Crossword clues for astigmatism
Longman Dictionary of Contemporary English
The Collaborative International Dictionary
Ametropia \Am`e*tro"pi*a\, n. [Gr. ? irregular + ?, ?, 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.
Douglas Harper's Etymology Dictionary
Wiktionary
n. 1 (context optics English) A defect of a lens such that light rays coming from a point do not meet at a focal point so that the image is blurred. 2 (context pathology English) A disorder of the vision, usually due to a misshapen cornea, such that light does not focus correctly on the retina causing a blurred image.
WordNet
n. (ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea [syn: astigmia]
(optics) defect in an optical system in which light rays from a single point fail to converge in a single focal point [syn: astigmia] [ant: stigmatism]
Wikipedia
An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances. The term comes from the Greek α- (a-) meaning "without" and στίγμα (stigma), "a mark, spot, puncture".
Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. The two types of astigmatism are regular and irregular. Irregular astigmatism is often caused by a corneal scar or scattering in the crystalline lens, and cannot be corrected by standard spectacle lenses, but can be corrected by contact lenses. The more common regular astigmatism arising from either the cornea or crystalline lens can be corrected by eyeglasses or toric lenses. A 'toric' surface resembles a section of the surface of a Rugby ball or a doughnut where there are two regular radii, one smaller than the other one. This optical shape gives rise to astigmatism in the eye.
The refractive error of the astigmatic eye stems from a difference in degree of curvature refraction of the two different meridians (i.e. the eye has different focal points in different planes). For example, the image may be clearly focused on the retina in the horizontal plane, but not in the vertical plane. Astigmatism causes difficulties in seeing fine detail resulting in blurred vision. Three options exist for the treatment of astigmatism: glasses, contact lenses (either hard contact lenses or toric contact lenses), and refractive surgery.
Usage examples of "astigmatism".
Whenever defects in focusing are present, particularly in astigmatism, extra work is thrown on the ciliary muscle as well as the muscles that move the eyeballs.
In fact, a blind ophthalmologist is not much good to anyone, but it was up to him to inform the health authorities, to warn them of this situation which might turn into a national catastrophe, nothing more nor less, of a form of blindness hitherto unknown, with every appearance of being highly contagious, and which, to all appearances, manifested itself without the previous existence of earlier pathological symptoms of an inflammatory, infectious or degenerative nature, as he was able to verify in the blind man who had come to consult him in his surgery, or as had been confirmed in his own case, a touch of myopia, a slight astigmatism, all so mild that he had decided, in the meantime, not to use corrective lenses.
A mild childhood astigmatism worsened when she was thirteen: she started bumping into things and found it increasingly difficult to concentrate on the entomological textbooks and journals that she read voraciously.
Physical astigmatism is a distortion of the eye lenses that causes rays of light from an external point to converge unequally and form warped images.
Up to a point he had made considerable progress with the muscle imbalance that caused the astigmatism which affected all three of his eyes.
I have got rid of all the astigmatism in my right or left eye, yet center eye persists in being astigmatic, sometimes to the point of blindness.
He’ll be the glass, full of subtle colors and astigmatisms, through which all new things will be viewed.
He'll be the glass, full of subtle colors and astigmatisms, through which all new things will be viewed.
When you see a man with the lines of his face drooping, a healthy individual with a pensive eye, - suspect astigmatism.