Caveat: Read at your own risk. I am not a doctor. Et cetera.
General Session: State of Scleral Lenses
The early days of scleral lenses (Lynette Johns)
Dr Johns presented quite an interesting history of contact lenses, crediting Tim Bowden's research - and by the way this history is covered in a chapter of the bible, I mean the book on scleral lenses that she and Melissa Barnett have recently published.
She reached all the way back into ancient Egyptian ocular prosthetics made for mummies - since prosthetics are what ultimately what scleral lenses emerged from - then then followed it all through concepts and advances from the 1500s to the present. It's really quite fascinating how far back this history reaches, including trial sets for keratoconus as far back as 1916! Even before that, in the late 1800s, they were making molds of the eye from cadavers (!) to use in making contact lenses.
How about a little history of what they used to fill scleral lenses in, say, 1900-1950? Here are some of the things that were documented in the history:
- grape sugar
- and, yes, (ugh) saliva... noting that bubbles were probably a problem!
- worst of all, apparently in a 1949 survey of 875 patients, 30% were inserting them DRY.
You might be interested to know that patients in those eras had a lot of the same issues as now, such as removing lenses to refill them.
Dr Johns noted some creative design innovations to work around things like trabeculectomy blebs (echoes of today's EPP lenses). And one of her pictures included a picture of someone using a stand that was clearly a predecessor of Dalsey Adaptives "See Green" stand.
Modern pioneers... Don Ezekiel (first to publish use of gas perm materials) in 1983. Ken Pullum (at Moorfields at the time) with PMMA lenses based on molded designs, started using gas perm materials. He describes his role as having been "in the right place at the right time, guided by a guardian angel." Dr Visser (Netherlands). "You have to use not just hands and head - you also have to use your heart." Finally, she shared about the great legacy of Perry Rosenthal.
"Scleral lens related clinical research" - Muriel Schornack (Mayo)
Oboy. This is where we started kicking into gear for an intense, information-packed day, for me, that is. I was delighted to get in a long conversation with Dr Schornack later in the day.
As Dr Schornack started introducing her talk, I appreciated her encouragement of all attendees to consider the importance of their own individual role in research, even if they weren't engaging in research to publish, and even if only the form of sharing simple anecdotals with each other: "My N of 1 [single incident that proves nothing] may make you curious about something"... that leads to research that uncovers a trend.
She mentioned studies about some innovative potential therapeutic uses of scleral lenses, including as a "ptosis crutch", drug delivery device, or to treat various conditions. She also noted that a welcome sign of increased maturity in this field is that we're starting to see prospective studies, rather than just case reports and retrospective case series.
Then she moved into data about clinicians' experiences to date with scleral lenses through surveys such as SCOPE, and she says sometimes these raise more questions than answers! But what follows was a wonderful high-level view of all the potential issues or complications that can arise that have been documented in the literature so far.
CAVEAT ON THIS SECTION: These were my notes to myself. Seriously doubting usefulness to most of my readers but I'm kind of time strapped so I'm just leaving these intact the way I wrote them at the time. For the worry-warts amongst us, either skip this section, or at least remember not to let it scare you. I think the takehome for most of us should be that the picture is NUANCED. When you read that "A study said XYZ happened..." remember that it is just a single study. It takes multiple studies that agree before we actually know whether something really is a problem, let alone WHO it's a problem for, under what circumstances or why.
- "Epithelial bogging" - noting that there inconsistent use of this term? Seems to be transient. No complications reported yet. What are the causes? Could it be related to the filling solution, or lack of interaction with the lids? (Normally the eyelid smooths epithelial cells.)
- Perilimbal epithelial bullae (Nixon et al, 2017) - 14.6mm lenses;
- Transient epithelial bullae. Gloria Chiu 2018 Dr Schornack suspects this is happening quite a bit more than we know
- Epithelial macrocysts (Nguyen et al 2018) series of 3 pts. No complications.
- Corneal edema
- Corneal neovascularization. Presented a case of a patient who used impression based lenses (aka EPP) but (OMG) put the wrong lenses in the wrong eyes over a prolonged period and developed scarring and neovascularization. "It's a good argument to keep close tabs on your patients." Also noted Cressey at al, 2018 study, reported reduction of neovascularization and opacity.
- Microbial keratitis (this is the "100 lb gorilla" to keep close tabs on incidence of). Not frequent, but there are individual case reports.
- Conjunctival injection. "Heel" or junctional compression vs "Toe" compression.
- Prolapse. She had a case, couldn't get it to go away but patient was hospitalized for other reasons and couldn't wear lenses and it resolved on its own.
- Post-lens fluid reservoir debris. See Caracedo (sp?) 2017 study - counted number of particles in photos!
- Mid-Day fogging! Skidmore et al 50% prevalence with no association between fogging and tear exchange or reservoir thickness. Pucker et al, 84.8% of practitioners reported fogging in their patients at least some of the time. Scope II also though I missed the numbers.
- Yes, scleral lenses settle over time (5 studies). Lots of questions about why, and about individual factors, lens fit / design questions, does it matter how many weeks/months they've been in lenses, etc.
- IOP: 4 studies; conflicting results, which is great because it helps refine the questions we need to ask. Noted challenges to measuring, and questions about why the results vary so much. Who are the higher risk patients? How do we mitigate the risk?
- Do corneal parameters change? Yes.
- Visual acuity? yes, lots of evidence in the literature that we can improve acuity and ocular surface disease. Some studies suggesting we can improve conditions in corneal irregularity. (note to self to fup on that)
ref. SCOPE I and SCOPE II studies....
It was at the end of this section that I really started brainstorming about patient education measures that would encourage us patients to take the follow-up appointments seriously. For many of us, that's not an issue at all, pain and issues will keep driving us back at frequent intervals. But for many other scleral lens users, if they're reasonably functional in their lenses they will not go back until they have what they perceive as a problem... in the meantime, there might be detectable signs of a problem brewing that they can't recognize on their own.
Scleral Lens Research & Technology (Stephen Vincente)
Now we started getting progressively more technical and honestly I won't make it to the other ones that I want to write up if I even attempt to truncate these notes into a user-friendly format. So I'm going to condense this one WAY down and just say:
- Hypoxia and edema are the hot-button topics. Key question is all about ensuring cornea gets enough oxygen - which is affected by many things, lens material, fit, size, design, whether there's any "tear exchange"going on after we've had our lenses in for a little while.
- Edema starts quickly and peaks about 60-90 minutes after lens application, and is taking place mostly in the corneal stroma not the epithelium. It's also resolving pretty quickly once the lenses are out - after 8 hours of wear, it's 40% gone in 5 minutes. After 2 hours of wear, it's completely resolving in 30 minutes. (That's in a 100dk lens.)
- We do not know the long term implications of low grade edema. Mental note.
- They/we have a lot to learn about what's going on in the fluid behind our lenses, and yes, it matters.
- Improving oxygen delivery isn't as obvious as you'd think. For example, a single fenestration (making a little hole in the lens) doesn't actually help.
- To a point you can keep improving the oxygen transmissibility of the lens material but... then it plateaus. (But then... possibly before it gets that good anyway, the lens is too easily damaged to be useful...)
- We do not know, but need to know, the safety thresholds for scleral lens user for "compromised" eyes (endothelial cell count).
Interestingly, one of my take-homes from this talk plus the previous one is that for those of you who have to remove and re-insert your lenses during the day, as in, the greens and purples in the first chart on this page, THAT IS NOT A BAD THING. I know it's a pain in the butt. But it's also ensuring your eyes get to breathe.
Finally, this presentation was quite helpful to me in getting a much better understanding of why there's such a debate about whether optometrists should be fitting sclerals on "normal" patients (as opposed to therapeutic use for those of us who can't see or can't get comfortable or can't keep our corneas safe any other way). The fact is, if safety outcomes are not well understood, the medical ethics of using the lenses on healthy eyes become very, very questionable. On the other hand... frankly, that mare already left the barn. It's being done.
Now I'm going to truncate even further:
Cornea & limbus diameter: Apparently, no one's ever bothered to study the size of this part of our anatomy since, er, something like 1961, it's just assumed and no one bothers to even cite a study about it. He gently suggested somebody ought to, and that this point matters for scleral lens diameter selection. And incidentally, all we really know about the limbus is that it's wider than it is tall.
Corneal edema. The "big picture" seems to be that on NORMAL eyes, we're not seeing excessive swelling so probably not huge things to sweat? But we need prospective studies. He also questioned how we're thinking about oxygen delivery to the cornea - suggesting that the question has been over-simplified and that it may not simply be a matter of increasing the available oxygen. Cited 3 studies indicating that there are other factors in play.
Increased IOP question (listed the studies and conflicting results). "The jury is still out." Talked about differences in biomechanical characteristics of cornea vs sclera - tonometer calibrated for cornea not sclera. Very interesting question: Aqueous can escape the eye via 4 routes; what happens when one of those is impeded (i.e. surface is covered with a scleral lens) - why wouldn't the other 3 routes pick up the slack? (in other words, let's not over-simplify the IOP question into a soundbite.)
Alright, I have plenty more to write up... but... more importantly, my daughter and I are going to go find a rare books store and get some dinner. So, all for now.
By the way - the next time slot, there were 3 simultaneous classes I wanted to be in so bad! I opted for Dr Johns' standing-room-only talk on pain, and Chaidie went to the lens care compliance session, so we had to miss out on the one about hydrogen peroxide systems. Can't win 'em all.