I think we forget what free-form lenses primarily do. The first two primary things that free-form acheived was to compensate for the limited base curves of multifocals and bring a lens closer to true form optics, and to solve the issue of Oblique Marginal Astigmatism (which is really a base curve issue too).

As most of you know, every RX should have its own unique base curve, so a -2.00 should be on a different base curve than a -2.50, from a -2.75 etc. We can't do this in multifocals simply because the total amount of blanks necessary would shoot up to about 25,000 for one progressive to cover every base curve in every add power. Its not financially feasable. As a result, we ususally end up with progressive blanks available on only 5 or 6 base curves instead of about 45, which is what we would need.

In single vision, we can solve this with true-or best form finished single vision lenses (or SV aspheric lenses that simulate true form optics) because we can use a SV finished lens for every axis (we just rotate the blank when laying it out). We don't have add powers to stock, so it IS cost effective to make Finished SV using best form or aspheric optics. A stock SV lens made with true form base curves can be stocked cost effectively. In fact the Zeiss Punctal lenses in the 1930's did just this.

The problem with True form optics is that it runs a lot steeper than most people prefer cosmetically, so aspheric lens try to bridge that gap of providing better (simulated true-form optics) on a flatter base curve that is thinner and more appealing cosmetically. We can improve optics immensely simply by using quality aspheric finished SV lens blanks.

In the end either a SV finished True Form lens, or a quality finished aspheric SV (like Zeiss and Seiko) will give vision very close to Free-form, because the goal is same, simulated true form optics.

The variable is the lab. Many labs (for reasons beyond me) grind every lens, even SV, on simple base curves like 2,4,6, 8 etc. Those lenses will NOT be close to true or best form optics. They will not provide optimal vision.

The other issue is that Atoric lenses seem to be disappearing in finished SV (some manufacturers call theirs "double aspheric" now), so cyls over -1.25 will see some benifit in Free-form SV lenses over a stock lens that is not atoric.

So if you use a quality stock SV true form lens, it will give you vision almost indistinguishable from Free-form in lower powers. If you grind every lens, Free-form lenses will seem enormously better


Quote Originally Posted by 12345 View Post
Hi, would anyone here like to share their experiences in prescribing free form single vision lenses for their patients? Is the visual optics provided much better than the conventional lenses? Is the vision much better at night time for free form sv?
Quote Originally Posted by Robert_S View Post
I find that with anything over a +/-2.00 with anything over a 1.00 cyl, the patient will notice a difference.

However, usually the patient will only notice a huge difference if the Sphere is over a +3.00 or -4.00, or if the cyl is above a 2.00, or if they are the engineer type.