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astigmatism    音标拼音: [əst'ɪgmət,ɪzəm]
n. 散光

散光

astigmatism
n 1: (ophthalmology) impaired eyesight resulting usually from
irregular conformation of the cornea; common in nearsighted
people [synonym: {astigmatism}, {astigmia}]
2: (optics) defect in an optical system in which light rays from
a single point fail to converge in a single focal point [synonym:
{astigmatism}, {astigmia}] [ant: {stigmatism}]

ametropia \am`e*tro"pi*a\ ([a^]m`[-e]*tr[=o]"p[i^]*[.a]), n.
[Gr. 'a`metros irregular 'w`ps, 'wpo`s, eye.] (Med.)
A visual impairment resulting from faulty refraction of light
rays in the eye. Subtypes include {myopia} {astigmatism} and
{hyperopia}. -- {Am`e*trop"ic} ([a^]m`[-e]*tr[o^]p"[i^]k), a.
AS
[1913 Webster PJC]


Astigmatism \A*stig"ma*tism\, n. [Gr. 'a priv. ?, ?, a prick
of a pointed instrument, a spot, fr. ? to prick: cf. F.
astigmatisme.] (Med. & Opt.)
A defect of the eye or of a lens, in consequence of which the
rays derived from one point are not brought to a single focal
point, thus causing imperfect images or indistinctness of
vision.
[1913 Webster]

Note: The term is applied especially to the defect causing
images of lines having a certain direction to be
indistinct, or imperfectly seen, while those of lines
transverse to the former are distinct, or clearly seen.
[1913 Webster]


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  • Astigmatism: Causes, Symptoms, Diagnosis, and Treatment - WebMD
    Astigmatism - Learn more about the causes, symptoms, diagnosis, and treatment of this condition in which your eye isn’t completely round
  • Astigmatism - Wikipedia
    Astigmatism, whether it is regular or irregular, is caused by some combination of external (corneal surface) and internal (posterior corneal surface, human lens, fluids, retina, and eye-brain interface) optical properties In some people, the external optics may have the greater influence, and in other people, the internal optics may predominate Importantly, the axes and magnitudes of
  • Astigmatism: What It Is, Symptoms, Tests Treatment
    Astigmatism is a common issue that makes your vision blurry Learn what causes it and how eye doctors manage it
  • Astigmatism Explained: Causes, Diagnosis, Treatment - American Academy . . .
    What Is Astigmatism? Astigmatism is an imperfection in the normal curvature of your eye’s cornea or lens In this article: Video: What Is Astigmatism? What Causes Astigmatism? How Does Astigmatism Affect Vision? How Can You Tell if You Have Astigmatism? How Is Astigmatism Diagnosed? How Is Astigmatism Corrected? What Do Astigmatism Measurements Mean on Your Eye Prescription? Video: LASIK for
  • Astigmatism - National Eye Institute
    Astigmatism is a common eye problem that can make your vision blurry or distorted It happens when your cornea (the clear front layer of your eye) or lens (an inner part of your eye that helps the eye focus) has a different shape than normal Learn about the symptoms, causes, diagnosis, and treatment of astigmatism
  • What Is Astigmatism? Causes And Effective Treatments
    Causes of Astigmatism Astigmatism primarily arises from irregularities in the shape of the cornea or lens So, what are the most common causes of astigmatism that you should be aware of? Congenital astigmatism: This is the most common cause of astigmatism Many people are born with an irregularly shaped cornea or lens
  • Astigmatism - Symptoms causes - Mayo Clinic
    Astigmatism (uh- STIG-muh-tiz-um) is a common and generally treatable imperfection in the curvature of the eye that causes blurred distance and near vision Astigmatism occurs when either the front surface of the eye (cornea) or the lens inside the eye has mismatched curves Instead of having one curve like a round ball, the surface is egg-shaped
  • Astigmatism Glasses, Lens, Vision Test, Causes, Treatment
    Astigmatism is an eye condition in which the cornea is abnormally curved and causes out-of-focus vision Learn about the causes, symptoms, diagnosis, and treatment
  • Astigmatism - Harvard Health
    What is astigmatism? Astigmatism means that the cornea of the eye has an irregular shape, causing vision problems The cornea is the clear covering over the lens and the iris It protects these structures and helps to transmit light through the eye The cornea is normally spherical, although in people
  • Astigmatism: Causes, Definition, Types, Treatment - All About Vision
    Astigmatism is an irregular curve in your eye that can cause blurry vision and other symptoms Here's how an eye doctor can help you see clearly again





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