8 Base frame & Rx question

[snowmonster]

I've been to Darryl's website at Opticampus.com and used the wrap frame calculator, but I don't understand how you measure degree of wrap in a frame.

I've got a Columbia Blackjack (nylon groove) with a -2.00 -0.75 x 094 in Polarized Grey C CR 39 which has 8 Base demo lenses. We're planning on using 6 Base to limit adaptation issues.

Can anyone give me a rough idea about degree of wrap?

Thanks!

-Steve

[HarryChiling]

The way I do it is to hold the frame flat against an edge then mark the center of the bridge and the edge of the other lens. Now this angle could be measured with a protractor or by using the tan of the angle and measureing. This angle should be divide by 2 to split the wrap between both lenses. you could also have the patient wear the frame and look at you staright on and mark the lens at that position, then turn their head so that the lens is perpendicular to your gaze and mark the lens again. Given that the average distance from center of rotation of the eye is 27mm the tan of the angle of wrap would be:

tan(angle)=measure of the two marks/27mm

[Cherry Optical]

I've been to Darryl's website at Opticampus.com and used the wrap frame calculator, but I don't understand how you measure degree of wrap in a frame.

I've got a Columbia Blackjack (nylon groove) with a -2.00 -0.75 x 094 in Polarized Grey C CR 39 which has 8 Base demo lenses. We're planning on using 6 Base to limit adaptation issues.

Can anyone give me a rough idea about degree of wrap?

Thanks!

-Steve

I believe there is a chart on the board somewhere that will allow you to lay your frame down and get a measure. I made a sheet that all of our CS reps have at their desk to use for wrap frames.

Darryl's program rules. We process approximately 15 wraps per week with little to no optical problems. Learning the techniques needed to edge and mount each frame is another issue.

Adam

[Fezz]

This may lead you to the chart you need.

Optical File Directory Forum
There is a face wrap article there.

[Audiyoda]

Okay, call me a knuckhead, but why not use the KBco SV-Wrap?

[Darryl Meister]

As Fezz mentioned, I made a basic frame protractor that you can print out.

[jofelk]

As Fezz mentioned, I made a basic frame protractor that you can print out.

I am not able to view the page ?

jofelk, you do not have permission to access this page. This could be due to one of several reasons:

1. Your user account may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
2. If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.

[Barry Santini]

As Fezz mentioned, I made a basic frame protractor that you can print out.

I too cannot view this link/page. What's up? BTW, through the site advising me there is a problem, doesn't help me fix it!

Barry

[Fezz]

Whew, I am glad its just not me.

But---I can access the page if I log out!!! Go figure!

[Cherry Optical]

Okay, call me a knuckhead, but why not use the KBco SV-Wrap?

I am under the understanding that if you do the tilt/wrap calucations that you don't need to use a 'special' lens for wrap frames.

We have never used the KBco SV Wrap or lenses like the Attitude from Shamir. We use the calc program, grind a lens to take into consideration the tilt/wrap/fit, etc., and apparently an optically correct lens is being produced...

Now if someone could come out with a 90 mm (extremly large) polarized lens blank... that would have some value in helping the wrap lens market.

Adam

[Audiyoda]

KBCo uses basically the same calculations: KBCo RXCalc - my point is why try to fit a 6FBC lens in a frame designed for a 8FBC lens? Most patients want a high wrap frame for the looks - then they see reality when the dispenser put a 6FBC lens in the frame - looks horrid IMO.

KBCo's lenses are aspheric and have phenominal optics - I dispensed a pair of -5.50 -1.00 OU to a patient a few weeks ago and he had no issues at all with the FBC.

I'm in no way trying to knock Darryl's program - I'm simply pointing out what I feel is a great alternative for high wrap sunglass frames.

[Barry Santini]

I am under the understanding that if you do the tilt/wrap calucations that you don't need to use a 'special' lens for wrap frames.

We have never used the KBco SV Wrap or lenses like the Attitude from Shamir. We use the calc program, grind a lens to take into consideration the tilt/wrap/fit, etc., and apparently an optically correct lens is being produced...

What I know so far on (advanced) wraps:

1. Tilt Calculator addresses *straight* ahead correction of wraps, not to the side

2. You MUST be sure RX is fully corrected for Infinty/DV...no overplus!!

3. You must make an effective PD calculation for any wrap angle over 20 degress

4. You can routinely flatten just about any wrap 1 diopter from the nominally found base curve

5. Some people just *won't* be able to wear wraps...albeit a small percentage.

6. KBco wrap, ICE TECH, Spazio, et.al, provide aspheric/atoric/truncated lenses that improve the peripheral optics (and temporal minus thickness) not optimized by the Tilt Calculator.

7. I speculate that the anecdotal reason that I (and others) are not finding that the *lack* of using the lenses mentioned in point #6 is a problem for our clients is that the "bad" (non-optimized) peripheral optics are pushed back, out of the client's primary *field of view*, by the wrap itself.
I have found this true for progressives, as well.

My two cents, what's yours?

Barry

[Robert Martellaro]

This seems to work. I hope it's OK to post it.

http://www.optiboard.com/forums/show...36&postcount=3

[Darryl Meister]

I'm in no way trying to knock Darryl's program - I'm simply pointing out what I feel is a great alternative for high wrap sunglass frames.

1. Tilt Calculator addresses *straight* ahead correction of wraps, not to the side... 6. KBco wrap, ICE TECH, Spazio, et.al, provide aspheric/atoric/truncated lenses that improve the peripheral optics (and temporal minus thickness) not optimized by the Tilt Calculator.

This is correct. My original program, and KBCo's new Rx Calc program, both compensate the prescription for lens tilt, which essentially determines the quality of vision straight ahead. However, in order to obtain a wide field of clear vision when using non-standard Base curves in these frames, you would really need to use an aspheric (or, better still, atoric) lens design.

[HarryChiling]

In some high wraps an atoric almost seems necessary. If you have ever edged a high wrap with a flat top or bottom and small B measure, you may have had issues with the high degree of wrap wanting to make the lens bulge out of the top or bow out. An atoric design would suit this best so that the 90^o meridian can can be flatter and fit better and the 180^o meridian can be more wrap and fit better.

[snowmonster]

So let's say I just surfaced this job for a left eye with 20 degrees of wrap and 10 degrees of pantoscopic tilt and entered the adjusted power of -1.80 -0.59 x 109 in my surfacing program for an original Rx of -2.00 -0.75 x 094. Again, I'm running this on a 6.25 Base.

Should I be able to read the -2.00 -0.75 x 094 anywhere on this lens (like if I measure it with the frame straight front to back as if a patient was looking forward through it vs. putting the back of the lens flat against the lensometer)?

Thanks!

-Steve

[HarryChiling]

You should be able to read the original power at the OC if you hold the lens at a 20^o wrap and 10^o panto tilt in the lensmeter.

[lensgrinder]

Should I be able to read the -2.00 -0.75 x 094 anywhere on this lens (like if I measure it with the frame straight front to back as if a patient was looking forward through it vs. putting the back of the lens flat against the lensometer)?

No. You will read the power that you surfaced. Think of it like a vertex distance compensation. Let us say that the vertex in an Rx of -10.00 will fit 3mm closer to the eye than it was refracted, you need to change the power to a -9.75 so you will surface a -9.75 and that is the power that you read in the lensmeter, however when the person looks through the glasses they see fine. You compensate the power so the person will not look through a stonger or weaker lens.

[Barry Santini]

You compensate the power so the person will not look through a stonger or weaker lens.

But you also need to keep in mind:

1. Glasses slip...including wraps
2. wrap glasses + female clients = increased VD for lash clearance
3. Myopic progression
4. 20/20 is 0.16D undercorrected for full DV usage
5. General fabrication "habit" of your lab with steeper bases + polycarbonate material
6. Ditto # 5 for Cylinder powers
7. wraps that fit close (11 VD) work best

Barry

[HarryChiling]

wraps that fit close (11 VD) work best

That is especially true with the progressives withe the key hole effect and all, but it also helps reduce the area of lens that is used there for eliminating much of the off axis aberration the patient has to look through.

[snowmonster]

So Lensgrinder says I will only read the surfaced power while HarryChiling says I should be able to read the original power.

Which is it?

Thanks.

-Steve

[HarryChiling]

Both, if you were to verify the Rx you should verify the compensated Rx by traditional methods in your lensmeter, however if you wanted to see the prescription from the patients point of view (original Rx) then hold the frame at the same angle in which the patient will be viewing it, in yu example 20^o wrap 10^o panto. I would go with what lensgrinder says, becasue he is also making sure you use your lensmeter correctly when measureing, which is measureing the comp'ed Rx, plus the if you were to measure the comp'ed Rx you get the correct reading everytime, however if you wanted to see the original Rx it would depend on if their was any comp'ed vertex distance calculations present.

[lensgrinder]

But you also need to keep in mind:

1. Glasses slip...including wraps
2. wrap glasses + female clients = increased VD for lash clearance
3. Myopic progression
4. 20/20 is 0.16D undercorrected for full DV usage
5. General fabrication "habit" of your lab and steeper bases + polycarbonate material
6. Ditto # 5 for Cylinder powers
7. wraps that fit close (11 VD) work best

Barry

Very good points. My exercise was merely and academic one though.;)

Snowmaster, as Harry has already pointed out, I am talking about putting the lens in the lensmeter with the back of the lens against the lens stop, not tilted. Just like you verify a regular pair after surfacing.

[snowmonster]

I downloaded that KBco program and it produced a bit different numbers, seems to make more sense, not as drastic of an axis change.

We'll run the official job now!

-Steve

[drk]

Good thread by good opticians.

A thought:
1.) This is all well and good for SV
2.) Intuitively, there is more that can be done on a progressive design (a la Shamir Piccolo Attitude et. al.) than distance Rx and prism compensation. What about the funky angle's effect on inset (seems like more would be needed, independent of prismatic compensation)? What about designing for less nasal "distortion" in the distance periphery? What about "respect" for the horizontal midline for primarily distance-oriented application?

Any commentary?