Originally Posted by
Darryl Meister
Keep in mind that a compensated prescription is just a small tweak to the original refraction to account for the power changes introduced by lens tilt through one particular point on the lens (within the distance checking circle). A free-form progressive lens that has truly been optimized for the position of wear applies this type of correction at multiple points across the entire lens surface using optical ray tracing. The interaction of the progressive optics with the optical errors introduced in the position of wear -- for a given prescription -- can become quite complex, blurring and distorting the shape of the central viewing zones of the lens.
In reality, the benefits derived from the "compensated prescription" are small compared to the benefits derived from optimizing the entire lens design for the position of wear. In fact, if you are using a free-form progressive lens that has simply had the prescription tweaked for lens tilt, without correcting multiple points across the lens using optical ray tracing, additional optical errors will actually be introduced over much of the lens. The correct prescription will only be experienced over a very small area of the lens. I will try to post some examples, once I return from VisionExpo.
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