Unfortunately, I think you have been misinformed. Several of the points made in this post are not entirely accurate. To assert that the company you are affiliated with, Shamir, only utilizes position of wear measurements for
prescription compensation is one thing. I completely agree that prescription compensation offers only minimal visual benefit to the wearer, as I have described ad nauseam in other threads, including
this post from just a few days ago.
But the assertion that position of wear measurements do not influence optical performance, or that
other lens manufacturers do not utilize these measurements when designing and fabricating free-form lenses, is incorrect. The position of wear can significantly influence optical performance over the entire lens design in many cases.
Basic prescription compensation, on the other hand, only improves vision through a narrow region of the distance zone. Further, any eye care professional can apply this form of prescription compensation to any lens, even semi-finished, using free software tools.
I have included an actual optical comparison of three different lenses, which demonstrates the influence of the position of wear. I would also encourage you to review US Patent 6,089,713, which details the use of position of wear measurements when calculating free-form lens designs.
This, again, refers to the same type of prescription compensation that eye care professionals have been applying for years. Free-form lens designs that are truly customized for the position of wear, on the other hand, utilize the vertex, or
stop, distance to perform optical ray tracing of a lens-eye model in the position of wear. This is completely independent of any vertex compensation applied because of differences between the refracted and fitted vertex distances.
Actually, for a given base curve, the curvature of the frame can only influence optical performance by changing the
position of wear, since decentering a meniscus lens introduces lens tilt. Otherwise, the curvature of the frame has no more effect upon optical performance than the color of the frame.
Now, if you have chosen to
substitute a steeper or flatter base curve in lieu of the manufacturer's recommended base curve to achieve a better fit in a frame, thereby violating "best form" optical principles, sufficiently advanced free-form lens designs with full optical optimization can apply the necessary optical corrections over the lens surface.
But, sadly, the
opinions often expressed on the Internet do not represent
facts. Nevertheless, it would be nice to keep the flow of "disinformation" to a minimum.
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