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?
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?
Prtescribing? No. Recommending, calculating and fabricating? Yes.
They're wonderful.
No ifs, ands or buts.
B
+1 Barry, right on the money!Originally Posted by Barry Santini
My patients love them. Makes me wish I wore glasses so I could "see" what its all about. They "see"m to live up to the hype.
Some times I agree with Barry Santini and this is one of them. I wear them and think they are much better.
I usually argue that SV is a better example of the benefits of Freeform than PALs. PALs will always have a corridor and can never be made in violation of the minkwitz theorem. so the global design benefit that a well compensated freeform design can have is mostly in the distance area of a PAL, where as in a Freeform SV you can truly create edge to edge to edge clarity. this is especially true in higher prescritions, patients with astigmatism, and anytime you move a way from the ideal base curve.
+1
I have had good success with the freeform single vision. Especially as the power increases. I don't personally notice a difference, but I am only a -0.25 -0.75. My brother in law is a -6.75 sph and loves the wider field of vision that it gives him.
I would disagree. Using Minkwitz a little, I think there is an enormous advantage in a backside add power in a myope, decreasing with increased hyperopia, to lower total distortion. To use the old sand analogy for progressive lens distortion, it simply takes less sand to fill a bowl (like when we put the add on the back of a progressive) than when put the add on the front, because we are building a dome with sand. It will take more sand to build that dome.
Also imagine a line that runs from the distance zone, through the "progressive" junk, then to the reading, across to the junk on the other side, and back to the distance. In a free-form lens with a backside add we start with a steep concave for the distance, go moderate concave for the progressive area and have a flatter concave for the reading (all concave). In a standard add on the front we start with a convex curve for the distance, through the progressive zone junk it turns to steep concave, and then back to steep convex for the reading, steep concave again, then back to convex (convex, steep concave, steep convex, steep concave, convex). In a front side add lens you end up with focal points scattered over a wider area than a backside Free-form lens. Although a backside add won't eliminate distortion, it lowers the potential total distortion because it keeps the progressive curve closer to the corrective curves of the RX, by definition thats less distortion.
We use the Nulux EP from Hoya mostly and four times out of five, if not more, the patient will describe their vision as the best they have ever had.
They also love the fact that the Bi-Asphericity of the lenses greatly reduces the minification/magnification of their eyes.
It goes without saying that the Zeiss Individual SV achieves high patient satisfaction as well.
I only wish more patients would elect to have 'Digital' single vision lenses.
I wear the Hoya Nulux EP 1.70 with Super Hi Vision A/R and love them! I'm give or take about a
-5.00 in each eye.
~ Erin
ABOC
I wish we could still get 1.70 here in the UK. Fantastic material, but Hoya have discontinued it.
The only downside of it from my experience is that it tends to discolour quite quickly.
Last edited by Robert_S; 06-05-2012 at 11:26 AM.
It's still available from Tokai and Vision-ease
Thanks Jacqui!
i have never prescribe any freeform SV. may i know usually what prescription you will prescribe that? as i seeing mostly are for high prescription? how about low prescription such as -1.00DS?
thanks..
Yeap
1.00DS....no; unless it is to put this lens on a non-standard curve to be a soecific frame. Sometimes I will when trans is added, since i can source a FFSV with AR & trans for similar money than stk
B
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.
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
Interestingly, Darryl has pointed out that as the index goes up (higher), the appropriate true form curve needs to be STEEPER...something counterintuitive to me at first.
With this in mind, it's obvious why stk, non-aspheric poly SV has had such a bad rap for peripheral vision.
B
That's very counterintuitive. Do you have a link?
Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA
“As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein
No link. Part of a discussion I engaged in with Darryl regarding this very point.
B
I think the FFSV upgrade difference is superior to a 0.25D sphere or cyl change, definitely
Last edited by Barry Santini; 06-22-2012 at 03:26 PM.
I would agree with that. It's probably worth some axis inaccuracy as well!
I'm getting very frustrated with our optometrist telling people they don't need new glasses, as if the only way to improve someone's vision is with an Rx change!
Thanks for the good advice. i may consider it as upgrade for my patient.
by the way, is Hoya Nulux EP also an FFSV? i thought is just a double aspherical stock lenses?
No. It appears in the catalogue as a stock product, but you will find the surfaced price is identical (unless you have different discounts for surfaced products), because it is a free-form surfaced lens, even if you order it as stock.
Here's what you should tell the patient they are getting if you are dispensing Nulux EP:
1) The sharpest vision possible through the centre of the lens.
2) Excellent vision from edge to edge (the best peripheral vision).
3) The flattest, and usually thinnest prescription lens available (assuming you use the correct material).
4) Improved cosmetic appearance; less magnification/demagnification of objects through the lens, particularly the patient's eyes.
5) A Hoya coating (a choice of Super HiVision or HiVision Longlife) -Hoya make the best coatings in the world. I usually tell the patients about their premium AR whilst I'm writing out the order.
With all that, I don't know how some of them say no! Unfortunately some will, but the ones who invest in the lenses will be very impressed. Remember to only dispense it if the prescription is one that will benefit, as Barry and I discussed above.
PS. Sorry for sounding like I work for Hoya. I use the Zeiss Individual SV as well, and it's a great lens.
Last edited by Robert_S; 06-25-2012 at 04:10 PM. Reason: Grammar.
HI Robert, great info you have it here.. honestly i prefer zeiss lenses for myself..
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