Difference between revisions of Diopters
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(Added unit symbols, added some math formatting, cleared up some confusing range formatting.) |
Dlskidmore (talk | contribs) m (formatting) |
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<math>D = \frac{1}{f}</math> | <math>D = \frac{1}{f}</math> | ||
In [[EM]] we refer to the [[cm measurement]] to calculate diopters needed to correct [[refraction]] of the eye. If you can see 50cm clearly your diopters will be <math>\frac{1}{0.50}=2dpt</math>. | * In [[EM]] we refer to the [[cm measurement]] to calculate diopters needed to correct [[refraction]] of the eye. If you can see 50cm clearly your diopters will be <math>\frac{1}{0.50}=2dpt</math>. | ||
Lenses in series add their powers : if you're wearing -2 diopter contacts ([[vertex distance|adjusted for glasses strength]]) and put +1 diopter reading glasses over the contacts you're in effect wearing -1 diopters. | |||
A lens with a negative diopter sign compensates for [[nearsightedness]] while a lens with a positive diopter sign compensates for [[farsightedness]]. | * Lenses in series add their powers : if you're wearing -2 diopter contacts ([[vertex distance|adjusted for glasses strength]]) and put +1 diopter reading glasses over the contacts you're in effect wearing -1 diopters. | ||
* A lens with a negative diopter sign compensates for [[nearsightedness]] while a lens with a positive diopter sign compensates for [[farsightedness]]. | |||
{| class="wikitable" | {| class="wikitable" |
Revision as of 02:04, 15 June 2020
Diopter is a measure of the power of a lens (or mirror) and is equal to the reciprocal of focal length in meters. The unit symbol for diopters is dpt, D, or m-1.
- In EM we refer to the cm measurement to calculate diopters needed to correct refraction of the eye. If you can see 50cm clearly your diopters will be .
- Lenses in series add their powers : if you're wearing -2 diopter contacts (adjusted for glasses strength) and put +1 diopter reading glasses over the contacts you're in effect wearing -1 diopters.
- A lens with a negative diopter sign compensates for nearsightedness while a lens with a positive diopter sign compensates for farsightedness.
0.00 to -0.75 dpt | Probably don't need glasses |
-1.00 to -2.00 dpt | Mild myopia, no differentials needed |
-2.00 to -5.00 dpt | Moderate myopia, glasses always needed |
-5.00 to -10.00 dpt | High myopia |
-10.00+ dpt | Very high myopia. Field of view significantly reduced. |