Eye Terminology
A-C
Ablate
To remove by erosion, evaporation or vaporization.
Accommodation
The eye’s ability to change its focus from distance to near objects, a process achieved when the lens changes shape.
Accommodative Intraocular Lens
An intraocular lens implant that’s designed to function similar to the natural eye. After surgical insertion the eye is intended to focus on near, intermediate and far objects. The purpose of this lens is to lessen or eliminate dependence on glasses.
Amblyopia (Lazy Eye)
A disorder of the coordination between the eye and the brain, usually beginning in childhood that causes the body to prefer one eye over the other, leading to unequal vision.
Aniridia
A congenital condition in which the iris is absent or partially absent. May also result from trauma to the eye.
Anterior Chamber
The space in front of the iris and behind the cornea.
Aqueous Humor
Clear, watery fluid that flows between the lens and cornea and nourishes them.
Astigmatism
A condition that occurs when an uneven curvature of the eye causes light to be refracted (bent) unevenly, resulting in distorted vision.
D-F
Diabetic Retinopathy
A complication of diabetes in which the blood vessels in the eye become diseased, and may cause vision loss.
Dilation
A process by which the pupil is temporarily enlarged with special eye drops to allow examination of the interior of the eye.
Diopter
A unit of measurement used to describe the degree of refractive error with respect to nearsightedness, farsightedness and astigmatism.
Drusen
Small, yellow or white deposits in the retina or optic nerve head.
Dry Eye Syndrome
A condition caused by the reduction in quality and quantity of tears.
Ectropion
A condition that occurs when the lower eyelid turns outward, which may result in dry eye symptoms and excessive tearing.
Endothelium
A thin layer of cells lining the undersurface of the cornea that pump fluid from the cornea, keeping it clear.
Entropion
A condition in which the lower eyelid turns inward, causing irritation and may lead to serious infection.
Flashes and Floaters
A condition that occurs when the back of the eye, filled when a jelly-like substance (vitreous gel), becomes increasingly more liquid-like in nature, causing small particles, called floaters, to become visually evident. Flashes originate from the tugging on the retina as the vitreous gel liquefies.
Fluorescein Angiography
A test to examine blood vessels in the retina, choroid and iris in which a special dye is injected into a vein in the arm and photographic images are created as the dye passes through blood vessels in the eye.
Focal Point/Focus
The refraction of light rays by the cornea and the inner lens to a focal point on the retina in a precise, natural manner that produces sharp, clear and colorful images.
Fovea
The central part of the macula that provides the sharpest vision.
Fundus
The interior lining of the eye, including the retina, optic disc and macula, which can be seen during an eye examination by looking through the pupil.
G-I
Glaucoma
A vision-threatening disease that can cause optic nerve damage, most often from high pressure caused by poor drainage of a fluid (aqueous humor) which supplies nutrients to the cornea and lens.
Herpes Zoster (Shingles)
An infection, produced by the same virus that causes chicken pox that may reactivate on the skin or in the eye, causing inflammation and scarring.Hordeolum (stye): A red, painful, swollen, cyst-like bump of the eyelid caused by a localized inflammatory process.
Hyperopia (Farsightedness)
A condition that occurs when the cornea is relatively underpowered and/or the eye is too short, thus causing light to be focused behind the retina, leading to blurred vision.
IOL
Intraocular lens implant. An artificial lens that is implanted inside the eye.
Intraocular Pressure
Pressure of the fluid inside the eye, which varies among individuals.
Iris
The colored ring of tissue, suspended behind the cornea and immediately in front of the lens, which regulates the amount of light entering the eye by adjusting the size of the pupil.
Iritis
An inflammation of the colored part of the eye, or iris, resulting in an eye that is red, painful and sensitive to light. Also called uveitis.
J-L
Keratoconus
This condition arises when the middle of the cornea thins and gradually bulges outward, becoming cone shaped, producing moderate to severe astigmatism and blurriness.
Keratometer
A sophisticated instrument that measures the frontal curvature, or steepness of the cornea, comparing high and low points to determine if a refractive problem exists.
Lacrimal Gland
The small, almond-shaped structure, located above the outer cornea of the eye, which produces tears.
Laser
The acronym for Light Amplification by Stimulated Emission of Radiation, which is used in vision correction procedures and refractive surgery.
LASIK
The acronym for Laser In Situ Keratomileusis, which is a revolutionary vision-correction procedure for the treatment of nearsightedness, farsightedness and astigmatism.
Legal Blindness
Visual acuity of 20/200 or worse in the better eye with corrective lenses, or a visual field restriction of less than 15 degrees.
Lens
The transparent, double convex structure suspended between aqueous and vitreous humor, which helps to focus light on the retina.
Lensectomy
The surgical removal of the eye’s natural lens. Performed for the treatment of cataracts or as a means of treating a severe refractive error.
Limbus
The junction of the outer perimeter of the cornea with the sclera.
Low Vision
Visual loss, which cannot be corrected with conventional glasses or contact lenses. May interfere with daily living activities and can be treated by a low vision specialist or center, e.g. Center for Visually Impaired.
M-O
Macula
Macula Degeneration
A condition caused by the breakdown of the macula, the center part of the retina, resulting in gray, hazy or blocked vision.
Microkeratome
A sophisticated surgical instrument that is used in LASIK and refractive surgery to sculpt micro-thin layers of corneal tissue.
Micron
A unit of length equal to one-thousandth of a millimeter.
Monovision:
A refractive correction, achieved with lenses or LASIK, which uses one eye for distance and one eye for near vision.
Myopia (Nearsightedness)
A condition that results from the visual image being focused in front of the retina. It occurs if the cornea is relatively too steep and/or the eye is too long, and results in blurred vision for distant sight.
Nevus
A benign, pigmented lesion that can occur in or around the eye.
Nomogram
A compilation of data that serves to predict a result. Nomograms were commonly used in refractive surgery before custom wavefront treatments became available.
Ophthalmologist
A physician who has received advanced training to treat diseases of the eye by medical and surgical approaches.
Optic Cup
The cup-like area in the center of the optic disc.
Optic Disc/Optic Nerve Head
The circular area (disc) where the optic nerve connects with the retina.
Optic Nerve
The bundle of 1.0 – 1.5 million nerve fibers that carries visual messages from the retina to the brain.
Optical Zone
The central area of the cornea that performs a majority of the refractive functions of the eye.
Optician
A licensed specialist trained in the fitting, adjustment, and dispensing of eyeglasses, sunglasses, and contact lenses.
Optometrist
A professionally licensed eye specialist who prescribes eyewear, contact lenses, low vision aids, and vision therapy for adults and children. An optometrist may also treat non-surgical eye diseases, such as infections, allergic conditions and glaucoma.
P-R
Peripheral Vision
Non- central vision; includes sight to the sides and up/down.
Phoropter
An instrument used to determine the degree of myopia, hyperopia or astigmatism present in the eye.
Pinguecula
A slightly raised, yellowish thickening of the white part of the eye (conjunctiva) adjacent to the cornea, typically caused by repeated sun and wind exposure.
Phakic
Refers to an eye that possesses its natural lens.
Posterior Chamber
The space between the back of the iris and the front of the lens. The most common location for intraocular lens placement.
Presbyopia
The inability to focus at near objects without glasses. Caused by hardening of the lens and loss of focusing flexibility.
Pterygium
A wedge-shaped growth on the cornea that can cause irregular astigmatism and obscure vision. Generally caused by chronic sun and wind exposure.
Ptosis
Drooping of the upper eyelid due to muscular weakness, older age, trauma, neurological disorder, or lid manipulation, such as contact lens wear.
Pupil
The adjustable opening at the center of the iris that allows varying amounts of light to enter the eye.
Radial Keratotomy (RK)
A surgical procedure to correct mild to moderate cases of nearsightedness and astigmatism. Involves placement of patterned, radial incisions in the peripheral cornea to change corneal shape.
Refraction
A vision analysis to determine one’s optimal glasses prescription. The information is used to obtain glasses and is also the basis for contact lenses fitting.
Retina
The light-sensitive layer of tissue that lines the back of the eye and sends visual messages through the optic nerve to the brain.
Retinal Detachment
A potentially vision-threatening condition that occurs when the retina separates from the supporting structures in the rear of the eye.
Retinal Pigment Epithelium (RPE)
A pigmented cell layer located beneath the retina. An important barrier and key structure in the formation of macular degeneration.
Rods and Rod Cells
Specialized light-sensitive cells (photoreceptors) that provide sight in low-light settings and are responsible for the bulk of one’s peripheral vision.
S-U
Schlemm’s Canal
The passageway in which the aqueous fluid leaves the eye.
Sclera
The tough, white outer layer of the eye that provides support and protects the eye.
Strabismus
Misaligned eyes; the abnormal eye may deviate in any direction.
Stroma
The strongest and thickest layer of the cornea. The area treated by LASIK surgery.
Subconjunctival Hemorrhage
A condition that occurs when a blood vessel of the white part of the eye (conjunctiva) breaks and bleeds, resulting in a reddened eye.
Suture
A surgical strand used to close an incision.
Systemic Disease
A disease that affects the body in more than one specific area.
Thermokeratoplasty (CK)
A refractive procedure that uses a laser to heat and shrink tissues in the peripheral cornea. Intended to alter corneal shape and correct cases of farsightedness and/or astigmatism.
Tonometry
The means to determine the eye’s intraocular fluid pressure.
Topography
An advanced test that maps the curvature of the cornea, and is used to evaluate forms of astigmatism.
Trabecular Meshwork
The site for drainage of aqueous humor, and is analyzed closely in glaucoma. This region may be treated with a laser as a means to lower intraocular pressure.
Ultrasonic Pachymeter/Pachymeter
An instrument that measures corneal thickness.
Uvea, Uveal Tract
The middle coat of the eye, consisting of the choroids in the rear and the ciliary body and iris in front of the eye.
V-Z
Visual Acuity
The ability to distinguish details and shapes of objects.
Visual Field
The entire area that can be seen with the eye, including peripheral vision.
Vitreous
The transparent, colorless mass of gel that lies behind the lens and in front of the retina. Occupies four fifths of the volume of the eye.
Wavefront
A three dimensional system that evaluates the path of light within the eye. Tracks and records visual abnormalities beyond simple nearsightedness, farsightedness, and astigmatism.
Wavescan Systems
A component of the LASIK procedure that uses wavefront technology to record an individualized and precise analysis of the eye. The information is integral in creating a custom and personalized approach to LASIK laser vision correction.
Y.A.G (YAG) Capsulotomy
A quick, painless laser procedure to treat clouding of the posterior capsule. This treatment allows light to more effectively reach the retina.
Zonules
Delicate fibers that hold the lens suspended in position and enable it to change shape during accommodation.