astigmatism

/uh-stig-muh-tiz-uhm/US // əˈstɪg məˌtɪz əm //UK // (əˈstɪɡməˌtɪzəm) //

散光,乱射散光,乱射,乱射光

Definitions

n.名词 noun

1
- : Also called a·stig·mi·a [uh-stig-mee-uh]. /əˈstɪg mi ə/. Ophthalmology. a refractive error of the eye in which parallel rays of light from an external source do not converge on a single focal point on the retina.
- : Optics. an aberration of a lens or other optical system in which the image of a point is spread out along the axis of the system.

This is further backed by statistics regarding astigmatism, a condition that affects almost 33% of the US population.
When a child holds his head to one side constantly on looking at objects, astigmatism, an error of eyesight, is usually indicated.
This is usually attributed to the presence of an irregular astigmatism situated near the asymmetric meridian.
If the subject cannot read up to the twenty-foot line, nearsightedness or astigmatism is indicated.
Short sight or long sight is often associated with astigmatism, so that suitable spectacles cannot be very easily provided.
If the lines appear with unequal distinctness, some irregularity of refraction (astigmatism) is indicated.