Difference between revisions of Guide:Reading glasses prescriptions
(Added some explanation that makes room for plus lenses) |
(→Cylinder: Added a table "Effect of including cylinder correction") |
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Cylinder correction means your eye has some level of [[astigmatism]]. | Cylinder correction means your eye has some level of [[astigmatism]]. | ||
Since cylinder correction is in addition to spherical correction, what the cylinder correction does depends on the spherical correction: | |||
{| class="wikitable" | |||
|+ Effect of including cylinder correction | |||
! !! Minus Cyl !! Plus Cyl | |||
|- | |||
! Minus Sphere | |||
| Increases myopia correction || Decreases myopia correction | |||
|- | |||
! Plus Sphere | |||
| Decreases presbyopia correction || Increases presbyopia correction | |||
|} | |||
==Axis== | ==Axis== | ||
[[Axis]] is the degree at which cylinder values are relevant. The correct cylinder value but the wrong axis value would make the correction pretty worthless! When reducing your correction, you should never ever change the axis, especially if you've had that value of axis for a long time. | [[Axis]] is the degree at which cylinder values are relevant. The correct cylinder value but the wrong axis value would make the correction pretty worthless! When reducing your correction, you should never ever change the axis, especially if you've had that value of axis for a long time. | ||
Revision as of 22:09, 10 June 2020
 | This article is under construction. Please help develop it, whatever your level of expertise |
How do you read these complicated things!? Believe it or not, they're actually pretty simple to understand.
Spherical
Spherical is the overall correction, in all directions. It is measured in diopters. A minus value means the lense is used correct myopia and a plus value means it is used to correct presbyopia.
Cylinder
Cylinder is the additional correction in a specific direction of your eye. It is measured in diopters. Think of a straight line going across the surface of your eye at a certain degree. The degree this happens at is your axis.
Cylinder correction means your eye has some level of astigmatism.
Since cylinder correction is in addition to spherical correction, what the cylinder correction does depends on the spherical correction:
| Minus Cyl | Plus Cyl | |
|---|---|---|
| Minus Sphere | Increases myopia correction | Decreases myopia correction |
| Plus Sphere | Decreases presbyopia correction | Increases presbyopia correction |
Axis
Axis is the degree at which cylinder values are relevant. The correct cylinder value but the wrong axis value would make the correction pretty worthless! When reducing your correction, you should never ever change the axis, especially if you've had that value of axis for a long time.
If you don't have any cylinder correction, you will not have an axis value either.