Definition

Noun: 1. (Optics) A defect in an optical system (such as a lens or mirror) where light rays from a single point do not converge into a single, sharp focal point, resulting in a blurred or distorted image. 2. (Ophthalmology) A common vision condition, also called astigmatism, where the eye's cornea or lens has an irregular curvature. This prevents light from focusing properly on the retina, causing blurred or distorted vision at all distances. It often occurs alongside nearsightedness (myopia) or farsightedness (hyperopia).

Usage Examples

• Noun (Ophthalmology):
  • Her astigmia causes her to see streetlights as elongated streaks rather than sharp points of light.
  • The optometrist diagnosed him with mild astigmia and prescribed corrective lenses.
• Noun (Optics):
  • The telescope's astigmia was corrected by realigning its primary mirror.

Advanced Usage

• "To correct astigmia": This is the standard phrase for describing the treatment, typically with eyeglasses, contact lenses, or refractive surgery.
  • Toroidal contact lenses are specifically designed to correct astigmia.

Variants and Related Words

• Astigmatism (n): The more common, everyday term for the ophthalmological condition. "Astigmia" is a technical synonym.
• Astigmatic (adj): Describing something or someone affected by astigmia.
  • An astigmatic eye requires a cylindrical lens correction.

Synonyms

• (For the vision condition) Astigmatism.
• (For the optical defect) Optical aberration, focal defect.

Related Phrases / Terms

• Regular astigmatism / Irregular astigmatism: Classifications based on the pattern of the corneal irregularity.
• Corneal astigmatism / Lenticular astigmatism: Specifies whether the defect originates in the cornea or the lens of the eye.

Noun

1. (optics) defect in an optical system in which light rays from a single point fail to converge in a single focal point
2. (ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea; common in nearsighted people