Common Terms About Eye Health



Also known as "lazy eye," amblyopia is reduced vision in a healthy eye. Vision must develop, and development is impaired when eyes do not focus equally or maintain proper alignment. The brain ignores the information from the less favored eye. In either case, if this condition persists, the weaker eye will not develop normally. In babies, who are learning to use their eyes as a team, it's easier for an eye doctor to distinguish between appropriate development and delays that could signal the need for intervention. Early detection of amblyopia is important because the earlier treatment is started the more effective it may be.


Astigmatism blurs vision at all distances because the optical parts of the eye (cornea and lens) do not focus light onto the retina clearly. This condition is quite common, and results from an unequal curve of the cornea when comparing the horizontal and vertical planes. For descriptive purposes, imagine half of a tennis ball, squeezed at the top and bottom; the ball is now curved unequally. In the eye, this results in inaccurate focus on the retina. Lenses are often used to help focus the light to eliminate blurriness from astigmatism.



Often called farsightedness, hyperopia is when the eyeball is too short for the normal focusing power of the eye. Depending on severity, it can cause blurred vision, eye fatigue and sometimes amblyopia or crossed eyes.


Often called nearsightedness, myopia causes distant objects to appear blurred. The eyeball is too long for the normal focusing power of the eye.


Strabismus occurs when one eye does not aim at the same object being viewed as the other eye. The “eye turn” may be present continuously or only occasionally, and the turn may be inward toward the nose (esotropia) or outward (exotropia), up or down. There is a common misconception that a child will outgrow crossed-eyes. This is not true. Untreated, this condition can lead to amblyopia.


American Optometric Association doctors of optometry are highly qualified, trained doctors, on the frontline of eye health and vision care, who examine, diagnose, treat, and manage diseases and disorders of the eye. In addition to providing eye and vision care, optometrists play a major role in an individual's overall health and well-being by appropriately detecting systemic diseases. Doctors of optometry provide more than two-thirds of all primary eye care in the United States. The American Optometric Association represents more than 36,000 doctors of optometry, optometry students and paraoptometric assistants and technicians in nearly 6,500 communities across the country. For more information, visit

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