Frame Question

[Kinnick]

I had a lady come in the other day with the following RX for glasses; OD -14.00 with a plus 2.75 cyl, OS -12.00 plus 2.75 cyl and a diagnosis of keratoconus from her MD. She wants to be fitted in FT28 bifocal as thin as possible, no progressive which she was a non-adapt. I recommended a Hyper Index 1.66 in a FT 28, with an AR Coat, and roll & polish the edges. She declined the AR coat due to cost. The main ? I have is what type of frame to put her in. One person thought a semi-rimless would be good and others think only a full frame would hold the lenses properly. Also some specific brand names of frames would be nice. She wants to stay in the $85.00 to $115.00 range for a frame. Thanks WCH

[Diane]

Originally posted by Kinnick:
I had a lady come in the other day with the following RX for glasses; OD -14.00 with a plus 2.75 cyl, OS -12.00 plus 2.75 cyl and a diagnosis of keratoconus from her MD. She wants to be fitted in FT28 bifocal as thin as possible, no progressive which she was a non-adapt. I recommended a Hyper Index 1.66 in a FT 28, with an AR Coat, and roll & polish the edges. She declined the AR coat due to cost. The main ? I have is what type of frame to put her in. One person thought a semi-rimless would be good and others think only a full frame would hold the lenses properly. Also some specific brand names of frames would be nice. She wants to stay in the $85.00 to $115.00 range for a frame. Thanks WCH

Curious as to why the spectacles with this Rx. What will be her best V/A with this Rx in glasses? Contact Lenses are usually the best option for this type of patient. Cost could be a factor, but how much visual acuity will she be sacrificing?

Diane

[Kinnick]

She wore RGP's for many years and can no longer tolerate them. ( She is 58). She is a possible candidate for a corneal transplant due to her kerataconus. Her ophthalmologist gave her 50/50 odds of success. WCH

[Jo]

What is her PD?

[chip anderson]

She needs a better contact lens fitter that can fit her with lenses she can tolerate. Don't believe in "contact lens intolerance".

There are just contact lens sellers and then there are skilled fitters. Cone patients can never be satisfactorily fitted with spectacles once they get past the early stages..


Chip "I can fit anything that ain't rotting" Anderson

[Kinnick]

She refuses to go back to contact lenses, so it is not an option. Can't make somebody do something they don't want to do.

[Jeff Trail]

First thing I would do is stay AWAY from a rimless mounting :)..second thing is do NOT roll and polish a that high of a minus because the lens will act like a prism and scatter light through out the lens....
As for a frame? Well the rounder the better (no sharp corners) also the frame that will give you the LEAST amount of decentration (none would be best :)) Have the lab cut the lens ON center..do not use prism rings for decentration.
Also do not confuse a smaller "B" but oblong shaped frame as being an advantage.. lens are figured from the furthest points to get it to cut out, I can't tell you the amount of times I get a 58 eye with a 35 B and they can't figure out why it was not thinner :rolleyes:
I'm trying to think of the name of the frame (on the tip of my tongue) it has off set temples from the actual mounting so it fits likes a larger eye size but the actual "frame" (lens size) is only a 48 or so..I'm thinking it was either MODO or a Lux. frame...they work great for these high minus jobs.
You may also want to check into getting a bi-concave cut.. a couple companies make a molded bi-concave in FT's.. as long as you do not carry more than a -2 or so on the front surface then they will never have that much of an effect on the optics.
Good choice on index..No-No on the R&P, get the least amount of dec., cut the lens on center..and make sure you fit it on a mono PD even though it is a FT. ..last but not least rounder the better ..
That's about all I can think of anyone else? ..by the way what's her best CVA?

Jeff "love low vision..I do enough of it" Trail

[Sara]

Uncle Chip & Jeff,
How about using reverse geometry CL(orthokeratology) or combination of RGP lenses & spectacles? Also vision in each eye is missing,not mentioned here.Normally keratoconus patients have irregular astigmatism and poor vision.
Sara
Student

[This message has been edited by Sara (edited 03-09-2001).]

[ziggy]

I just fit a young lady the other day with nearly the same Rx.
-14.50+1.75od -13.50+1.50os
We used a poly lens and a frame that allowed 0 decentration. I agree with Jeff about not polishing the edges. good luck!!

[chip anderson]

Sara: Reverse Geometry works well on transplants, not cones. The reason I suggest (insist) rigid lenses are the only modality for cones, is the tear layer beneath the lens pretty well takes care of the irregular astigmatism. No forward lens can, even if you could grind it, they would have to look through only one spot.

Do not try to re-shape cones with flat lenses, you will get central scarring much more rapidly than if fit with an apical brush (apical brush= very faint flourcein clearance right after blink, fading just before blink.

Chip

[This message has been edited by chip anderson (edited 03-09-2001).]

[Diane]

I suppose that I still believe that the patient is entitled to the best vision possible, which she will be sacrificing with spectacles.

A lot of patients are managed very nicely with piggy back lenses, which uses a soft lens and a rigid lens. Gives comfort with the quality of vision of a rigid lens.

I know your question is on frames, but I believe good V/A is paramount.

Diane

[Homer]

Thank you Jeff for advising against roll and polish - even if one should decide to roll the edges for some reason that I have never yet figured out.

I have never understood why one would polish the edges of an A/R coated lens - the whole point of A/R is to reduce "visual static" from light bouncing around in and off the lens .... and then we open up the edge by polishing it? Duh!?

[Jo]

Jeff:

Modo does make a small round. I am not sure who makes them but there is also a line of frames called Minimizers. I brought up the PD here because small and round is the right shape but many of those styles have large bridges. If the patient has a narrow PD a frame with a 22mm DBL wont give the results a frame with a 17mm DBL will.

[Darryl Meister]

I have seen a lot of good tips on frame selection for high myopes in this thread. Here are a couple more that might prove worthwhile:

Use a frame with a substantial rim. This well help conceal the <thick> edge of the lens and also provide a more secure mounting.

A frame that holds its adjustment is also a good idea. After all, even small shifts in the fit of the eyewear can affect optical performance for high-powered lenses.

To achieve a wider frame fit, use a wider bridge (DBL) size and smaller eyesizes. This will help minimize lens thickness, particularly in the nasal region. (Anyone who has ever attempted to adjust nose pad guard arms around the thick nasal edges of minus lenses can relate to this one.)

Good centration is an obvious necessity. Frames that keep the eyes well-centered will perform better optically and minimize the required decentration (and accompanying thickness).

As Jeff pointed out, round and oval frames are also preferable. However, I'm not against a good bevel treatment -- such as rolling the edge (polish or not).

Best regards,
Darryl

[Jo]

Darryl:

Optima makes back aspherics.; however, I am not sure on their ranges. What are your feelings on that type of lens?

[Kinnick]

Well, this person came in on my day off and the optician fit her in Brooks Bros 189 full frame, not round, but not oblong either. The lenses are a Hyper Index FT28 with A/R coat and rolled & polished lenses. Her PD was 31.5 and 30.5 monocular. Frame eye size is 50 with dbl at 19. She felt a round lens would be wrong for this person as she felt that she had too much cyl to make it work. One thing I'm learning is that no one can really agree on things in this industry. Oh well at least I'm learning.

[Darryl Meister]

Originally posted by Kinnick:
She felt a round lens would be wrong for this person as she felt that she had too much cyl to make it work. One thing I'm learning is that no one can really agree on things in this industry.

Hi Kinnick,

I didn't catch the axes of the cyl corrections, but I am curious at to why your optician would suggest that a round frame wouldn't work with cylinder power? Cylinder power adds edge thickness to the lens just like minus power, so its thickness would also be reduced with smaller eyesizes and round/oval styles. Conversely, the edge thickness produced by cylinder power can also be exacerbated by poor frame choices. In some cases, depending upon the cyl axis (particularly at axis 180), oval styles might be more preferable. An oval style, with its narrower B dimension, will reduce the excess thickness at the top and bottom edges of the lens produced by a minus cyl at axis 180.

Yes, opinions vary a lot in this industry -- as in many, I suspect. If someone makes a statement or argument that you are unsure of, or that is in contradication of something that you currently believe, my advice would be simply to ask him/her to describe the reasoning that supports the statement. Any contention that is not founded on sound reasoning, a logical rationale, or supportable premises, is just speculation and conjecture. At least that's what they said in school! ;)

Best regards,
Darryl

[Darryl Meister]

Originally posted by Jo:
Darryl:

Optima makes back aspherics.; however, I am not sure on their ranges. What are your feelings on that type of lens?

Hi Jo,

I think backside aspherics are great lenses. Although backside aspherics may not perform much better optically than frontside aspherics, they often produce thinner edges in minus powers. (When asphericity is applied to the strongest surface of the lens, it is possible to make the lens a bit thinner than a lens with asphericity on the weaker surface. For minus lenses, the strongest surface is generally on the back.)

However, I would recommend using backside "atorics," which are lenses with a unique amount of backside asphericity applied to each meridian of the surface. Atorics provide better optics in lenses with cylinder power -- which account for the vast majority of Rx's out there (about 70%). An atoric lens series and a well-designed aspheric lens will work about the same in sphere powers. SOLA, my employer, makes a line of completely atoric 1.66 high-index lenses called ViZio. Additionally, Optima makes some of their lenses in atoric form in some of the high-minus/high-cyl powers.

Best regards,
Darryl

[shanbaum]

Originally posted by Darryl Meister:
Hi Kinnick,

I didn't catch the axes of the cyl corrections, but I am curious at to why your optician would suggest that a round frame wouldn't work with cylinder power?

I'd guess, because of the greater potential for the lens to be rotated off-axis.

Of course, it's also easier to rotate the lens to the correct axis, if there's not too much decentration - which could induce prism.

[Darryl Meister]

Hi Robert,

That's an excellent point about cyls in "perfectly" round frames... However, very few frames are made that way (i.e., circular) for that very reason. Perhaps "rounded" or "more rounded" frame styles (as many today currently are) would have been a more appropriate term to use. This would include ovaline styles, P3, perimetric, rounded rectangles, ovals, etcetera.

Best regards,
Darryl

[Kinnick]

To answer the question on what her BCVA was, I looked at the prescription she brought from her Ophthalmologist and it was not written on there. That group rarely writes those out for any other office, but it would be interesting to know especially if the RX doesn't work well for her.

[Darryl Meister]

Actually, now that I think about it, "rounded" may not be an adequate term either. The important factors are to minimize the effective diameter and to not have corners.

Best regards,
Darryl

[This message has been edited by Darryl Meister (edited 03-13-2001).]

[LENNY]

Why double concave lens will make th rX thinner?
Asphericity?

[chip anderson]

Lenny: I am no sure double concave makes the lens that much thinner, but it does keep the posterior (the true base) curve from having to be so steep on extreme minus powers. Steep bases induce peripheral distortions and other optical problems and once they get beyond a certain steepness one can see only though a tiny area in the center.

[Jo]

Not that you would use it in this case but is a myodisk only available in SV?

[Jeff Trail]

Chip&Lenny,

Actually a bi-concave would not really be that bad of a choice, depending on what they had before (say they were wearing a CR39) the peripheral was already wasted optics before.. since even on a plano base curve you would end up with something like a -12/-14.75 curve..I think the RX was a -12 -2.75 cyl... well you see my point.. now going to a high index of 1.60 bi-concave FT you have a choice of caring a -6 or -4 on the front surface ... so between the index and the front curve you can actually take off about 5.5 or so ^ of ocular curve!! :) .. and by using a -4 front the amount of loss in peripheral would not really be that great.. I can work out the mat but it would be around only 4% of the visual field..that's not bad for someone that is used to having a narrow visual field to begin with..
I would really push the AR coating though if you went bi-concave. ..sometimes the biggest culprit is the reflections on the seg line in these types of cuts and that coating will help greatly there.

Jeff "I hate to see people with these problems but I do love to do low vision work" Trail

[Alan W]

Jeff
Although it's been a very long time since I've done this, my sense is that a lenticular minus might also be an option. Unless I missed that being brought up for discussion. Would not such a configuration, if the calcs are run to select the right plus curves achieve a decent lens?

[Alan W]

Jeff . . .
Cancel that. I just realized there's a FT 28 involved here. I couldn't handle the brain damage!
How 'bout single vision for PR and a nice library of Talking Books for this patient?

Thanks,
Alan

[Darryl Meister]

Originally posted by Alan W:
Jeff
Although it's been a very long time since I've done this, my sense is that a lenticular minus might also be an option.

On a flat-top, I believe that you could still use a minus lenticular if the lens had little or no cylinder. You would get a flat (0.50) base curve and grind the convex carrier curve and optical zone (or aperture) with the prescribed power on the back. However, if you grind significant cylinder power on the carrier curve (back) surface, your bowl will be very elliptical in shape -- and not circular. These generally take quite a bit of skill to do right, though. The pre-made Younger blended Myodisc is a better option for single vision powers.

Best regards,
Darryl