hello,

i have been wearing RGP CL's for about 6 months now and they greatly reduce the horrible aberrations caused by my lasik surgery.

there are a few issues, however. the lenses seem to fit well, but they wobble, which i understand is normal. when my pupils are at normal dilation, which is a bit large, i can see the edges of the lenses, especially on the side opposite my nose, and they produce a kind of watery streaking of light. no where near as bad as the nightmare of lasik-induced aberrations but still there and rather bothersome.

also, and it may seem strange - when i only have one lens in it seems to wobble less than when i have them both in.

are there any refinements in order or are they as good as they're gonna get?

thank you.

Ideally the lenses should not move excessively. Movement depends on the design and the overall diameter of the lenses. What you are seeing is probably not the edge of the lenses but glare associated with poor positioning.

Do you happen to know the overall diameter of the lenses and the optic zone diameter?

This message has been edited. Last edited by: Dr. DavOD Hartzok,

OZ diameter = 8.4 mm
Lens diameter = 10.0 mm

helm1t

Post-ablation RGPs with an OZ of 8.4 mm will generally vault the ablation zone since the ablation zone is smaller. The resultant "steep" fit across the ablation zone tends to de-stabilize the lens positioning. This can reduce the quality of vision and give you the sense of seeing the lens edges.

Post-ablation fitting, IME, requires a larger overall diameter. A larger, say 11.0 mm lens diameter, provides for a secondary and tertiary curve to be the "fitting" curves, provided the optic zone is made to more closely approximate the diameter and curvature of the ablation zone. What most fitters do not recognize is that the secondary and even tertiary curves - because they are being "covered" by the anterior curve - actually are part of the lens optics. In other words, the fitting curves correct a lot of the spherical aberrations present after RS. It is not the "optic zone" alone that is providing correction.

Relatively big OZs on a virgin cornea can be okay but on ablated eyes, the benefit of large OZs is offset by mechanical fit issues. Without the mechanical fit, comfort, lens stability and vision are not optimized. I typically use a 6.5 mm OZ, a 1.0 mm secondary and 1.0 mm tertiary curve width on myopic ablations.

helm1t,

The corneal lens that you are wearing is likely a bit too small in diameter which is why you are reporting the "wobble" or instability. There just isn't enough "normal" cornea for a lens that size to have enough of a "footing" to keep it stable. In my experience with post-rs irregular corneas, the irregularities present throughout the central treatment area will give way to a more normal, untreated and unaffected area out nearer the limbus. The more normal area out there can be used to properly "foot" the lens so that there is increased stability. If an average cornea is ~ 11.7 mm, you have approximately 1.5 mm more of cornea (the lens cannot sit on the limbus so I am subtracting out 0.2 mm for this) that can be used to aid in fitting the lens. This represents an increased fitting area by a little more than 32% to aid in stabilizing the lens. The problem however is getting the lens to fit properly in this far periphery of the cornea (in addition to still accommodating the central irregular area). This peripheral area is typically is flattening (from central to periphery) at a quicker rate which creates more problems in getting a traditional design gas permeable lens to accommodate. If the fitting in this area can be done in such a way as to create an alignment relationship between the back surface of the lens and the front surface of your cornea, you will not only improve the wobble and the comfort, but there is also a good chance that you will improve the quality of your vision with the lens as well.

I hope this information helps and I wish you all the best of luck.
Sincerely,
Dr. Maller

what my optometrist said in response to your reply, Dr. Hartzok:

quote:

I think he has some valid points however, I don't believe many people will experience good comfort with a rigid lens of the size he is suggesting.

Helmit

Perhaps your OD is unfamiliar with the fitting techniques that make a larger lens comfortable? Most post-RS patients benefit from a larger lens (even as large as the Macrolens— which is much larger than a typical corneal lens).

The comfort depends on the expert fitting of the secondary and tertiary curves, and unless the fitter is familiar with the complex relationships between these curves and the optics involved, the lens will not be comfortable or provide clear vision.

Both Dr. Maller and Dr. Hartzok and many others routinely fit larger lenses that provide clear vision with great comfort.

seeing my optometrist he said he thought a wider diameter lens would touch my eyelids more, making it less comfortable.

he did not comment on the ablation zone/lens "OZ" issue but said that the lenses are producing an "even tear layer" or something underneath and because of that he would not recommend changing anything. he did have to work with someone from the CL vendor to design even these lenses. he described it as an "excellent" fit.

The majority of RGPs are "designed" by someone at a lab which is why so many people have problems wearing lenses. We now have patients whose corneas have been altered beyond anything that ever occurs in nature but we still have Bob or Susie at the CL lab designing lenses.

Most labs do not understand what is required. I get responses like, "Well, golly, we've never made lenses like what you want. Shucks. And you say you've done something like this before? I dunno. We've been in business a long time and this is a horse of a different color. This isn't how we design lenses."

This is why the RGP business is going down the tubes and why it is a difficult process to put together a network of RGP "fitters" (i.e, doctors who really understand the process). This is also why we need to use the term "corneal prostheses" when referring to post-RS RGPs. There has to be a paradigm shift in ODs' thinking when caring for patients with ablated corneas. This is not taught in Contact Lenses 101.

figures.

helm1t,

Most ODs are well-intentioned and recognize the troubling situation some RS patients are forced to deal with. CL labs have developed "reverse geometry" lenses in response. However, normal geometry and reverse geometry are on a continuum. Some post-RS patients need very little "reverse" effect; some need none or can even get by with normal geometry. It all depends on the original (pre-surgery) corneal shape and how much that original shape has been modified. The greater the degree of ablation, the more likely a reverse geometry configuration will be needed. So, the degree of "reverse", the difference between the central curvature and peripheral corneas carry individual characteristics. You and your neighbor could both have been -6.00 nearsighted prior to surgery, both of you may have ended up Plano (no correction), but you both need differently shaped RGPs to regain your vision and to be able to wear your CLs comfortably. The lenses have to be customized to you, fitted to you, instead of expecting YOU to fit into some pre-determined, reverse geometry lens. The peripheral curves have to fit as precisely as the central curves.

In almost all instances of standard RGP fitting, only three parameters are written into the RX: the overall diameter, the power, the base curve (curve of the lens center) and maybe the optic zone diameter. The peripheral curves are generally unknown AND, for some companies, a proprietary matter, meaning the labs don't like to tell what those curves are. But these curves have to be "fitted", particularly on large corneal lenses (>11.0 mm). Also, most labs don't really know what curves to use on these larger lenses (as a stock item). Peripheral curves on standard lenses usually vary with the base curve. But, after RS, there is no correlation between the required central curve (it was modified by the surgery!) and the peripheral curves. This is why we can't use stock peripheral curves. My old analogy of a size 8 foot, in human form it can only be just so wide and the heel is more narrow - well, what if the heel was WIDER than the ball of the foot? You're not going to find shoes for such a foot at Foot Locker because they are certainly not what nature normally provides. You would have to have custom shoes.

quote:

It all depends on the original (pre-surgery) corneal shape and how much that original shape has been modified.

that reminds me - as my initial surgery was 8 years ago i don't think i can get color corneal topographies taken before surgery - b/w but not color - will that matter in the design of the custom rgp cl's?

helm1t,

Corneal topographies do not accurately depict the peripheral corneal profile for RGPs in the 11.0 mm diameter range. The pre-op topos are good for determining if there were corneal irregularities prior to surgery. After surgery, irregularities are, well, the reason the patient is being fitted with RGPs. Post-surgical topos of the ablation zone usually show some irregularities which are, hopefully, going to be smoothed by the central lens curve (this applies primarily to myopic ablations). The secondary or transitional curve is relative to the central and peripheral RGP curves, so post-op topos don't have a lot of significance in the actual lens design. I need to see/do post-op topos to give some idea of difficulty in getting the lens alignment I want to see, but I don't depend specifically on those topo values.

This message has been edited. Last edited by: Dr. DavOD Hartzok,

Some success people!

I am posting in completely the wrong place but I wanted to post this message before the end of the day and for some reason I can never get to the right place on this board.

Well after reading all the negative stuff regarding wavefront glasses on this board I decided I had to find out for myself. The cost was marginally more than the usual cost of glasses and with the constant pain I was in probably caused by never ending visual strain and the wondering how I was going to survive another day at work 13 years on, it had got to be worth a whirl.

There is only one dispensing optician for wavefront spectacles in the UK and he would have to be the opposite end of the country. But 2 days after receiving the glasses it was well worth the visit!

I guess he could read the scepticism in my face and the heard it all before look when he even started to 'big up' the technology. However even though the diagnostic machinery decided I would not be a good case, as I had very high amounts of high order visual aberrations (you dont say!) he assured me he could 'fine tune' things for me and get an 80 percent improvement from my current vision. And stone the crows that is exactly what I would say I have got, and even better I can live with it - its took me from the edge back into a world were I dont mind getting up in the morning.

This optician told me he had turned people away - if he knew he could not help them and only the week previously he had done so.

As Its been pointed out several times on this website - I dont expect this is the answer for all. I can only tell you that most of my problems seem to stem from not being able to see well enough in anything but the brightest artificial lighting. However I dont seem to have the night driving issues that some have.

To see the difference I put on my old spectacles and observed 'written material' in a darkened room - I found I could not really make anything out. When I put the ophonthonix glasses on I found I there was a very notable improvement.

Like I say I can sense and feel this is not the wonderful refraction corrected vision that I was robbed of over a decade ago - but it is a damn sight better than it was a week ago, before Id gotten these glasses.

Another thing, you can detect when your eyes are moving out of the best corrected zone but it is still better than it was.

I still want to continue with contact lenses to see if I can get along with these to. The vision is not quite as crisp as I know I can get from a lens.

One last thing dont think for a minute I am on this site helping anyones marketing pitch - not after what I have been through!


If anyone wants any more info let me know
Debbie(UK)

Debbie,

Anything that helps you is worth reporting. While most of those I hear from feel they wasted their money, it is always possible that I'm NOT hearing from the happy campers. Depending on the kind of aberrations one has, different things may work. It's good to know that something has provided you with much desired relief.

I wonder if because you don't have the night vision disturbances that has something to do with the Izon lenses being more effective for you.

I have been unable to find any further information regarding the TRIPLA XL lens. If anyone has heard of this lens or knows anything about it, please post it here, or email me at info@visionsurgeryrehab.com and let me know where to find details. It may be that something was lost in translating the name, as the patient was treated in Belgium, and English is not his first language.

Getting back to my posted topic - say I obtain a pair of RGP CLs that fit. How hard will it be to get a new pair every year or two when I need one? Is it as easy as sending the vendor the spec sheet? Thank you.

Yes.