mixed astigmatism

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an error of refraction in which a ray of light is not sharply focused on the retina, but is spread over a more or less diffuse area; it is due to differences in curvature in the refractive surfaces (cornea and lens) of the eye. adj., adj astigmat´ic. Its exact cause is not known; some common types of astigmatism seem to run in families and may be inherited. Probably everyone has some astigmatism, since it is rare to find perfectly shaped curves in the cornea and lens, but the defect is rarely serious. If the refractive error is troublesome, corrective lenses may be needed.
compound astigmatism that in which both principal meridians are either hyperopic (compound hyperopic astigmatism, with rays coming into focus behind the retina) or myopic (compound myopic astigmatism, with rays coming into focus in front of the retina).
corneal astigmatism that due to the presence of abnormal curvatures on the anterior or posterior surface of the cornea.
hypermetropic astigmatism hyperopic astigmatism.
hyperopic astigmatism that in which the light rays are brought to a focus behind the retina.
irregular astigmatism that in which the curvature varies in different parts of the same meridian or in which refraction in successive meridians differs irregularly.
lenticular astigmatism astigmatism due to defect of the crystalline lens.
mixed astigmatism that in which one principal meridian is hyperopic and the other myopic.
myopic astigmatism that in which the light rays are brought to a focus in front of the retina.
regular astigmatism that in which the refraction changes gradually in power from one principal meridian of the eye to the other, the two meridians always being at right angles; this condition is further classified as being against the rule when the meridian of greatest refractive power tends toward the horizontal, with the rule when it tends toward the vertical, and oblique when it lies 45 degrees from the horizontal and vertical.

mixed a·stig·ma·tism

astigmatism in which one meridian is hyperopic whereas the one at right angle to it is myopic.

mix·ed a·stig·ma·tism

(mikst ă-stig'mă-tizm)
A vision defect in which one meridian is hyperopic while the one at a right angle to it is myopic.

mixed astigmatism

Astigmatism in which one meridian is myopic and the other hyperopic.
See also: astigmatism
References in periodicals archive ?
to evaluate the safety and effectiveness of mixed astigmatism treatment with the ALLEGRETTO WAVE.
This newest approval for the ALLEGRETTO WAVE met all established FDA safety and efficacy targets and achieved similar visual outcomes as we have seen with wavefront-guided treatments for mixed astigmatism.
With the introduction of CustomVue mixed astigmatism, VISX is now the only U.
Forward-looking statements in this release, including statements about the quality of the CustomVue treatment for mixed astigmatism, including that it has the potential to deliver better vision than contacts or glasses, and that VISX and AMO currently anticipate closing the transaction in the second quarter of 2005 are based on information available to the Company as of the date hereof.
In addition, a large number of people with natural or induced mixed astigmatism had no approved treatment to turn to at all.
That changed with the FDA's approval of the Alcon Summit Autonomous LADARVision system for treating hyperopia with or without astigmatism and for treating mixed astigmatism using the LASIK procedure.
NASDAQ: BEAM) announced today that the Food and Drug Administration (FDA) Ophthalmic Advisory Panel has unanimously recommended approval of Autonomous Technologies' Pre-market Application (PMA) Supplement for treatment of hyperopia with or without astigmatism and mixed astigmatism using LASIK, with conditions.