astigmatism

Definitions

  • WordNet 3.6
    • n astigmatism (optics) defect in an optical system in which light rays from a single point fail to converge in a single focal point
    • n astigmatism (ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea; common in nearsighted people
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Webster's Revised Unabridged Dictionary
    • n Astigmatism (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.☞ 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.
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Century Dictionary and Cyclopedia
    • n astigmatism In ophthalmology, a defect in the refractive apparatus of the eye, the curvature of the refracting surfaces being greater along certain meridians than along others, so that rays of light proceeding from an external point do not converge to a point upon the retina, but to a line.
    • n astigmatism A similar defect in a lens.
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Chambers's Twentieth Century Dictionary
    • n Astigmatism a-stig′ma-tizm a defective condition of the eye, in which rays proceeding to the eye from one point are not correctly brought to a focus at one point
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Etymology

Webster's Revised Unabridged Dictionary
Gr. 'a priv. + , , a prick of a pointed instrument, a spot, fr. to prick: cf. F. astigmatisme,
Chambers's Twentieth Century Dictionary
Gr. a, neg., and stigma, stigmat-os, a point.

Usage

In literature:

And it is neither thimbleriggery nor astigmatism.
"The Trimmed Lamp" by O. Henry
But I'm doing this with no astigmatism.
"The Money Master, Complete" by Gilbert Parker
The trouble was merely a slight astigmatism which bothered me only in reading or close inspection.
"The Mystery" by Stewart Edward White and Samuel Hopkins Adams
It was simply a case of connubial astigmatism.
"The Love Affairs of Great Musicians, Volume 2" by Rupert Hughes
They belonged to a person who was near-sighted and astigmatic in the left eye and almost certainly blind in the right.
"The Mystery of 31 New Inn" by R. Austin Freeman
There seems to be a sort of astigmatism that keeps us from seeing things straight.
"Quiet Talks on Service" by S. D. Gordon
B. is moderately myopic and very astigmatic in the left eye; extremely myopic in the right.
"The Humour of Homer and Other Essays" by Samuel Butler
Was the editor's inner vision really so curiously astigmatic?
"Queed" by Henry Sydnor Harrison
We do not say of Love that he is astigmatic.
"A Christmas Garland" by Max Beerbohm
Of six cows, five were hypermetropic and astigmatic and one was slightly myopic.
"Scientific American Supplement No. 822" by Various
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In news:

Astigmatism - part 1.
GP lenses have an important advantage over soft lenses in that the tear layer between the lens and cornea (lacrimal lens) has astigmatic power.
Therefore, all of the astigmatic correction has to be in the lens itself.
Custom soft bifocals with special needs, including astigmatism, can be ordered directly from a manufacturer consultant, our best friend for success.
But because John has astigmatism and other medical problems.
Our consultant recruited a 61-year-old woman as the shopper, equipping her with six copies of a bifocal prescription to correct her farsightedness and astigmatism and six identical plastic eyeglass frames.
When LASIK isn't the answer, these lenses may offer an alternative for patients with myopia and astigmatism.
Each year, about a million people elect to undergo this procedure, which is designed to correct nearsightedness, farsightedness, and astigmatism.
The company claimed that its soft spherical lens could mask anywhere from ­0.50D to ­2.00D of astigmatism.
A 25-year-old Caucasian male with a history of moderate myopia and low astigmatism presented to the contact lens clinic specifically for a Duette fitting.
You might have a slight astigmatism, which makes it harder for your eyes to adapt to darkness.
If visual acuity is less than expected, an SCOR may help determine if uncorrected astigmatism is the culprit.
Soft Torics are the Lenses of First Choice for Astigmatism.
When Correcting Astigmatism, Vote Yes to GP Lenses.
A topographical image of the patient's right eye with a moderate 1.40D corneal astigmatism.
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In science:

The contribution of higher order aberrations (astigmatism and coma) is strongly dependent both on the window working angle and the beam fnumber.
Design of the wavefront sensor unit of ARGOS, the LBT laser guide star system
Given a certain system f-number coma is the dominant aberrations at smaller angles on incidence on the optic surface, while astigmatism dominates at larger angles.
Design of the wavefront sensor unit of ARGOS, the LBT laser guide star system
For the same reason given a certain incidence angle, coma dominates for faster beams and astigmatism dominates for slower beams.
Design of the wavefront sensor unit of ARGOS, the LBT laser guide star system
Figure 3.4: Plot of the difference factor between coma and astigmatism, taken from .
Design of the wavefront sensor unit of ARGOS, the LBT laser guide star system
For a given beam f-number the incidence angle at which coma equals astigmatism can be evaluated as follows: identify the f-number value on the x-axis, follow the vertical line to the astigmatism curve and then the horizontal line to the coma curve.
Design of the wavefront sensor unit of ARGOS, the LBT laser guide star system
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