- A lens or optic system having different refractivity in different meridians.
- 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.
[G. a- priv. + stigma (stigmat-), a point]
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Examples: glitazone, GI cocktail, etc.