 that kind of leading up to a discussion of the case. And I wanted to preface that by saying it's complicated, though. And what I did was just kind of took some of the highlights that I thought was interesting. So this is by no means meant to be an exhaustive coverage of the history of eczema or laser or anything like that. And there's definitely things that are left out of here. Okay, so just kind of to start out with, what is an eczema laser? Well, it's a laser that where the light that's generated falls in the ultraviolet spectrum. So that's sort of the major class that it falls into. Eczema stands for excited dimer. And under appropriate conditions, it was discovered in the 70s. If you have high pressure and electrical simulation, you can force molecules to come together that don't really like atoms to come together that don't like to come together. And that consists of the eczema. And then as that sort of pseudomolecule relaxes, it can be made to emit laser light in the UV spectrum. And so you can see this is projecting pretty small. It may be hard to see. So there are a few lasers that are actually really eczemas because this is more of a dimer. Most eczema lasers are actually properly called exaplex lasers because it's an excited complex. And so if you can read these numbers here, all the residents and fellows know that this is the wavelength that we're interested in, 193 nanometers. And that happens to be an argon fluoride combination. So the laser was first developed in 1970 in Moscow using a xenon dimer by Dr. Basoff here, who had I think about six years earlier had won the Nobel Prize for his work in the development of lasers. So he had already done some very important work in terms of developing lasers. So eczema laser was initially studied on the eye in the military by this gentleman here, John Toboda, I guess, who had the interesting title of investigator of ocular damage. Sounds like an interesting job for the military. So as part of this job, he was sort of messing around with zapping people's eyes with the lasers. And when he did that with this argon fluoride laser, he noted that at certain energy levels, the laser would imprint an indent of the laser beam on the corneal epithelium. But he noticed that this defect healed very quickly. And so that made them think that maybe this laser was able to deliver energy to a specific location but not create a lot of collateral damage because it's able to heal so quickly. Dr. Trockel is one of the people who made very important contributions to the development of eczema laser. He was an ophthalmologist at Columbia University. And early in the 80s, he was impressed with how well the YAG laser could cut through the posterior capsule. And so he began thinking about using lasers to reshape the corneal for refractive means, for the correction of refractive air. And in the early 80s, Trockel was introduced to Dr. Srinivasan. That's my best attempt. Trockel. I appreciate all the corrections here. And so this fellow here was working at IBM. And he was using this laser to etch microprocessors. And he'd actually done a little bit of work to show that the laser could precisely remove organic tissue, again, without producing collateral damage. So this is a very nice picture of what the laser could do, etching little blocks out of a human hair. So he called the process ablative photo decomposition. And it had three main stages. So first was absorption of the laser energy. Now, a single photon of light with this particular wavelength has an energy of about 6.4 electron volts. And this exceeds the energy required to break molecular bonds in the cornea, which is estimated at about 3.6 electron volts. So if you have enough density of laser energy, you can break the tissue into small molecular fragments, which have some energy left over. So we're putting in over 6 electron volts. We're using less than 4. So they actually have a little bit of kinetic energy left over. And the result of that can be a very impressive little actual like a mushroom cloud of stuff that is zapped and broken into molecular little fragments and then ejected with kinetic energy. So this is actually a photograph of cornea that was zapped with one of these eczema lasers. And this is the resulting laser plume of tissue that was actually ablated. So early in the 80s, there was characterization performed in multiple animal models. In 1983, there was a publication of this initial seminal paper that first reported the use on enucleated calf corneas. Dr. Krueger joined Trukel in the early 80s and worked out optimal laser conditions for ablation over a couple of years. So they tried lots of different wavelengths. They tried different energy levels. They tried different sizes of the laser pulses and things. And then they sent some of their tissue to Dr. Marshall in London who performed a histologic evaluation of them. And so this was just one of the images showing that the 193 nanometer wavelength really worked a lot better than some of the other wavelengths that they tried. So for instance, at 248 nanometers, you can see there's really some pretty ragged edges here of the tissue, whereas at 193 nanometers, you get nice smooth edges in the corneum tissue. So one big concern in the field was that if you're going to zap the corneum with the laser, aren't you going to form a scar? So Marshall's work on the histology of the tissue was really important to establishing what happened and was critical in leading to the acceptance of the technology. So he showed that the treatment left a smooth surface without a scar. And at the ultra-structural level, he discovered the formation of the pseudomembrane, the border of the treated tissue. And it was felt that the pseudomembrane provided a template on which the epithelium could grow. It was very, very thin. It was on the range of 140 nanometers. This is a picture from one of his papers. Here you can see sort of the layers of the corneal stroma. You can see the alternating layers. And then here are the... There's an alternating, very dense band and then a lighter band. And this is the pseudomembrane. Each one of these bands is about 70 nanometers. So the first clinical refractive application in human subjects was performed by Dr. Sealer in Germany in 1985. And he used... How do you actually pronounce that? Sealer. Okay. Thank you. He used the laser to create arcuate transverse excisions. You know, it's never... You know, the papers don't come with pronunciation guides. And there's no way for me to know. So I do appreciate it. Next time, I'll run my talk by Dr. Manless, who will be able to tell me how to pronounce all these. Yeah. So he basically used it to make transverse excisions across the steep axis to correct the stigmatism. And they presented the first laser prototype at AAO in 1985. And the idea was to use the laser as a replacement for the diamond knife in RK. Unfortunately, it really didn't work very well for this, actually. The diamond knife worked better. So just a year later, they presented a prototype for the use of broad-beam laser in 1986. And that subsequently led to the development of the first physics prototype in 1987. So the first broad-beam PRK was performed in 1988 by Dr. McDonald at LSU. And it was performed on an eye that was already going to be enucleated from malignant melanoma. And importantly, they found that after the cornea healed, it remained transparent. When they looked at the specimen pathologically, it looked like there was a nice uniform removal of Bowman's layer and the superficial stroma and the overlying epithelium looked intact. Now later on that same year, she performed the first clinically successful PRK on a patient with what was termed in the paper a non-sided myopic eye with optic neuropathy. Now later they actually found that this patient had functional vision loss and recovered with 2020 uncorrected distance acuity. So this was kind of a fortuitous, you know, finding this. I thought it was very interesting. Questions or attempt to? Yeah. Well, I looked at all of those papers that describe flap complications and it wasn't described in any of those, but there may be some other papers that just describe strange, you know? No, I mean, I think that, and that's the point that Dr. Ambadi was making, was that it requires quite a bit of force to dislocate the flap. And so there are, we definitely consider what they do for a living and what their hobbies are and that's a factor. And we discuss this risk with them and let them make that decision. In some cases, we will sort of more strongly recommend towards PRK. For instance, we saw a patient with Dr. Newfer who worked as a police officer and they're at big risk, right? For people to try to, going at their eyes or getting a hit or something like that. And so, you know, they decided that they thought PRK would be better in that case. There are other factors that are involved as well like the corneal thickness and what the correction is exactly and stuff that will sway in one direction or another. But, you know, if they're really into contact sports, martial arts or something like that when they're going to get hit in the face or their job maybe puts them at risk, that's just one of many considerations.