How different are these two prescriptions?

Discussion in 'Glasses' started by NumbersGuy, Sep 12, 2017.

  1. NumbersGuy

    NumbersGuy

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    My wife's distance prescription from 2014:

    ___SPH___CYL__Axis
    OD +.75 -1.50 90
    OS -.50 -1.00 95


    Today she was measured at:

    ___SPH____CYL__Axis
    OD -1.50 +1.75 178
    OS -1.50 +1.25 010


    At first glance it looks extremely different. But then I noticed that the two CYL measurements were actually very similar, looking different only because of the choice of convention used (+ vs. -). Since the second Axis angle are nearly perpendicular to the first Axis angles, I would expect the diopters to be negated.

    We have not yet purchased glasses based on this prescription. My question is, does the choice of presentation for astigmatism affect the comparative interpretation of the spherical? That is, are they really all that different?
     
    NumbersGuy, Sep 12, 2017
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