Difference between revisions of Chromatic Aberration
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The chromatic aberration expected during a normal eye exam is about a half diopter difference between red and green. This can be a handy test to dial in a final prescription by looking at text on red and green backgrounds and seeing which is clearer. For a standard [[Prescription]], if the green side is clearer, a quarter diopter of sphere is added, if the red side is clearer, a quarter diopter is removed. If the optometrist is trying to introduce a small amount of [[Myopic defocus]] he/she wants the red side clear. | The chromatic aberration expected during a normal eye exam is about a half diopter difference between red and green. This can be a handy test to dial in a final prescription by looking at text on red and green backgrounds and seeing which is clearer. For a standard [[Prescription]], if the green side is clearer, a quarter diopter of sphere is added, if the red side is clearer, a quarter diopter is removed. If the optometrist is trying to introduce a small amount of [[Myopic defocus]] he/she wants the red side clear. | ||
<youtube>WP6eeoyB9go</youtube> | |||
= External Sources = | = External Sources = | ||
* | * [[Wikipedia:Chromatic aberration]] | ||
* | * [[Wikipedia:Duochrome test]] | ||
==References== | ==References== |
Revision as of 13:49, 9 July 2020
Chromatic aberration is probably most easily understood as a prism effect. When light shines through a prism, you see that different colors of light bend (undergo Refraction) differently and create a rainbow effect. When light shines through any lens, including glasses and the natural lens of your eye, the same occurs to a lesser degree. The effect of this is that the Focal Length of the lens is not exactly the same for all colors of light.
Duochrome test
KH | HK |
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EPO | OPE |
The chromatic aberration expected during a normal eye exam is about a half diopter difference between red and green. This can be a handy test to dial in a final prescription by looking at text on red and green backgrounds and seeing which is clearer. For a standard Prescription, if the green side is clearer, a quarter diopter of sphere is added, if the red side is clearer, a quarter diopter is removed. If the optometrist is trying to introduce a small amount of Myopic defocus he/she wants the red side clear.