Glossary of Vision Terms

GLOSSARY OF VISION TERMS


Amblyopia: A condition resulting in the functional non-use of one eye due to a problem of focusing an image on the retina; also known as "lazy eye."

Astigmatism: A condition that occurs when the cornea is misshapen to some degree, causing light to focus improperly on the retina.

Cataracts: A condition caused by a clouding of the internal lens of the eye, causing blurred or distorted vision.

Color Vision Deficiency: A genetically inherited trait in which the ability to distinguish some colors is less than normal.

Cornea: The transparent, rounded tissue covering the front of the eye and serving as the first focusing mechanism of light entering the eye.

Diabetic Retinopathy: Associated with diabetes, an eye disease that can lead to blindness.

Farsightedness: See Hyperopia; a condition in which close-up objects appear blurred.

Floaters: Small, cloudy specks of various sizes that form in the vitreous fluid of the eye.

Glaucoma: An eye disease in which the internal pressure of the eye increases; it may cause permanent damage to the optic nerve that can lead to blindness if not properly treated.

Hyperopia (Farsightedness): a condition in which close-up objects appear blurred.

Keratoconus: A disease in which the cornea becomes misshapen, causing blurry vision.

LASIK (Laser-Assisted In Situ Keratomileusis): A type of laser eye procedure used to treat various refractive or focusing errors of the eye. LASIK creates a flap that is opened to expose inner corneal tissue for reshaping, thereby eliminating (or reducing) the corneal refractive error and significantly changing the requirement for corrective eyewear. The procedure is relatively painless with a rapid healing process.

Lens: A crystalline, biconvex tissue within the eye that focuses light rays upon the retina; this is the structure on which cataracts may form.

Macula: The area of the retina responsible for clear, detailed central vision.

Macular Degeneration: A disease in which the macula undergoes vascular or aging changes that may lead to the loss of central vision if untreated.

Myopia: Nearsightedness; a condition in which distant objects appear blurred.

Nearsightedness: a condition in which distant objects appear blurred

Optic Nerve: The nerve that carries visual impulses from the retina directly to the brain.

Pupil: The center of the eye that closes and opens to allow light to properly reach the rest of the eye. 

Presbyopia: A condition related to the normal aging process, in which it becomes difficult to focus on close-up objects.

PRK (Photo-Refractive Keratectomy): A type of laser eye procedure used to treat various refractive or focusing errors of the eye. PRK reshapes tissue on the surface of the cornea, thereby eliminating (or reducing) the corneal refractive error and significantly changing the requirement for corrective eyewear. The procedure, although less surgically invasive, generally requires a longer healing process.

Refraction: The eyes' natural ability to focus light rays properly on the retina.

Retina: The nerve fiber layer or inner surface of the eyeball on which images are projected and delivered to the optic nerve as impulses for transmission directly to the brain.

Sclera: The dense fibrous opaque white outer coat enclosing the eyeball except the part covered by the cornea.

Spots: Small, cloudy specks of various sizes that form in the vitreous fluid of the eye; also called floaters.

Strabismus: A condition in which difficulty with eye muscle balance and coordination causes one or both eyes to turn in, out, up, or down.

Tonometry: A test that measures the internal fluid pressure within the eye. Increased fluid pressure is an indicator in the diagnosis of glaucoma.

Visual Acuity: A test of the eyes' ability to see sharply and clearly at all distances; part of a comprehensive eye exam that may be tested with or without a vision correction.