How Do I Calculate What My Regular Contact Lens Prescription Would Be from My Astigmatism Lens Prescription?
March 30th, 2010 | See the Top Answers to this Question Below
My tonic (astigmatism) contact lens prescription is:
-4.75 -0.75 x010 and
-5.00 -1.25 x170
what would my prescription be for regular contacts?
(I know that I wouldn’t be able to see as clear with regular contacts, but I would just like to know)
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Add half the amount of astigmatism to the first number, but allowing for the signs. Ignore the third number ( the direction of the astigmatism).
So:
-4.75 -0.75 x010 => -5.00 or -5.25
-5.00 -1.25 x170 => -5.50 or -5.75
If you are younger or do more driving, I’d opt for the higher power, older or do more office work, I’d opt for the lower.
But it’s a compromise.
(can be handy for single use throwaway lenses for swimming, for example)
For other people precriptions such as
+4.75 -1.50 x010 => +4.00
-5.00 +1.00 x170 => -4.50
You have to have your eye doctor determine this and write you a new prescription.
You don’t need to worry about how to calculate the conversion, for the optician will do that when you go for your prescription.There is a special kind of contact lens on sale that can auto-focus near and far , meaning for those who are short-sighted and yet cannot see near object clearly, like reading should opt for this kind of contact lenses. Not only glasses has this function, now contact lenses too have it.