Scleral Shape, Instrumentation and Lens Design
Hello there, and welcome to another Contacts with Conway.
In this edition, I’m in conversation with Dr Greg DeNaeyer, from Ohio in the United States.
Greg’s practice deals mainly with complex cases,
and I began the conversation by asking when he first got interested in fitting scleral lenses.
We join the conversation at that point.
If you would prefer to watch this video with English or Spanish subtitles,
please go to the cog in the bottom right hand corner of the screen,
and press to select your preferred option.
When did you start working with scleral lenses?
Greg: Well I work in an anterior ophthalmology practice, and currently we have 3 cornea specialists.
But I started back, with my first scleral lens fitting, in 2001, and what had happened was
I was using corneal GP lenses for patients who had keratoconus, or corneal transplants, some sort of irregularity.
And, I was also inexperienced at that time.
But what I was finding is that I was spending an inordinate amount of time
trying to get these relatively small corneal GP lenses to centre on the eye.
I might go through 4,5,6 lenses, and still may not even find success at that stage.
A colleague of mine at the Ohio State University College of Optometry actually recommended that I try,
what I had hardly even ever heard of before, was these scleral contact lenses.
And of course, back in 2001, there was just very few practitioners even around the world
that were utilising these devices.
So, I ordered a fitting set, a diagnostic set, from C and H Contacts out of Texas,
and that lens actually was the predecessor to the lens that you started with, which was the SoClear.
That lens, if I recall correctly was about 13.5mm in diameter.
But at the time, when I got the fitting set, it looked ginormous!
I still always remember the time when I first put a scleral lens on a patient’s eye,
without any education on the fitting process at all.
When I put the lens on the eye, it centred.
And at that stage, I remember thinking “Now this is where I want to go”
because these lenses have a lot of potential for the patient population that I was trying to serve.
Martin: Yeah, I remember again, with that product, I was sent on an exercise down in the Middle East,
trial by fire really.
To demonstrate the fitting, with very little experience behind me,
I was launched into a hospital in Jordan with probably 20 or 30 patients waiting for the first day.
They had a team of nurses to assist, but I got more experience in those two days of fitting that we did
in that hospital than I’d had in the preceding 18 months, I think.
So, mine was 10 or 12 years ago, but it’s absolutely exploded since then.
And we’re all aware now, and of course the big thing that you’ve been involved in is scleral shape.
What actually goes on beyond the normal range of the topographer.
Greg: Well, I’d been fitting scleral lenses for some years using diagnostic lenses, like everybody else,
and I realised at some stage that there had to be more to the fitting process than these diagnostic lenses.
In fact, when you really think about it, fitting with diagnostic lenses is certainly more art than science.
Martin: Yeah
Greg: The learning curve, especially for the novice practitioner can be very steep,
and much of that stems because up until recently, we haven’t been able to measure the anterior ocular surface
beyond the cornea.
So, we’ve had our traditional corneal topographers, which do a nice job of corneal measurement,
but we know from experience and from literature, that they’re virtually useless for scleral lens fitting.
So, myself, and a few other engineers, and another lab in the US, ended up forming a company
called Precision Ocular Metrology.
And our mission really was to create an instrument – a profilometer –
that we would now term as a corneal-scleral topographer.
This is an instrument that is able to not only measure the cornea,
but out onto the bulbar conjunctival scleral surface.
Martin: What year would this be? When did this start?
Greg: We started really about 2015.
Martin: Oh, so quite recently.
Greg: Yeah, and now we’ve obviously progressed quite quickly into the year 2020.
Martin: What was the technology that you had to draw on there?
Because it’s quite a different technology than is used in the traditional placido disk reflection
technology that’s used in a conventional topographer.
Greg: Right, so the placido disk of course is confined to the cornea and it can’t reflect off
or reach out to the bulbar conjunctiva scleral surface.
What we did with the sMap3D is we created hardware, an instrument that has two cameras and
one central projector, and what that arrangement allows is for the instrument to take
a series of triangulated measurements. And then it’s able to use something that’s actually not new,
it has been used for a while now, it’s called structured light.
Martin: When I first heard of this – it’s really very much like the sort of technology used in 3D printing.
Like scanning an image, isn’t it?
Greg: Well, in fact, what structured light is able to do for us is, the software can create
a 3-dimensional model of the ocular surface. And we can use that model to basically
measure sagittal height of the eye. Anywhere on the eye we want.
We can use that both, just for general measurement, but, as we’ll get into
during the course of this conversation, what’s important for us is scleral lens design.
Martin: So as far as the practitioner is concerned, he uses the instrument, it looks a bit space age,
compared with a conventional topographer, certainly more than an even more traditional keratometer.
He would actually instil fluorescein into the eye, which is different to what we have to do with a topographer.
And that’s because the light used is on the blue end of the spectrum.
So, you get some fluorescence and it’s done in almost complete darkness I take it?
You tune the lights down in the test room to as dark as you can, I take it?
Greg: Well its more helpful actually as you’re taking the test to have the lights dimmed,
but it actually doesn’t require you necessarily to have complete darkness.
But you’re correct in that the reason we have to have the fluorescein is because
of the way it measures the surface, it will not recognize the clear tissue of the cornea,
or the bulbar conjunctiva, the surface that you’re measuring out onto the sclera.
It would be invisible to the instrument. So, the fluorescein has to cover that surface
for it to be able to register data.
Martin: So, to make it more visible in other words.
Greg: Yes.
Martin: I see. So then, the instrument then produces a dimensional height map for whole area scanned.
You have to retract the lids, I take it, to get under and see that surface top and bottom?
Greg: That’s correct. In fact, actually, with the sMap3D, in particular,
what the practitioner will do when they do an examination is they’ll take 3 separate measurements.
So, there’s the first measurement which is the straight gaze.
And the clinician, and usually the patient will help out a bit, they’ll retract the eyelids as far as possible,
and they’ll take a straight gaze measurement.
Then we also take two more measurements, one where the patient looks down,
and then another one where the patient is looking up.
The reason that we do that with the sMap3D is because what we found is that on many eyes,
even if you’re retracting the lids as far back as possible, because of anatomical differences in patients,
including relatively small apertures or deep sockets, that you can oftentimes miss important data
underneath the superior lid, in the superior quadrant.
In fact, we published a study a few years ago in Eye and Contact Lens that showed that for the
straight gaze only measurement, 68% of eyes will have less than 50% of the coverage needed to fit
a 16mm scleral lens.
Martin: So, having had that data, then you upload that and turn it into a digital image of the eye.
How does that then help you with lens design? Will it translate directly?
Or is it then fed into a CNC lathe? How does that work?
Greg: There is software available to the practitioner to basically use the data and the image sets to
create their own customized version of a scleral contact lens.
The software actually gives the practitioner a starting point, it basically will fit the best design
scleral contact lens to the eye.
But then the practitioner can manipulate and in real-time the different parameters of the lens,
to customize it as he or she sees fit.
The other route actually which is more recent and new,
is that they have the ability to a completely free form customized lens that they call the Latitude scleral lens.
Martin: Is it linked specifically to one laboratory at the moment,
or can the practitioner use other lens designs as well?
Greg: Currently, as far as the automated type of process that you might use to design a scleral lens,
either the Europa or the Latitude lens, that is linked directly to Visionary Optics.
But a practitioner can own the sMap3D topographer and utilize the data to fit other types of lens designs.
So, they can use the instrument to measure for example the amount of scleral
toricity that might be apparent for a patient, or irregularity of the sclera, that type of thing.
And they can use that data when they’re fitting other types of designs.
Thank you for watching
Martin: Thank you for watching the first half of this conversation with Dr Greg DeNaeyer.
If you’ve enjoyed it so far, please join us for the second half of the conversation with some clinical experiences
with the new technology.
If you’ve enjoyed the video so far, please remember to give us a like,
share it with friends, and subscribe to our channel.
Thank you very much and I’ll see you next time.