glossary

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

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.

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

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

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