1. A lens or optical system having different refractivity in different meridians.

2. A condition of unequal curvatures along the different meridians in one or more of the refractive surfaces (cornea, anterior or posterior surface of the lens) of the eye, in consequence of which the rays from a luminous point are not focused at a single point on the retina. Syn: astigmia.


[G. a- priv. + stigma (stig- mat-), a point]

astigmatism against the rule

compound hyperopic astigmatism

compound myopic astigmatism

corneal astigmatism

hyperopic astigmatism

irregular astigmatism

lenticular astigmatism

mixed astigmatism

myopic astigmatism

astigmatism of oblique pencils

regular astigmatism

simple hyperopic astigmatism

simple myopic astigmatism

astigmatism with the rule