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Glossary items starting with:

Glossary items starting with: A


(uh-kah-muh-DAY-shun). The ability of the eye and specifically crystalline lens inside the eye to focus on near objects.

Add Power

This is the amount of power you would need in a bifocal, if any. As you get older you lose the ability to focus at near. You may need added power at the bottom rim of your lenses to help you see more clearly at near with your existing eyeglass prescription. Whether you are near sighted, far sighted, or have never worn eyeglasses at all, you may need to wear a bifocal lens or reading glasses at some point in your life.

After-cataract (secondary cataract)

After-cataracts are a type of cataracts that form after surgery for other eye problems, such as glaucoma. After-cataracts also can develop in people who have other health problems, such as diabetes. They are sometimes linked to steroid use.

Amsler grid

(AM-slur). A small grid that tests for retinal disorders, and is sometimes given to macular degeneration patients to take home in order to monitor any changes in their condition.

Angle, anterior chamber angle

The area in the front of the eye where fluid from inside the eye drains out.


(ay-FAY-kee-uh). Once a patient has had a cataract removed, the eye is considered "aphakic". If an intra-ocular lens is put in, which is typical, the eye is considered "pseudo-phakic".


(AY-kwee-us). The liquid that fills the front chamber of the eye to keep the eye round and the cornea nourished.


A measurement of the length of the eye taken before cataract surgery to properly determine the power of the lens implant.


(as-then-OH-pee-uh). Any type of uncomfortable feeling in the eye, or eyestrain.


(uh-STIG-muh-tiz-um). An irregular shape to the cornea causes this common refractive error that can usually be corrected with glasses or contact lenses.


This is the degree the cylindrical correction sits at for optimal vision. You will only have this measurement if you have cylindrical correction.

Glossary items starting with: B


Glasses that correct for blurred vision far away and up close.

Binocular vision

The two eyes working together to see one image without eyestrain.


(blef-uh-RI-tus). A common bacterial infection of the eyelids and eyelashes, requiring special hygiene measures and at times prescription medication.

Blind spot

An area in the field of vision where objects cannot be seen. Everyone has a normal "physiologic" blind spot, but other blind spots from strokes, glaucoma or other diseases are not normal.


A 2 dimensional ultrasound view of the inside of the eye, useful in looking beyond a cloudy cornea or hemorrhage in the eye to determine the health of the retina.

Glossary items starting with: C


A clouding of the normally clear human lens inside the eye, causing vision to be blurred.

Cataract extraction

A surgical procedure done with ultrasound that removes the cloudy lens to restore vision.

Central retinal artery

The main artery that supplies blood to the eye.

Central retinal vein

The main vein that circulates used blood from the eye back to the heart.

Central vision

Straight ahead vision, when you look directly at someone or at a book to read.


(kuh-LAY-zee-un). A stye on the eyelid which is the result of a blocked tear duct or infection.


(KOR-oyd). A stye on the eyelid which is the result of a blocked tear duct or infection.

Color blindness

The lack of ability to distinguish colors, which can be inherited or acquired from a retinal disease.


A type of retinal nerve cell that is responsible for central vision and color vision.


(kahn-junk-TI-vuh). The clear outer membrane covering the eye.


(kun-junk-tih-VI-tis). Sometimes referred to as "pink eye", an infection of the outer layer of the eye that can be caused by a bacterial or viral infection.


(con-VER-genc-es). The ability of the eyes to move in toward each other, as when one is reading or looking at a near target.


(KOR-nee-uh). The clear front covering of the eye, and the first surface where light is focused onto the retina.


See esotropia.

Crystalline lens

The clear human lens inside the eye, that along with the cornea, focuses light onto the retina to create a clear image.

Cylindrical Correction

This part of the prescription is used to correct astigmatism. Astigmatism is a condition that is caused when the shape of the front of the eye is football like instead of round. Therefore, the light passing through the eye is distorted and causes certain degrees of blurriness. By adding this correction to the eyeglasses you maximize clarity. This is the second set of numbers you will find in a prescription. Usually, the "cylindrical" component is "fine tuning".

Glossary items starting with: D

Diabetic retinopathy

(ret-in-AHP-uh-thee). Hemorrhages and abnormal blood vessels seen in the retina of diabetics, especially those whose disease is not controlled well.

Dilated pupil

A large pupil usually created by pharmacologic agents to allow a better look inside the eye.

Diopter (D)

(di-AHP-tur). A unit of measurement that describes the refractive power of a lens


Double vision, or seeing two or more objects when there is only one.


(DRU-zin). Small yellow or white deposits in the retina frequently associated with macular degeneration.

Dry eye syndrome

A lack of tears produced by the eye's lacrimal gland, thought to result from inflammation. This syndrome often leads to discomfort, specifically stinging, burning and a scratchy feeling.

Glossary items starting with: E


(ek-TROH-pee-un). The lower eyelid can lose its elasticity, causing it to turn outward, which sometimes can result in tear drainage problems and excessive tearing.


(em-uh-TROH-pee-uh). The refractive condition whereby light is focused perfectly on the retina, and the person sees 20/20 without any form of visual correction.


(en-TROH-pee-un). The lower eyelid turns inward, often resulting in eyelashes contacting the front of the eye with resultant irritation.


(ee-soh-TROH-pee-uh). An inward turning of the eye, commonly known as "crossed eyes."

Excimer laser

(EKS-ih-mur). An ultraviolet laser that removes human tissue precisely and without heat, thereby shaping the eye to reduce refractive errors such as reducing nearsightedness (LASIK or PRK.

Excimer laser

(EKS-ih-mur). An ultraviolet laser that removes human tissue precisely and without heat, thereby shaping the eye to reduce refractive errors such as reducing nearsightedness (LASIK or PRK.


(eks-oh-TROH-pee-uh). An outward turning of the eye, commonly known as "wall-eye."

Extraocular muscles

(eks-truh-AHK-yu-lur). The muscles that control eye movements, such as when one looks up, down or to the left or right.


The thin membrane of skin that is designed to protect the eye and keep it from drying out.

Glossary items starting with: F


See hyperopia.


See hyperopia.

Fluorescein Angiography

(FLOR-uh-seen an-jee-AH-gruh-fee). A dye is injected into the vein and high speed photographs are taken to look at the blood flow in the retina, meant to detect leakage of abnormal blood vessels such as in diabetes or macular degeneration.


(FOH-vee-uh). The very central part of the retina, used for fine focus distance and near vision.


The back of the eye, including the optic nerve and retina.

Glossary items starting with: G


(glaw-KOH-muh). A progressive disease of the optic nerve, often but not necessarily associated with high intraocular pressure, leading to slow deterioration of side (peripheral) vision. If there is a family history of glaucoma, other family members have up to a ten fold chance of developing the disease and should be checked yearly.


(goh-nee-AHS-koh-pee). A technique to look at the angle, the area of the eye where fluid drains out, which can be abnormal in people with glaucoma.

Glossary items starting with: H


(hi-pur-OH-pee-uh). Also known as far-sightedness, where distant objects are seen more clearly that print/objects up close.


(hi-FEE-muh). A hemorrhage inside the eye, often resulting from blunt trauma.

Glossary items starting with: I

IOL (intraocular lens)

An artificial lens, typically made of silicone or acrylic material, that is implanted in the eye at the time of cataract surgery to replace the cloudy human lens that is removed.


The colored part of the eye, which constricts or dilates depending on lighting conditions.

Glossary items starting with: K


(kehr-uh-toh-KOH-nus). A condition that causes the cornea to warp or bulge, leading to a large degree of astigmatism which requires treatment with either a rigid contact lens or a corneal transplant procedure.


(kehr-uh-TAH-mih-tree). A measurement of the curvature of the cornea.

Glossary items starting with: L

Lacrimal gland

The gland behind the upper eyelid that produces tears.


A powerful beam of light that is used in a variety of forms of surgery to remove or vaporize tissue.


(LAY-sik). Stands for "Laser Assisted In Situ Keratomileusis" which involves cutting a flap on the cornea, lifting it, and reshaping the cornea below with an excimer laser to reduce nearsighted or farsightedness, then replacing the flap.

Legal blindness

Typically defined in the U.S. as visual acuity (with glasses) worse than 20/200 in the better seeing eye, or in combination with significant peripheral vision loss.

Lens, crystalline lens

The lens inside the eye that, along with the cornea, bends (refracts) light onto the retina in order to create a sharp focus, allowing us to see clearly.

Low vision

The optometric specialty that involves helping those who are legally blind to use their remaining vision using strong magnifiers, telescopes, and daily living aids.

Low vision

The optometric specialty that involves helping those who are legally blind to use their remaining vision using strong magnifiers, telescopes, and daily living aids.

Glossary items starting with: M


The very sensitive central part of the retina responsible for fine focus vision and the perception of colors.


(mi-OH-pee-uh). Also known as nearsightedness, where objects up close are seen more clearly than distant objects.

Glossary items starting with: N


See myopia


(nee-oh-VAS-kyu-lur-ih-ZAY-shun). The formation of abnormal blood vessels, as seen in poorly controlled diabetes, which can lead to hemorrhages and retinal detachment.


(ni-STAG-mus). Rapid involuntary eye movements that may be the result of poor vision, or a neurological condition.

Glossary items starting with: O


(ahf-thal-MAH-loh-jist). An eye doctor who specializes in the diagnosis and treatment of eye diseases and surgery of the eye.


(ahf-THAL-muh-skohp). A lighted instrument used to examine the back of the eye, specifically the optic nerve and retina, to rule out conditions such as retinal detachment, diabetes, glaucoma, etc.

Optic disc

The point where the optic nerve enters the retina; not sensitive to light.

Optic nerve

The main nerve of the eye which carries visual information from the retina to the visual interpretation centers of the brain.


(ahp-TISH-un). A professional who specializes in making and fitting eye glasses.


(ahp-TAHM-uh-trist). An eye doctor who specializes in primary care of the eye, including correction of the visual system and the diagnosis and treatment of eye diseases.


Eye exercises designed to strengthen eye muscles and improve the way the eyes work together and focus.

Glossary items starting with: P


Covering an amblyopic patient's preferred eye, to improve vision in the other eye.


(puh-RIM-ih-tree). The measurement of the peripheral or side vision, often done with an automated computerized instrument.


(fay-koh-ee-mul-sih-fih-KAY-shun). An ultrasound technique used to break up the cloudy lens (cataract) inside the eye, allowing for a smaller incision.


(foh-toh-FOH-bee-uh). Sensitivity to light or glare.


(pin-GWEK-yu-luh). A growth on the outside of the eye, typically in the inner or outer corner, thought to be related to long term exposure to ultraviolet sunlight.

Pink eye

See conjunctivitis.


(prez-bee-OH-pee-uh). A condition that commonly develops after age 40, resulting from aging changes to the human lens and a lack of ability to focus up close requiring reading glasses.


Stands for "Photo Refractive Keratectomy," a procedure to reduce or eliminate nearsightedness by scraping the outer layer of the cornea and using an excimer laser to shape the eye.

Progressive Addition Lens (PAL)

Invisible bifocals that focus light at a variety of intermediate and near distances.

Proliterative retinopathy


(tur-IH-jee-um). A vascular growth on the outside of the eye, typically in the inner or outer corner, thought to be related to long term exposure to ultraviolet sunlight that can grow onto the cornea and affect vision.


(TOH-sis). A droopy upper eyelid.


The hole in the center of the iris that light is directed through onto the retina.

Glossary items starting with: R

Radial keratotomy (RK)

(keh-ruh-TAH-tuh-mee). A surgical procedure, popular in the 1970's and 80's, that used eight spoke-like incisions to induce flattening of the cornea and correct nearsightedness. RK has been replaced by LASIK and PRK.


The measurement of the visual system to determine the appropriate eyeglass or contact lens prescription.

Refractive error

The amount of nearsightedness, farsightedness or astigmatism that an individual has.


The inner lining of the eye, consisting of sensitive nerve cells that receive light images and converts them to electrical impulses that are sent the brain by way of the optic nerve.

Retinal detachment

A separation of the retina from the layers behind it, usually resulting from injury or seen in patients who are highly nearsighted. A retinal detachment can be surgically repaired but the amount of vision recovered depends on the extent of the detachment and how quickly it is diagnosed.


(RET-in-oh-skohp). An instrument used to determine the refractive error of the eye by shining a light in the eye and observing the reflected light images.


A type of retinal nerve cell responsible for night vision and peripheral vision.

Glossary items starting with: S

Schlemm's canal

(shlemz). The drainage channel where fluid exits the eye.


(SKLEH-ruh). The white protective outer coating of the eye.

Secondary cataract

Slit lamp

Also called a biomicroscope, used to magnify structures in the front and back of the eye to examine various structures and diagnose abnormal conditions.

Snellen chart

A vision chart that is read to determine one's visual acuity, or clarity of vision.

Spherical Correction

This measures the amount of correction that a person needs to see clearly at near of distance. This number can stand alone as a prescription or be combined with another set of numbers to complete a prescription. This number is always the first set of numbers in the prescription.


(struh-BIZ-mus). A misalignment of the eyes, often leading to double vision.

Sty, stye

Glossary items starting with: T


(tuh-NAH-mih-tree). The measurement of the pressure inside the eye, often related to glaucoma.

Trabecular meshwork

(truh-BEK-yu-lur). The drainage channel in the front of the eye, and the area that is lasered in glaucoma that does not respond to medication.


(TRI-foh-kul). A segmented lens for up close, with one section for intermediate (computer) range and another for reading vision.


The smallest line of the eye chart that someone with perfect vision can see.

Glossary items starting with: U

Uvea, uveal tract

(YU-vee-uh). The middle layer of the eye, sandwiched between the retina and choroid, that supplies the eye with nutrients via the blood vessel system.

Glossary items starting with: V

Visual acuity

The level of clarity of vision.

Visual field

The total area that can be seen both straight ahead and to the side.


(VlT-ree-us), vitreous humor. The gel like substance that fills the back chamber of the eye, helping keep the eye round.

Vitreous detachment

A separation of the gel like vitreous from the retina, in some cases leading to a retinal tear or detachment.