How can one find the spherical equivalent of an eyeglass Rx such as +3.00 -2.00 x165?

Question

i meant....with an eyeglass Rx...such as a person with astigmatism needing an over the counter reader. Some other opticians have told me that is is actually the same as total power at the 180 merridian....is that incorrect? I have also heard it done your way as well...

Answer 1

What ?

What do you mean...a spherical  equivalent. ?

If you mean for contacts...that will never work.

There is no sph equivalent for an Rx like that.

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So, that is his reading Rx already ?

With that amount of astigmatism correction needed ( 2.00)..an over the counter reader won't be very helpful.

A sphere power reader will magnify, but won't eliminate the blur that all that astigmatism causes.

Answer 2

With amount of correction you need for astigmatism you won't find a sherical equivalent that gives you the proper vision.

Answer 3

spherical equivalent = sphere + 1/2(cylinder)

so in your case:

spherical equivalent = +3.00 + 1/2(-2.00) = +2.00

This is how you find the spherical equivalent, but footprintz is right that it won't be accurate for contacts if that is what you are asking for.