Originally Posted by
MakeOptics
Right eye:
-9.00 has a focal length of 1/-9.00 = -0.1111m or -111.1mm, if you are going to pull that lens out further from 11mm to 14.5mm that's moving the lens 14.5-11 = 3.5mm further out, so we adjust the focal length by -111.1 + 3.5 = -107.6mm or -0.1076m which has a dioptric value of 1/-0.1076 = -9.29D is the compensated power which is what you would order from the lab.
Left Eye same procedure but you need to compensate both meridians powers separately then compare them to get you new cylinder value:
Power@045 = -8.50D
Power@135 = -6.50D
@45/ 1/-8.50 = -0.1176m or -117.6mm
-117.6 + 3.5 = -114.1mm or -0.1141m
1/-0.1141 = -8.76D
@135/ 1/-6.50 = -0.1538m or -153.8mm
-153.8 + 3.5 = -150.3mm or -0.1503m
1/-0.1503 = -6.65D
-8.76/2.11 x 045
Step through the problem using simple procedures instead of long formulas.
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