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This is my glasses prescription, is the cylinder minus applied at the meridians 180 and 10? So the the light is diverged at 180 and 10? Or does the axis value refer to the horizontal axis of a cylinder lens or plano, where there is 0 diopters?

And also, how does the conversion between -CYL and +CYL power work?

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Your right eye has a +075 diopters spherical lens combined with a cylindrical with a power of -2.25 diopters and the axis of $180^{\circ}$ or horizontal.

Your Left eye has a +1 spherical and a -2.25 cylindrical with its axis $10^{\circ}$ from the horizon.

As a rule of thumb, prescription lenses can not be more powerful than about 10 diopters. They have to use an assembly of lenses like a telescope for powers greater than that for many reasons, one being the separation of colors of the light into a rainbow.

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  • $\begingroup$ I dont think you're understanding. Is the -2.25 diopters applied to the axis 10? Or does is axis 10, representative of the plano axis? And therefore the SPH power of +1 is used at axis 10? $\endgroup$ Commented Jan 14, 2022 at 1:38
  • $\begingroup$ Sphere means the lens is symmetrical. It means you can rotate the lens in the frame randomly and it will be still the same. The -2.25 is with an axis of 180 degrees. I fail to see what part of this is not clear. I myself used to wear cylindrical lenses for many years, then I did Lasic surgery. You can verify with the eye doctor who examined your vision.? $\endgroup$
    – kamran
    Commented Jan 14, 2022 at 2:01
  • $\begingroup$ To your last comment -- modern optometric plastics have rather low dispersion. It's rare, even for high power, to see a 2-element sandwich (different materials) in use. $\endgroup$ Commented Jan 18, 2022 at 14:58

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