[branney]

My prescription in summer 2007 was:

RIGHT
SPH 0.00
CYL -1.50
AXIS 160

LEFT
SPH -0.25
CYL -0.75
AXIS 7

I got glasses and still use these at work, and they improve my vision. I can see almost as well without them, but find myself frowning/squinting so prefer to wear them, although it is not a problem for me if I forget to bring them one day.

My prescription in summer 2009, from a different shop was:

RIGHT
SPH -1.79
CYL +1.50
AXIS 75

LEFT
SPH -1.00
CYL +0.75
AXIS 100

It looks like the cylinder values have remained to the same extent in each eye, but changed from -ve to +ve. Is this possible, or has a mistake been made with the prescription?

Also, could the axes change completely like this in 2 years? Just seems a coincidence given that the number have not changed, only the +/-.

Note how the axes on each eye have changed by around 90 degrees. If my astigmatism really has changed so much, why do my old glasses still help my vision? Surely having astigmatism and correcting it at the wrong angle by around 90 degrees in each eye would only make it twice as bad!

The shop was quite eager to sell me contacts, but despite 4 visits and 3 hours of trying, I could not get a single lens in, and decided to not bother.
I had to ask for my prescription at the time, and did not get round to ordering new glasses until tonight.

Perhaps fortunately, I decided to compare with the old prescription.
I now get the feeling the shop was up to something - are my suspicions unfounded?

[OpticianGuide]

Branney,

You may see a prescription written with a positive CYL or a negative CYL. Optometrists will write a prescription using a minus-cylinder and generally ophthalmologists will write a prescription using a plus-cylinder notation. When you convert the cylinders, the axis is rotated by 90 degrees.

Hope this helps.