Difference between revisions of Guide:Reducing differentials
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===Example=== | ===Example=== | ||
Suppose you have [[Guide:OD/OS|OD/OS]] -4.25/-3.25, and you see, or want to see your monitor | Suppose you have [[Guide:OD/OS|OD/OS]] -4.25/-3.25, and you see, or want to see your monitor 57cm away from where you sit. | ||
Go to the [https://endmyopia.org/focal-calculator/calc.html calculator], and enter in | Go to the [https://endmyopia.org/focal-calculator/calc.html calculator], and enter in 57cm. The result is '''-1.75'''. Subtract this value from both of your eyes (be careful with negative numbers). | ||
<math>OD\ (right\ eye): -4.25-(-1.75)=-2.5</math> | <math>OD\ (right\ eye): -4.25-(-1.75)=-2.5</math> | ||
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<math>OS\ (left\ eye): -3.25-(-1.75)=-1.5</math> | <math>OS\ (left\ eye): -3.25-(-1.75)=-1.5</math> | ||
So, you should use OD/OS -2.5/-1.5, if | So, you should use OD/OS -2.5/-1.5, if 57cm is the main distance you perform [[close-up activity]]. Simple! | ||
If you get a positive number, read the caveats about [[plus lenses]]. | |||
==References== | ==References== | ||