Should be same... IIRC only above 400 then got diff
I found an article here....
Converting the ‘cylinder’ number
2) If your glasses ‘cylinder’ number is -0.25 or -0.50
If your glasses prescription has a -0.25 under ‘cylinder’, you can just completely ignore it (and the axis) for your contact lenses. If it shows a -0.50, you can ignore it by adding an extra -0.25 to the ‘shpere’ number. For example, if the glasses prescription shows this:
Sphere Cylinder Axis
Right -5.00 -0.50 180
Left -6.25 -0.50 010
We can ignore the cylinder and axis when ordering contact lenses but we have to adjust the sphere twice. First, to compensate for ignoring the ‘cylinder’ we add an extra -0.25 to the ‘sphere’ number making them -5.25 and -6.50 for right and left eye respectively. Then we would use -5.25 and -6.50 in the vertex conversion chart above and find that our final numbers would be -5.00 and -6.00.
Since my eyeglass prescription is:
Right: -3.00 (Sph) -0.5 (Cyl) 165 (Axis)
Left: -2.75 (Sph) -0.5 (Cyl) 180 (Axis)
For contact lens, i should get:
Right: -3.25 (Sph)
Left: -3.00 (Sph)
Is this conversion correct?
