.
Conjunctiva
Mucous membrane covering the outer surface of the eyeball (except the cornea) and inside surface of the eyelids.
Conjunctival Hyperemia
Redness of the conjunctiva; associated with all types of conjunctivitis.
Conjunctival Sac
Pocket of conjunctiva between the upper eyelid and eyeball and lower eyelid and eyeball that permits the eyeball to rotate freely.
Conjunctivitis
An eye condition caused by the inflammation of the conjunctiva, or clear membrane covering the white part of the eye and lining of the eyelids. The eyes will often appear swollen and red while also feeling gritty. It can be bacterial, viral, or allergic and could be contagious. Call or see your doctor to treat conjunctivitis.
Contact Lens
Small disc worn on the cornea or sclera, providing visual correction of refractive errors.
Convergence
Moving both eyes towards each other to maintain single binocular vision of an approaching object.
Corectopia
Displacement of the pupil from its normal position.
Cornea
Transparent front of the eye covering the iris, pupil, and anterior chamber; provides the bulk of the eye's optical power.
Corneal Abrasion
Scraped area of the cornea accompanied by superficial tissue loss.
Corneal Apex
Central 3-5 mm where the cornea has the greatest curvature.
Corneal Edema
Hazy and swollen cornea.
Corneal Erosion
Loss of the outer layer of the cornea because it fails to adhere to the Bowman's membrane.
Corneal Hydrops
Corneal hydrops is a complication of advanced keratoconus and is characterized by sudden onset of severe corneal opacification because of edema. The edema occurs from a spontaneous break in Descemet's membrane (one of the 5 layers of the cornea) because of the weakened cornea, leading to a sudden and painful decrease in visual acuity.
Corneal Staining
Use of dye such as fluorescein to reveal corneal epithelial defects.
Corneal Transplant
Replacement of damaged or diseased cornea with donor corneal tissue.
Corticosteroid
Steroid used to treat inflammatory and allergic diseases.
Crystalline Lens
The eye's natural lens located directly behind the iris. It has the ability to change shape to focus light rays onto the retina.
Cup
Optic cup; depression in the center of the optic disc that normally occupies less than one-third of the dis diameter.
Cup-to-disc Ratio
Evaluates the progression of glaucoma by indicating the percentage of the disc occupied by the optic cup.
Cupped Disc
Abnormal enlargement of the optic cup, usually due to a long-term increase in intraocular pressure.
Cylinder Correction
Use of a lens that produces different refractive power in each meridian; used to correct astigmatism.
Cystoid Macular Edema
Retinal swelling and cyst formation ion the macular area, can result in temporary or permanent decrease in vision.
Dacryocystitis
Inflammation of the tear sac, often associated with poor tear drainage.
Depth Perception
Awareness of relative spatial location of objects; perception of nearness and farness.
Diabetic Macular Edema
The leaking of retinal blood vessels into the macula in patients with diabetes, causing the macula to swell, which can temporarily or permanently decrease central vision.
Diabetic Retinopathy
Progressive retinal changes that accompany diabetes mellitus; this can progress from background retinopathy to proliferative retinopathy, which includes abnormal new blood vessels and fibrous tissue development.
Diameter
The distance from one side of the lens to the other, usually around 13 to 15 millimeters that is associated with the size of your contact lenses.
Dilation
Widening of the pupil.
Diopter
Perception of two images from one object; double vision
Disc
Optic disc; ocular end of optic nerve
Dry Eye Syndrome
An eye condition that presents itself as itching, burning, and irritation of the eyes, is often called "dry eye syndrome". It is one of the most common problems treated by eye care professionals. It is usually caused by the breakdown (or deficiency) in the tears that lubricate the eyes. As we age, our bodies produce less oil to seal the eyes' watery layer. Hot, arid climates, air conditioning, certain medicines and irritants such as cigarette smoke can all increase dryness of the eye. Your eye care professional might prescribe "artificial tears" or other eye drops to help alleviate the problem.
Dyscoria
Distorted shape of pupil.
Epicanthal Fold
Vertical skin fold at each side of the nose; hides the caruncle; present in infants before nose bridge is developed.
Epiphora
Overflow of tears down the face caused by poor tear drainage, excessive tearing, or outward turning of the lower eyelid.
Erythema
Abnormal skin redness caused by capillary congestion under the skin.
Esotropia
Eye misalignment in which one eye turns inward while the other stays fixed straight ahead.
Evisceration
Procedure that removes the contents of the eyeball, leaving behind the sclera shell and, sometimes, the cornea; usually for reducing pain in a blind eye.
Exotropia
Eye misalignment in which one eye turns outward while the other stays fixed straight ahead.
Exposure Keratitis
Corneal irritation or inflammation caused by corneal drying due to incomplete closure of the eyelid.
External Diseases
Diseases that affect the cornea, sclera, conjunctiva, or eyelids.
Eye
Sense organ for sight.
Eyelash
One of the stiff hairs at the margin on the eyelid.
Eyelid
Structure covering the front of the eye that protects it, limits the light entering in, and distributes the tear film over the corneal structure.
Eyewall
The sclera and the cornea.
Farsightedness
Refractive error that allows the eye to see clearly at a distance, but close-up images are blurred; hyperopia
Femtosecond Laser
Short-pulse laser that is used to create corneal flaps in refractive surgery.
Flashes
Flashes are a visual sensation that can look like a camera flash going off or a lightning streak in your vision. Flashes occur because the vitreous or "jelly" is tugging on the retina. If the vitreous tugs too hard, it may cause a vision threatening event called a retinal tear or detachment. If you notice a sudden increase in the number of flashes you see, call your eye care professional.
Floaters and Spots
A generalized term used to describe small specks moving subtly but noticeably in your field of vision. A floater or a spot is likely a tiny clump of gel or cells in the vitreous — the clear, jelly-like fluid inside your eye. Aging, eye injury and breakdown of the vitreous are the main causes of floaters and spots. If you notice a sudden increase in the number you see, call your eye care professional.
Fluorescein
Colored dye that illuminates; used on the cornea to identify damage.
Focal Point
Position on the principal axis of a lens system where parallel light rays are brought to a point of focus.
Focal Point
Position on the principal axis of a lens system where parallel light rays are brought to a point of focus.
Follicles
Tiny elevations on the undersurface of the eyelids; associated with viral conjunctival inflammation.
Foreign Body Sensation
The feeling of something in the eye; can be caused by an actual foreign body in the eye or by various damage or conditions.
Fovea
A tiny spot in the center of the retina that contains only cone cells. This area is responsible for our sharpness of vision.
Fundus
Interior posterior surface of the eyeball which includes the retina, optic disc, macula, and posterior pole.
Gerontoxin
Degenerative change that produces a white ring-shaped deposit of fat near the peripheral edge of the cornea; typically in patients over 60.
Glare Test
Clinical test that determines the extent to which a bright light shined in the eye changes visual acuity; evaluates the degree of visual impairment caused by a cataract.
Glaucoma
A common cause of preventable vision loss that is due to damage to the optic nerve, the nerve that carries visual information from the eye to the brain. Treatable by prescription drugs or surgery.
Globe
The eyeball; a sensory organ that uses light to transmit visual information to the brain; 3 major layers in the globe include corneo-sclero, uvea, and retina.
Goblet Cell
Large mucous glands in the conjunctiva that secrete mucin, a component of precorneal tear film; can be damaged in Dry Eye sydrome.
Gonioscopy
Test that examines the anterior chamber angle structures through a special lens with a slit lamp.
Graves Disease
Symptoms of the eye that may result with excessive thyroid-related concentration, including eyelid retraction, eyelid lag, corneal drying, and optic nerve inflammation.
Halo
Hazy ring seen around lights; can be a sign of a refractive error or optical defect such as cataract.
Herpes Keratitis
Eye infection caused by the herpes simplex virus. Results in inflammation and ulcers.
Heterochromia of the Iris
Having a different color iris in each eye.
High(er) Index
A dense lens material that results in thinner, lightweight lenses than standard plastic. Index refers to index refraction which is the speed that light travels through the lens. Higher index lenses are available from 1.56 to 1.74 (the higher the number, the thinner the lens). They benefit people with stronger prescription eyeglasses.
Histamine
Chemical that creates an allergic or inflammatory response.
Hordeolum
Acute infection of oil glands of the eyelid; externally, also known as a stye; internally (in the meibomian glands), also known as a chalazion, if chronic.
Hyperemia
Clinical sign; increased blood flow; usually refers to eye redness due to increased blood flow to the conjunctival blood vessels.
Hyperopia
A condition where they eye is too short for its optical power causing distant objects to be seen clearly, yet objects close up are seen less clearly. Also commonly referred to as "farsighted."
Hypertropia
Functional defect in which one eye deviates upward while the other remains straight and fixates normally.
Hyphema
Clinical sign; blood in the anterior chamber, often following blunt trauma to the eyeball.
Hypotropia
Functional defect in which one eye deviates downward while the other remains straight and fixates normally.
Intraocular Lens
Lens that may be surgically implanted to replace the eye's natural lens.
Intraocular Pressure (IOP)
The pressure of fluid within the eye; elevated IOP is a treatable risk factor for glaucoma.
Iridectomy
Removal of a portion of iris tissue.
Iris
Pigmented tissue behind the cornea that gives the eye its color and allows light to enter the eye by controlling the size of the pupillary opening; part of the uveal (middle) layer of the eye.
Iritis
Inflammation of the iris, causing pain, tearing, blurring, small pupil, and red congested eye.
Isopia
Equal vision in both eyes.
Keratectomy
Surgical removal of corneal tissue.
Keratitis
Corneal inflammation; can be caused by a variety of infections, injuries, and unknown causes.
Keratoconjunctivitis Sicca
Corneal and conjunctival dryness due to deficient tear production; Dry Eye syndrome.
Keratoconus
– Keratoconus is a condition that causes progressive weakening, thinning and cone-like bulging of the cornea. This irregularity in the shape of the cornea causes light rays hitting the cornea to become out of focus and results in blurry and distorted vision that cannot be corrected by wearing glasses. Distorted vision from Keratoconus can be corrected by special gas permeable contact lenses. Corneal damage from Keratoconus is not reversible however its progression can be slowed down and even halted completely by a procedure called Collagen Cross-linking. In severe cases of keratoconus, transplantation of the cornea may be necessary.
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Keratolysis
Corneal melt; superficial corneal layers that "melt" away; often associated with severe inflammation, Dry Eye, or rheumatoid arthritis.
Keratoplasty
Surgical procedure on the cornea that usually refers to a corneal graft (replacing damaged corneal tissue with donor tissue).
Keratotomy
Any incision into the cornea (surgical procedure).
Lacrimal Gland
Almond-shaped gland located above the eyeball in the upper outer region that produces tears.
Lacrimation
Tear production; crying.
Laser
Acronym for Light Amplification by Stimulated Emission of Radiation; a high-energy light source that can cut, burn, or dissolve tissues for clinical procedures; used in many eye care procedures such as refractive surgery, treatment of diabetic retinopathy and macular degeneration, and removal of trabecular meshwork in glaucoma patients.
LASIK
LAser in Sltu Keratomileusis; refractive surgery in which the cornea is reshaped to change its optical power; corrects myopia, hyperopia, and astigmatism.
Legal Blindness
Visual Acuity of 20/200 or less, or visual field reduction to 20 degrees or less (in the better eye).
Lensectomy
Removal of the eye's natural lens.
Limbus
Area where the cornea joins the sclera and the bulbar conjunctiva attaches to the eyeball.
Lipiflow
– Lipiflow is a heat treatment for Meibomian Gland Dysfunction. It provides a warm and gentle heat to the eyelids while simultaneously applying a gentle massage. This combination effectively removes the blockages in the meibomian glands and allows them to secrete the clogged oil. After a session of LipiFLow treatment, the glands will be able to resume its natural production of oil for the tear film.
Low-tension Glaucoma
Also known as Normal-tension glaucoma; type of open-angle glaucoma in which a patient exhibits signs such as progressive disc cupping and visual field loss, but with normal intraocular pressure.
Macropsia
Distorted vision in which objects appear larger than normal.
Macula
The part of the retina responsible for the sharp, central vision needed to read or drive.
Macular Degeneration
A group of conditions that include a deterioration of the macula causing a loss of central vision needed for sharp, clear eyesight. It is a leading cause of vision loss and blindness in those 65 years of age and older. Macular Degeneration is also called AMD or ARMD (age-related macular degeneration).
Macular Edema
Swelling and cyst formation in the macula; can temporarily or permanently decrease vision.
Maculopathy
Abnormality of the macula.
Madarosis
Loss of eyelashes often caused by chronic blepharitis.
Magnification
Increased image size created through the use of optical devices.
Meibomian Gland
Oil gland in the eyelid tissue that secretes the outer portion of the tear film; prevents rapid tear evaporation and tear overflow.
Microbial Keratitis
Corneal infection from overuse of contact lenses; caused by microorganisms.
mm Hg
Millimeters of mercury; units used to measure intraocular pressure.
Moll Glands
Sweat glands near the eyelash follicles; infection can cause a stye.
Monocular
Referring to one eye.
Multi-Focal Lenses
Multi-focal lenses let you focus on two or more distances through the same lens (usually distance, intermediate, and near). Also known as Bifocals, Trifocals, and Multifocals.
Myopia
A condition cuased by an overpowered eye, which has too much optical power for its length, where distant objects appear less clearly and those objects up close are seen clearly. Also commonly referred to as "nearsighted."
Narrow-angle Glaucoma
Rise in intraocular pressure caused by narrow anterior chamber angles that prevent aqueous drainage.
Nasolacrimal Duct
Tear drainage channel from the lacrimal sac to the mucous membrane of the nose.
Nasolacrimal Duct Obstruction
Is a blocked tear duct that occurs when your nasal passageways cannot properly drain tear liquid from your eyes. You may have crusty, itchy, irritated or watery eyes. Sometimes, babies are born with blocked tear ducts.
NCLE
National Contact Lens Examiners are certified professionals in Optometry who fit and work with contact lenses.
NDC number
US National Drug Code; a standard code used to to identify FDA-approved drugs and biologicals.
Nearsightedness
Refractive error that allows the eye to see close-up objects clearly, but distance vision is blurred; myopia.
Neurotrophic Keratitis
Corneal inflammation resulting from trauma or damage to corneal nerves; leads to cornea anesthesia.
Night Blindness
Poor visual adaptation to the dark, resulting in reduced vision in low light; usually indicates defect in retinal rods.
Nyctalopia
Commonly called "night blindness," this is a condition that presents as impaired vision in dim light or darkness.
Nystagmus
A functional defect in which the patient displays involuntary oscillating eye movements that are faster in one direction than the other.
Ocular Biometry
Test that measures distance between various ocular structures (usually with A-scan or B-scan ultrasound instruments).
Ocular Hypertension
Elevated IOP, but with no evidence of optic disc or visual field changes; potential (but not definite) glaucoma suspect.
Ocular Surface
Disease Index© (OSDI©)
A valid and reliable instrument of 12 questions for measuring Dry Eye Disease and its effect on vision-related function.
OD
Right eye.
Open-angle Glaucoma
The most common type of glaucoma caused by the slowing of normal aqueous outflow from the eye; can result in gradual, irreversible vision loss.
Ophthalmologist
Doctor of medicine (MD) or doctor of osteopathic medicine (DO) specializing in diagnosis and treatment of eye diseases and disorders.
Ophthalmology
Medical specialty dealing with function and disease of the eye.
Ophthalmoscopy
Use of an ophthalmoscope to examine the internal structures of the eye.
Optic Nerve
The second cranial nerve that is the largest sensory nerve of the eye; carries sight information from the retina to the brain for processing.
Optic Neuropathy
Abnormality or degeneration of the optic nerve, not due to inflammation.
Optician
Vision care professional who makes and adjusts optical aids such as eyeglasses.
Optomap
Retinal imaging that captures more than 80% of your retina in one panoramic image that allows your Optometrist to provide you with the most comprehensive eye exam possible by detecting underlying eye diseases and monitor treatment for existing ocular diseases.
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Optometrist
Doctor of optometry (OD) who specializes in vision problems and treatments.
Optometry
Vision care specialty that deals with the detection and management of ocular disease.
Orbit
Socket; cranial cavity of the skull that contains the eyeball.
Orthokeratology
“Ortho-K” is a lens fitting procedure that uses specially designed rigid gas permeable (RGP) contact lenses to change the curvature of the cornea to temporarily improve the eye's ability to focus on objects. The lenses are worn at night to give clear vision during the day
OS
Left eye.
Outflow (aqueous)
Passage of aqueous fluid out of the eye through the anterior chamber angles.
Pachymetry
Test to measure corneal thickness
Palpebral Fascia
Fibrous membrane that forms a protective layer between the eyelid and the bony orbit (socket)
Paraoptometric
Certified allied health professional in optometry; three levels are certified by CPO®: CPOA®, and CPOT®
Perennial Allergies
Also known as year-round allergies, these are usually due to indoor allergies such as dust mites or mold
Periocular
Area surrounding the eyeball
Peripheral Vision
Side vision, created by stimuli falling on retinal areas that are far from the macula
Phacoemulsification
Surgical procedure that uses ultrasound vibration to break up a cataract, making it easy to suction out of the eye
Phakic
Refers to an eye that has its natural lens
Photochromic Lenses
Refers to lenses that automatically change from clear to dark in the presence of ultraviolet (UV) radiation.
Photophobia
Abnormal sensitivity to light; associated with discomfort and excessive tearing; often due to iritis or keratitis
Photopsia
Sensation of light or flashes from mechanical or electrical irritation of the retina (not from a light stimulus)
Photorefractive Keratectomy (PRK)
Refractive surgery that reshapes the corneal curvature with a laser after the surface of the cornea has been removed
Pink Eye
Conjunctivitis; inflammation of the conjunctiva that is usually viral in origin; symptoms include discharge, grittiness, redness, and swelling
Plastic 1.50
This is a lens material often used for minor prescriptions. Very few lenses are made from glass today, since glass is heavier, thicker, and can shatter. Also referred to as standard index or by the brand name CR-39.
Polarized Lenses
This type of lens includes an invisible “polarized” filter that helps to cut down on blinding glare from reflective surfaces like water and snow for increased visual acuity (sharpness) in bright light conditions.
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Pollen
Microspores of seed plants that can induce allergic or hypersensitivity reactions in some people
Polycarbonate Lenses
A lens material that is thinner, lighter, and more impact resistant than standard plastic. Polycarbonate lenses are the standard for children’s eyewear.
Posterior Capsular Opacification
After cataract surgery, the rear lens capsule can cloud over; needs removal to improve vision
Posterior Chamber
Space between the back of the iris and the front of the vitreous
Presbyopia
Condition in which the aging crystalline lens (at around age 40) becomes less able to change shape to focus light at all distances, especially near vision. Presbyopia can be corrected with reading glasses, bi-focal glasses, or progressive lenses. Additional symptoms include eyestrain, headaches, and squinting.
Primary Open-angle Glaucoma
The most common type of glaucoma caused by the slowing of normal aqueous outflow from the eye; can result in gradual vision loss
Prism
Prism correction is used in eyeglasses for some people with diplopia, or double vision. The prism helps align the two images, so that only one image is seen.
PRN
As needed (as medication dosing)
Progressives
Bi-focal or multi-focal lenses with no visible lines where the lens power gradually changes from distance to near. Also called PALs (Progressive Addition Lenses).
Pruritus
Itching
Pseudoexfoliation
Unknown deposits appearing on the lens surfaces and other ocular structures; often associated with high intraocular pressure
Pterygium
A raised growth on the eye that is most often directly related to over-exposure to the sun. Dry, dusty conditions may also contribute to development of these growths. Protecting your eyes from UV radiation is a critical preventive measure.
Ptosis
Sagging upper eyelid
Puff Tonometer
Device that measures intraocular pressure by blowing a puff of air against the cornea to flatten it
Punctal Plug
Plastic plug inserted into the punctum to prevent tear drainage, preserving tears to keep the eye moist
Punctate Keratitis
Corneal disease characterized by small corneal lesions of unknown origin
Pupil
Black circular opening in the center of the iris that varies in size to regulate the amount of light that enters the eye
Pupillary Distance
Pupillary distance (PD) is the distance between the pupils of your two eyes. It is an essential measurement when buying a new pair of prescription eyewear. For greatest comfort and clarity, these measurements should be taken by the optician involved in manufacturing the spectacles.
Pupillometer
An instrument used to measure the distance between pupils. This measurement is used to position the eyeglass prescription correctly in front of the eye.
QD
Once daily
QID
Four times daily
Refraction
Test to determine an eye’s refractive error and the best corrective lenses to be prescribed.
Refractive Error
Optical defect in an unaccommodating eye; correctible with surgery, eyeglasses, or contact lenses
Retina
Light-sensitive tissue in the eye that converts images into electrical impulses that are sent to the brain via the optic nerve to interpret as vision. Consists of layers that include rods and cones.
Retinal Detachment
Separation of the retina from the underlying pigment epithelium; usually caused by a retinal tear that leaks fluid from the vitreous and separates the retina
Retinal Hole
Retinal holes and tears are small breaks in the retina. Usually holes do not mean you will have serious vision problems right away. However, retinal holes and tears may cause problems if they allow fluid to seep behind the retina and cause the retinal layers separate from each other or detach from layers underneath.
Retinal Vein Occlusion
Blockage of blood flow through the central retinal vein, causing a decrease in vision
Retinitis
Inflammation of the retina
Retinoblastoma
Malignant tumor that develops from retinal visual cells
Retinopathy
Any noninflammatory degenerative disease of the retina
Retinoscopy
Test that measures the eye’s refractive error
Rigid Gas Permeable “RGP” Lenses
Gas permeable contact lenses are rigid lenses made of durable plastics that allow oxygen to pass through the lens.
Rods and Cones
These are cells inside the eye used by the retina to process light. Rods are used for low light levels (night vision), cones are used for sharp visual acuity and color perception.
Schirmer Test
Measures tear production with filter paper strips
Schlemm’s Canal
Channel in the corneo-scleral junction that carries aqueous fluid from the anterior chamber to the bloodstream
Sclera
Opaque protective outer layer of the eye (“the white”) that connects to the cornea and the sheath of the optic nerve
Scleral Lenses
Scleral lenses are large-diameter gas permeable contact lenses that vault over the cornea (the clear front of the eye) and rest over the sclera (the white of the eye). The scleral lens provides a smooth optical surface that works to correct vision problems caused by keratoconus and other irregular cornea problems.
Scleritis
Inflammation of the sclera, often painful
Seasonal Allergies
Allergies, such as hay fever, that are seasonal in nature (eg, springtime or fall)
Single-Vision
Types of lenses that correct one vision problem, like near or far-sightedness.
Sjögren Syndrome
Chronic autoimmune disease often characterized by dry eyes, dry mouth, and arthritis
Slit Lamp
Microscope used to examine the eye; shows the cornea, lens, and clear fluids and membranes in layered detail
SLT Surgery
Surgical procedure in which a laser is used on the trabecular meshwork to increase aqueous outflow, reducing intraocular pressure
Snellen Chart
Lettered chart for measuring visual acuity; usually tested at 20 feet (hence, 20/20 vision)
Snellen Chart
This is the commonly seen eye chart often topped by a large letter “E” used in eye examinations. This measures your eye’s visual acuity, or the ability to see sharp detail clearly.
Somnolence
Sleepiness
Sphere
Sphere indicates the amount of lens power prescribed to correct nearsightedness or farsightedness.
Strabismus
Sometimes called “crossed eyes” in young children, this condition is the lack of coordination between the eyes, such as one or both eyes turning in, out, up or down.
Tachyphylaxis
Rapid decrease in response to a given dose of a drug after repetitive administration.
Tarsal Gland
Oil gland within the eyelid tissue; secretes the outer portion of the tear film to prevent tear evaporation and overflow
Tear Breakup Time
Tests the time between a blink and the development of a dry spot on the ocular surface; less than 10 seconds is abnormal.
Tear Duct
Tear drainage channel from the lacrimal sac to the mucous membrane of the nose.
Tears
Fluid secreted by the lacrimal glands to keep the conjunctiva and cornea moist.
Temporal Pallor
Loss of pinkish tone in the optic disc; usually indicates optic nerve damage.
TID
Three times daily.
Tonometer
Instrument that measures intraocular pressure; each type of tonometer measures pressure through slightly different means.
Toric Lens
An optical device with a cylindrical component to correct astigmatism.
Trabecular Meshwork
Structure inside the eye at the iris-scleral junction of the anterior chamber angle that filters aqueous fluid and controls its exit from the eye through Schlemm’s canal.
Trabeculectomy
Surgical procedure to remove part of the trabecular meshwork to increase the outflow of aqueous fluid to treat elevated intraocular pressure.
Trabeculoplasty
Surgical procedure that uses a laser to burn part of the trabecular meshwork to increase outflow of aqueous fluid to treat elevated intraocular pressure.
Trachoma
Severe, chronic, and contagious infection of the eyelid and cornea caused by a virus; the leading cause of blindness in the world.
Trichiasis
A condition caused by misdirected or abnormally positioned eyelashes. Trichiasis, sometimes caused by entropion causes discomfort and irritation to the eye, and can lead to permanent damage to the cornea and vision loss.
Trifocal
Optical device that incorporates lenses of 3 different powers.
Triplopia
Ocular defect that causes images to appear in triplicate; often caused by an early cataract
Ultraviolet Light
Light with wavelengths between 250 and 400 nanometers; invisible to the naked eye.
Ultraviolet Radiation (UVR)
Commonly referred to as “UV Rays”, these are light waves that consist of both UVA and UVB rays from the sun. Without proper protection, chronic exposure to UV rays can lead to various eye conditions and damage.
UV Protection
Relates to a lens’ ability to filter out harmful rays of the sun. It is recommended that glasses block 100% of both UVA and UVB rays to minimize eye damage from the sun’s rays.
Uvea
Pigmented vascular layers of the eye (iris, ciliary body, and choroid) that contain most of the eye’s blood vessels.
Uveitis
Inflammation of any of the structures of the uvea (iris, ciliary body, or choroid).
Vision
Ability of the eye to receive and transmit light images to the brain, where they are interpreted; the ability to see.
Visual Acuity
Assessment of the eye’s ability to distinguish object details and shape – numerically expressed as 20/20, 20/70, etc.
Visual Field
The full area visible to the eye when fixated straight ahead; measured in degrees.
Vitrectomy
Surgical removal of the vitreous.
Vitreous
Transparent gelatinous mass that fills the back two-thirds of the eyeball between the lens and retina.
Year-round Allergies
Also known as perennial allergies, these are usually due to indoor allergies such as dust mites or mold.
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