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Explaining the difference in Axis

Question

Thank you very much for responding to my question about the difference in the two prescriptions below:

Right Eye Sphere: -4.50 Cyl: +1.50 Axis: 105 Left Eye Sphere: -5.25 Cyl: +1.25 Axis: 90

Right Eye Sphere: -3.25 Cyl: -1.50 Axis: 15 Left Eye Sphere: -4.25 Cyl: -1.50 Axis: 176

I understand the explanation about transposing the prescriptions. However, you do not mention the large difference in the Axis numbers. Please could you explain how they are different and if it should make a difference to my vision? Thank you again for your help.

Answer Written answer:
Qualified optometrist Simon Kay BSc(Hons) MCOptom answers this question.

When you transpose the prescription the axis degree changes by 90 degrees, so 105 becomes 15 in the right and 90 becomes 180 in the left which is only four degrees different in this eye. When transposing a prescription you add the sphere to the cyl, change the power of the cyl and change the axis by 90 degrees. So transposing the left eye of the first prescription you get Sphere -4.00, Cyl -1.25, Axis 180. I hope this helps. 

Optician's Biography

Simon Kay BSc(Hons) MCOptom has been a qualified Optometrist for over 30 years, and has a vast experience of almost all aspects of optometry. He joined Specsavers Opticians in 1993 first in Liverpool and for 15 years as a director of Lancaster and Morecambe. He served on many panels and committees whilst a director, including those responsible for IT design and professional advancement. He was regional chairman of the North West directors of Specsavers for over 12 years and as such was involved in almost all aspects of optometry on a business and professional level. He has been involved on the Local Optical Committee for many years and is currently Vice Chairman in his area.
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