corneal astigmatism


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astigmatism

 [ah-stig´mah-tizm]
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.

cor·ne·al a·stig·ma·tism

astigmatism due to a defect in the curvature of the corneal surface.

cor·ne·al a·stig·ma·tism

(kōr'nē-ăl ă-stig'mă-tizm)
Astigmatism due to a defect in the curvature of the corneal surface.
References in periodicals archive ?
These are an option for patients who are motivated to be completely independent of glasses and who also have corneal astigmatism.
The corneal astigmatism of the leprosy patients and non-leprosy patients were classified as mild (< 2 D), moderate (2-<4 D), severe (4-< 6 D), or very severe ([greater than or equal to] 6 D).
In addition to clinical appearance, other important parameter that we analysed was induced corneal astigmatism.
Our study has highlighted that TE CXL is a safe and effective procedure with statistically significant reduction in corneal astigmatism, SE and Kmax with reasonable gain in Snellen's visual acuity.
There was no evidence that the lens or other internal structural elements of the eye were actively compensating for corneal astigmatism," says Dr.
In the present study, manual keratometer was used to study corneal astigmatism at central 3 mm before and after pterygium excision with CLAG.
16) found comparable repeatability for posterior corneal astigmatism between Galilei and Pentacam devices, with ICC values of 0.
Surgeons should not risk patients by not applying sutures if there is no significant difference between corneal astigmatism of sutured and sutureless incision.
Mean UCVA and corneal astigmatism before treatment were 0.
The fluid beneath rigid lenses, irrespective of design, will correct anterior corneal asymmetry and irregularity, whether in the form of regular corneal astigmatism or those that cause higher order aberrations and irregular astigmatism.