glossary

Glossary of Eye Care Terms

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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
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Abduction – Eye rotation away from the midline


Aberration – Blurred or distorted image quality resulting from the physical properties of an optical device (ie, lens)


Accommodation – The eye’s increase in optical power in order to maintain image clarity as objects are moved closer


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

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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


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


Blepharoplasty – Any plastic surgery of the eyelids; often cosmetic


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 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.

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Capsulotomy – Incision to remove part 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


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


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.


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 – Inflammation of the conjunctiva; usually viral and can be contagious


Contact Lens – Small disc worn on the cornea or sclera, providing visual correction of refractive errors


Convergence – Moving both eyes toward 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 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 disc 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 in the macular area, can result in temporary or permanent decrease in vision

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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


Dilation – Widening of the pupil


Diopter – Diopter strength refers to the refractive power of a lens.


Diplopia – Perception of two images from one object; double vision


Disc – Optic disc; ocular end of the 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

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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 surface


Eyewall – The sclera and the cornea

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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


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


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

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