Astigmatism
uh-STIG-muh-tiz-uhm
/əˈstɪɡ.mə.tɪz.əm/
A defect in the eye or lens caused by an uneven curvature, preventing light rays from focusing properly on a single point on the retina.
Causes distorted or blurred vision at all distances, often producing streaks around lights at night.
The story behind the word. Coined by polymath William Whewell in 1846 from Greek 'a-' (without) and 'stigma' (point). The name literally means 'without a single focal point', describing how irregular cornea shapes scatter focal points.
Word relationships
- refractive error: A broader umbrella term encompassing myopia, hyperopia, and astigmatism.
Commonly confused with
- Stigma: A mark of disgrace; astigmatism is an optical condition stemming from 'a-' (without) and 'stigma' (focal point).
Word family
- astigmatic (adjective): Affected by or pertaining to astigmatism.
Collocations
- corneal astigmatism
- correct astigmatism
- degree of astigmatism
Example sentences
- "Because of her astigmatism, streetlights during night driving appeared stretched into long luminous streaks." Vision assessment
Memory hook
A-STIGMA-tism: Without (A) a single focal point (STIGMA). No single focal point.
When not to use
Do not break into two words ('a stigma'), as astigmatism is a single term.
Fun facts
- Instead of being spherical like a basketball, an astigmatic cornea is shaped more like an oval football.
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