dioptre

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dioptre

A measure of lens power. The reciprocal of the focal length in metres. A lens of 1 m focal length has a power of 1 dioptre. A lens of 50 cm focal length has a power of 2 dioptres. One of 33.3 cm focal length has a power of 3 dioptres. Dioptres are used by opticians in preference to focal lengths because they can immediately be added together or subtracted during vision testing.

dioptre

1. A unit proposed by Monoyer to evaluate the refractive power of a lens or of an optical system. It is equal to the product of the refractive index in the image space and the reciprocal of the focal length in metres. (Symbol: D.) Thus a lens with a focal length (in air) of 1 m has a power of 1 D, one with a focal length of 1/2 m, has a power of 2 D, etc. 2. It is also incorrectly used to represent a unit of curvature, being equal to the reciprocal of the radius of curvature expressed in metres. See curvature of a surface; myodioptre; fundamental paraxial equation; refractive error; vergence.
Fig. D3 Effect of an 8 Χ prismenlarge picture
Fig. D3 Effect of an 8 Χ prism

Table D3 Relationship between dioptres and focal length (in air)
focal length
dioptre value(cm)(in)
0.25400157
0.5020079
1.0010039
1.506726
2.005020
2.504016
3.0033.313
4.002510
5.00207.9
6.0016.76.6
7.0014.35.6
8.0012.54.9
9.0011.14.4
10.00103.9
12.008.33.3
14.007.12.8
16.006.22.4
20.005.02.0

Table D4 Relationship between prism dioptres and degrees
prism
dioptres (Χ)
degrees (º)minutes ()
10.573º0º34′
21.14º1º8′
31.71º1º43′
42.28º2º17′
52.85º2º51′
63.43º3º26′
74.0º4º0′
84.57º4º34′
95.14º5º8′
105.71º5º43′
158.57º8º34
References in periodicals archive ?
The availability of quarter diopters is another unique distinction that Crystalens enjoys.
July 13 /PRNewswire/ -- Bausch & Lomb announced today that it has received approval from the Food and Drug Administration (FDA) to market the Crystalens HD(TM) in quarter diopter steps in the United States.
The company will begin shipping the Crystalens HD in the additional diopter steps on July 16, 2009.
Out of the 56 million patients, the Company estimates that the target market for the lens, based on the range of diopters recommended for approval by the panel, is approximately 8 million people.
The FDA will consider these recommendations as it completes its expedited review of the ICL Pre-Market Approval application for the -3 to -20 diopter range that was submitted on May 8, 2003.
He has successfully treated more than 50 patients enrolled in the clinical study, all with prescriptions greater than -8 diopters, and up to -20 diopters.
I wanted to do LASIK, but it wasn't an option for me because of my poor eyesight and the thinness of my cornea," said Chuck Thompson, a New York City lawyer whose prescription was a debilitating -15 diopters.
The Verisyse lens implant is approved for the treatment of nearsightedness for prescriptions as high as -20 diopters.
1 diopters and the LASIK surgery patients had a slightly lower level of myopia at an average of minus 9.
We continue to see strong growth in the Visian ICL throughout the world and believe that the newly expanded Visian ICL diopter ranges launched here at ESCRS more than doubles the market opportunity for Visian and allow us to compete directly within the most popular myopic and hyperopic ranges of treatment with LASIK.
His data showed that with less than a 2 diopter offset, on average his patients could achieve 20/20 distance vision and 20/25 near vision.