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 ?
Surgically induced astigmatism was calculated using online SIA calculator for both groups and residual astigmatism was calculated by subtracting post operative from pre operative diopter of astigmatism.
The highest power for Onufryk is 20 diopters, due to the thickness of the prism and keeping in mind the individual's comfort.
Implantable collamer lenses can help people with very high myopia (worse than -12 diopters), while those with extreme hyperopia (worse than +6 diopters) should wait until they need cataract surgery, Dr.
A day-to-night offset of 1/2 or 3/4 diopter * is typical, says Bowen, who prescribes night-driving glasses for some patients.
"You can be 20 feet away and see the different colors corresponding to the 1.25 or 3 diopter, or the 2.75 or 2.5.
Phase III Intacs patients and 46 LASIK patients, all treated for -1.0 to -4.0 diopters of myopia at Hunkeler Vision Centers in Kansas City.
Phase III study of 350 people who were treated for -1.0 to -3.5 diopters of myopia.
Also by FDA approval, the software will not allow a doctor to change the curvature of the eye by more than six diopters, a limit that would exclude people with the worst cases of nearsightedness.
There were differences in steepest keratometry of 47.35 diopters in patients with DS versus 43.7 diopters in control subjects.
Of the 31 eyes, 2 eyes had SE over -18.00 D, in which one eye had cylindrical diopters that have been undercorrected and the other eye had both the cylindrical and the spherical diopters that have been undercorrected; three eyes had preoperative cylindrical diopters from -4.25 D to -5.50 D, and a cylindrical undercorrection of -1.25 D to -1.50 D was designed.
Cataract treatment company RxSight Inc reported on Wednesday the receipt of approval from the US Food and Drug Administration (FDA) for the RxSight Light Adjustable Lens and the Light Delivery Device (LDD) for patients with pre-existing astigmatism of >= 0.75 diopters undergoing cataract surgery.
The mean astigmatism measured by corneal topography at final examination was 5.8[plus or minus]2.3 diopters in group 1 and 5.4[plus or minus]1.8 diopters in group 2.