98:
184:
20:
479:
As a consequence, there are two different refractive powers at orientations perpendicular to each other. At intermediate orientations, the refractive power changes gradually from the greatest to the smallest value, or reverse. This will compensate for the astigmatic aberration of the eye.
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With modern computer-controlled design, grinding and polishing techniques, good vision corrections can be achieved for even wider angles of view by allowing certain deviations from the toric shape. This is called an
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in two orientations perpendicular to each other. One of the lens surfaces is shaped like a "cap" from a
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369:. The lens behaves approximately like a combination of a spherical lens with optical power
8:
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is based on a mathematical approximation, which is only valid for small corrective powers
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573:, chapter 50 (Lippinkott, Wilkins & Williams / Wolters-Kluwer Health, Chicago, USA)
493:(literally, non-toric lens). They are related to toric lenses in the same way that
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axis) of the torus are refracted according to the smallest radius of curvature,
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rotates around an axis lying within the same plane as the circle, at a distance
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shape. Consequently, in contrast with a popular assumption, the toric lens is
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A torus is the surface of revolution resulting when a circle with radius
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rotates around an axis lying in the same plane as the circle (here the
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This is used for correcting astigmatism. In this context, the term
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approaches 0 (here from right to left), the torus becomes a sphere.
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is produced, where the opening is contracted into a single point.
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23:
Toric lens surface as "cap" (top-right) from a torus (here with
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Light rays within a plane through the axis of revolution (the
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Note that both the greatest and the smallest curvature have a
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457:, which means that it has the smallest refractive power,
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55:(see figure at right), and the other one is usually
128:from the circle's centre (see figure at right). If
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447:according to the greatest radius of curvature,
59:. Such a lens behaves like a combination of a
172: = 0, the torus degenerates into a
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196:Radius of curvature and optical power
67:. Toric lenses are used primarily in
267:{\displaystyle S={\frac {n-1}{R+r}}}
101:A torus results when a circle with
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428:Light ray and its refractive power
334:{\displaystyle s={\frac {n-1}{r}}}
289:The smallest radius of curvature,
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497:are related to spherical lenses.
540:Principles of Atoric Lens Design
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531:
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214:, corresponds to the smallest
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1:
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547:, Vol. 27, No. 3 (Jan. 1998)
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204:of the toric lens surface,
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422:ellipsoid of revolution
286:of the lens material.
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187:When the major radius
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27: = 1.2
571:Duane's Ophthalmology
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112:axis) at a distance
284:index of refraction
202:radius of curvature
168:approaches 0. When
590:Geometrical optics
565:2012-03-12 at the
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77:intraocular lenses
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595:Corrective lenses
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375:cylindrical lens
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216:refractive power
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65:cylindrical lens
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567:Wayback Machine
559:Aspheric Lenses
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495:aspheric lenses
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43:with different
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407:cylinder power
405:is called the
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91:Main article:
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73:contact lenses
61:spherical lens
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200:The greatest
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162:spindle torus
160:results in a
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45:optical power
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435:within the (
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176:with radius
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49:focal length
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34:
28:
24:
16:Type of lens
491:atoric lens
484:Atoric lens
377:with power
297:, given by
222:, given by
81:astigmatism
79:to correct
584:Categories
557:Volk, D.:
525:References
433:Light rays
150:horn torus
138:ring torus
69:eyeglasses
37:toric lens
545:Lens Talk
445:refracted
393:optometry
320:−
245:−
57:spherical
563:Archived
515:cylinder
414:circular
282:is the
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373:and a
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278:where
174:sphere
103:radius
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501:Notes
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