GSLS Part 2... Technology, terminology, and the diameter debates

Posted by Rebecca Petris on

1. Technology and the scleral lens practice

Dr Tom Arnold

This was a fun session. Dr Arnold was totally unfazed by a series of rolling A/V failures, and entertained us all by lip-syncing to the speaker in another room whose talk was being rather noisily piped into our room for while. Sadly, the other speaker will never know how many of us raised our hands when asked if we have a corneal topographer in our practice.

This is the time of day when it's getting really hard to read my notes from nine in the morning and remember what I meant and which things mattered to me and why, especially without either fresh coffee or old scotch.

I forgot to put this in my notes but I remembered later that Dr Arnold showed a video circa, maybe, 1940, with someone taking a mold of a patient's eye, creating a scleral lens and putting it on the patient's eye - all that to show that while mold-based EyePrintPro technology (incidentally, this is what I currently wear) is wonderful, the concept is old, not new. Just a whole heck of a lot safer and more comfortable... the corneas under those ancient lenses would have been gasping for oxygen before the poor actress got back to her dressing room. But hey, even the most expensive only cost $75... in... "then" dollars.

We learned how the limbus (that's the transition zone between the cornea and the sclera) resembles a pringle potato chip. (I'm familiar with pringles... I question the potato content though.) That's probably not the most important take-home point.

For some of you who have struggled with a fit after repeated efforts, I sometimes wonder how long you've had your lenses in when you're being seen (I bring this up occasionally in the group).

Dr Arnold mentioned some numbers that help explain this to me - how the clearance of the lens over the central cornea decreases after putting in the lenses: 50% within 45 minutes, 75% in 2 hours. On that basis, he recommends in some cases (especially with patients who have driven a long way) to keep them there for quite awhile or have them come back after lunch so as to observe the lenses, as otherwise this is a common reason that lenses which look great when fitted might not look so great 2 weeks later when the patient comes in having worn them for a few hours already that day.

Dr Arnold went over a lot of scanning technologies and their relative potential roles in a scleral lens practice, but not necessarily anything particularly of interest to us patients... OCT, topographers, tomographers, placido disc topography, Scheimpflug camera, scleral profilometry....

My ears pricked up at the mention of emerging technologies, such as 3D printing (Johnson & Johnson mentioned two years ago but not since), a "young guy in New Zealand" 3D printing soft polarized lenses that help epileptics, and emerging drug delivery contact lens technologies smart enough to change color to show when they're working.

Also in emerging technologies, the future of presbyopia treatment... eyedrops? Google PRX-100 and EVO-6 (Novartis) if interested in learning more (two different things with different mechanisms of action).

Then we saw some pictures of nonstandard lens insertion (or, as I've been learning the new de rigeur lingo to be, lens application). Dalsey (See Green) of course, but also two new funky looking things whose names I always forget (I got samples, couldn't get them to work for me personally but I keep meaning to get pix and blog about them). 

Finally, we got to see some clever Texas innovations such as the "Truck Stop Inserter" (a DMV Scleral Cup stuck in an inverted Dixie cup), and a couple of other items we all correctly guessed to be wire nuts, inverted. I'm not necessarily going to recommend the latter for anyone's $4,000 EPP lens, but, well, something for everyone!

[gripe] Hotel rooms have dim lighting and drive me nuts. When you have flat, very, very spherically aberrated corneas with off-the-chart contrast sensitivity loss, dim lights are torture. Oh for a brightly lit room.[/gripe]

2. What's in a name: Scleral lens terminology updates

Dr Langis Michaud et al

Oops, I didn't jot down the other name and it wasn't in the program. Sorry.

The Scleral Lens Education Society has been hard at work on a project to standardize language for all technical things related to scleral lenses. The reasons for this are quite compelling and they really do have direct implications for us patients who may be struggling with successful fit of one brand lens and need to move to another but... perhaps the two manufacturers don't use the same terms nor provide the same data about their lenses. It's great that the SLES are working to raise the pressure for standardization - the manufacturers should be in the business of making it easier, not harder, for doctors to help US. 

Most of this was very technical, but I'll pass along a few things:

We no longer INSERT lenses, we APPLY them. Gulp. I get it, and I agree, but at the same time, I'm not really ready to give up the vernacular. It's almost like asking me to say "dysfunctional tear film" instead of "dry eye", y'know? Ah well. I shall try to be good in print, in formal things, but no promises for what I say on the phone or in a Facebook group. 

Just call them scleral lenses: They want to do away with terms like "mini scleral" or "large scleral". The reasons make perfect sense. Size is relative anyway - what is a mini or a large lens depends whether you have an average cornea - and I've always found the differences in naming conventions people use for sclerals intensely frustrating. When people say "scleral" or "mini scleral" it never conveys anything to me anyway until I know the diameter. But then we're back to relativity.

Where does it land? I appreciated that they emphasized the distinction between the full diameter - as in, edge to edge - versus the "primary functional lens diameter", as in, if it lands on the conjunctiva at 15mm, but is 18mm total width, the 18mm part can be a little misleading unless you define your terms very carefully.

How thick is it, really? Lens thickness has implications for oxygen transmissibility, which is a very important safety issue for scleral lens patients, so they were making the distinction between maximal edge thickness versus maximal central thickness.

Anyway, the bottom line here is they want standardization of terms amongst practitioners, manufacturers and researchers, so that we can compare things apples to apples. Makes sense to me.

3. The Diameter Debate: Mini scleral and large scleral pros and cons

Dr Lynette Johns, Dr Stephanie Woo

Oooooh this was so fun and oooooh I was so thrilled to see Dr Johns for the first time in forever. Lynette Johns and Perry Rosenthal were my dream team back in 2006 at BostonSight. That was a simply unforgettable era to anyone who visited BostonSight during that period. 

Dr Johns argues for large (that is, relatively large!)

So as discussed in the sizing terminology class, size is relative and there is no such thing as "mini". It's not about diameter, it's all about where the lens rests. 

Dr Johns played an old movie too... but a different clip than Dr Arnold's. It was were SO SCARY LOOKING, belying the enormous smile superglued to the actress's face. Dr Johns' version showed them inserting (oops, I mean "applying") this quarter-sized, huge, thick lens, PERFECTLY DRY, to this lady's eye, and this consummate actress gazes at the camera in utter delight.

Anyway, all that just to underscore that they started big in the old days, and these days even though "mainstream" practices by-and-large (as attested by a poll done during the class) are geared towards smaller lenses, they are creeping larger again. 

Dr. Johns' presentation was pretty technical but the simple bottom line of one of her key points about size is this, and I believe it was directly mostly at keratocones (ectatic corneas): In a smaller lens, all of the "weight" of the lens rests in one spot - where that lens edge rests. She describes it as a harsh, elbow-like junction - while in comparison, in a larger diameter design, the resting edge of the lens gradually "inclines up". She showed several clinical examples of how smaller lenses may be producing compression on the cornea. So basically the benefit of the larger lens is the idea that it produces a more effective bridge over the limbus (transition outer part of the cornea). 

Another example she gave of the benefit of larger lenses was in Salzmanns Nodular Degeneration.

A second argument for larger lenses was for increased ocular surface protection, for patients where the reason for the lenses is severe dry eye. 

On the other hand, she mentioned she would prefer smaller lenses for patients with pinguecula and a few other cases.

At the end of the day, though, the message is that lens size is patient specific, and relative to corneal diameter.

Stephanie Woo argues for smaller

Dr Woo shared the results of the poll taken during the class, with 62% saying they fit mostly 16.0mm or smaller, and 37% fitting mostly lenses larger than 16mm.

She quoted Dr Michaud who says, "Why shoot a mosquito with a Bazooka?" and encouraged using the lowest risk lens for the patient. 

Dr Woo walked us through many examples of newer types of "normal" candidates for scleral lenses - that is, while in the past sclerals were mostly for people with advanced diseases, we're moving toward "normals" now, including:

  • People with very high prescriptions (for example who have never seen all that well with contacts or glasses)
  • People currently wearing RGPs or piggybacks
  • Aphakic patients (again, who don't see well with soft lenses or glasses)
  • People who have dry eye and normally wear soft lenses but are having issues
  • Unhappy soft toric wearers
  • Teenagers, including athletes - those who really value the best vision they can get

She mentioned some advantages of the smaller lenses including easier handling, less likely to get the lens decentered, and better peripheral edge alignment. Disadvantages of larger lenses were felt to include the "suction" effect and oxygen delivery concerns.

At the end of the day though they both agree that we need both smaller and larger lenses depending on individual patient needs.

Next up: Sponsored session about BostonSightScleral during our lunch break


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