Glossary of Common Eye & Vision Conditions

The American Optometric Association provides doctor-reviewed, doctor-approved information about the most common eye conditions. Find out more below. If you are having vision or eye problems, see an AOA-member optometrist today.

Acanthamoeba Acanthamoeba is one of the most common organisms in the environment, but it rarely causes infections. When infection, called Acanthamoeba keratitis, does occur, it can threaten your vision. The best defense against Acanthamoeba keratitis infection is proper contact lens hygiene.
Accommodative Dysfunction An eye focusing problem that is unrelated to changes in the lens of the eye due to aging.

Anterior Uveitis
Anterior uveitis is an inflammation of the middle layer of the eye. This middle layer includes the iris (colored part of the eye) and adjacent tissue (known as the ciliary body). If untreated, glaucoma, cataract or retinal edema can develop and cause permanent loss of vision. It usually responds well to treatment, but the inflammation tends to recur.
Astigmatism A vision condition that causes blurred vision due either to the irregular shape of the cornea (the clear front cover of the eye) or sometimes the curvature of the lens inside the eye.
Blepharitis An inflammation of the eyelids and eyelashes causing red, irritated, itchy eyelids and dandruff-like scales on eyelashes.
Cataract A cloudy or opaque area in the normally clear lens of the eye located behind the iris.
Chalazion A slowly developing lump that forms due to blockage and swelling of an oil gland in the eyelid.
Color Vision Deficiency The inability to distinguish certain shades of color. The term "color blindness" is also used to describe this visual condition, but very few people are completely color blind.
Computer Vision Syndrome A group of eye and vision-related problems that result from prolonged computer use.
Conjunctivitis A swelling or inflammation of the conjunctiva, the thin, transparent layer of tissue that lines the inner surface of the eyelid and covers the white part of the eye. Causes may or may not be infectious.
Convergence Insufficiency An eye coordination problem in which the eyes drift outward when reading or doing close work.
Corneal Abrasion A cut or scratch on the cornea, the clear front cover of the eye.
Crossed Eyes Crossed eyes, or strabismus, is a condition in which both eyes do not look at the same place at the same time. It usually occurs in people who have poor eye muscle control or are very farsighted.
Diabetic Retinopathy A condition occurring in people with diabetes. It causes progressive damage to the retina, the light-sensitive lining at the back of the eye.
Dry Eye A condition in which there are insufficient tears to lubricate and nourish the eye.
Eye Coordination Eye coordination is the ability of both eyes to work together as a team. Each of your eyes sees a slightly different image. Your brain, by a process called fusion, blends these two images into one three-dimensional picture. Good eye coordination keeps the eyes in proper alignment. Poor eye coordination results from a lack of adequate vision development or improperly developed eye muscle control.
Farsightedness (Hyperopia) A vision condition in which distant objects are seen clearly, but close objects are blurred.
Floaters & Spots The shadowy images that appear in the field of vision caused by particles floating in the fluid that fills the inside of the eye.
Glaucoma A group of disorders leading to progressive damage to the optic nerve. It is characterized by loss of nerve tissue that results in vision loss.
Hordeolum (Sty) An infection of an oil gland in the eyelid.
Keratitis An inflammation or swelling of the cornea, the clear front cover of the eye.
Keratoconus An eye disorder causing progressive thinning and bulging of the cornea, the clear front cover of the eye.
Lazy Eye (Amblyopia) Also known as lazy eye, the loss or lack of development of clear vision in just one eye not due to eye health problems. Eyeglasses or contact lenses can't fully correct the reduced vision caused by lazy eye.
Learning-related Vision Problems Vision disorders that interfere with reading and learning.
Macular Degeneration An eye disease affecting the macula (the center of the light-sensitive retina at the back of the eye), causing loss of central vision.
Migraine with Aura A type of severe headache accompanied by various visual symptoms.
Myokymia Myokymia of the lid is a unilateral and uncontrollable lid twitch or tic that is not caused by disease or pathology. It is thought to be brought on by stress and other similar issues and resolves on its own with time.
Nearsightedness (Myopia) A vision condition in which close objects are seen clearly, but objects farther away are blurred.
Nystagmus A vision condition in which the eyes make repetitive, uncontrolled movements, often resulting in reduced vision.
Ocular Allergies The abnormal response of sensitive eyes to contact with allergens and other irritating substances.
Ocular Hypertension An increase in the pressure inside the eye above the range considered normal without any detectable changes in vision or damage to the structures of the eye.
Ocular Migraine Visual disturbance similar to what can occur with a migraine but without the headache. This visual disturbance can be alarming.
Pinguecula An abnormal growth of tissue on the conjunctiva, the clear membrane that covers the white of the eye.
Presbyopia An age-related vision condition in which the eye gradually loses the ability to focus on near objects.
Pterygium An abnormal growth of tissue on the conjunctiva (the clear membrane that covers the white of the eye) and the adjacent cornea (the clear front surface of the eye).
Ptosis A drooping of the upper eyelid.
Retinal Detachment A tearing or separation of the retina (the light-sensitive lining at the back of the eye) from the underlying tissue.
Retinitis Pigmentosa A group of inherited disorders of the retina (the light-sensitive lining at the back of the eye), which cause poor night vision and a progressive loss of side vision.
Retinoblastoma A rare type of eye cancer occurring in young children that develops in the retina, the light-sensitive lining at the back of the eye.
Subconjunctival Hemorrhage An accumulation of blood underneath the conjunctiva, the clear membrane covering the white part of the eye.

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