Laser Trabeculoplasty ALT, SLT, MLT for Glaucoma. Part 2 of 12 of “What’s New In Glaucoma Surgery” Presentation, a continuing education course for Optometrists presented by Patient-Focused Ophthalmologist, Dr. David Richardson on May 20, 2015.

Laser Trabeculoplasty For Glaucoma

Argon Laser Trabeculoplasty

Argon Laser Trabeculoplasty has been around for a few decades. Lasers have been available clinically for use in 1970s and Argon Trabeculoplasty really has kind of a neat history it’s one of those of many medical advances that were really kind of stumbled upon. When lasers first came out everybody thought they were really cool because they made holes. Alright? Made a hole on anything you want to make a hole at. And they made holes, when you bounced it off the mirror in the trabecular meshwork. Geez! Isn’t this obvious? Make a bunch of little holes in the trabecular meshwork. Get flow into the canal out the collector channel system- we’re good to go. So they tried that monkeys and sure enough they made holes but then what happens in the eye, as well as anywhere else when you make a you know hole or incision where it shouldn’t be, scarred-down, closed up. So the holes aren’t working but you know what if we laser these monkeys’ trabecular meshwork not quite enough to make a hole just enough to coagulate it- to melt in a bit, it actually results in the pressure going up! So now we’ve got a monkey model of glaucoma. How great is that – Well now we can induce glaucoma on monkeys and now we can study other treatments on these monkeys. So they took a failure and they created a laboratory success. Except that the monkeys – this is one of those stories (sorry it just keeps going)… except it turns out that some of these monkeys who had enough laser therapy to coagulate but  not enough to penetrate actually ended up with their pressures going down after the initial postoperative inflammatory response.

So some brights, scholars, scientists, researchers said, “Wait a second pressure went down, something’s going on this could actually be a treatment for glaucoma!” So, they titrate it down a little bit more. Not quite enough to, you now, make a big coagulative mess but enough to make some structural change, and lo and behold ALT – Argon Laser Trabeculoplasty was discovered. It was really stumbled upon. And to this day we really don’t know how it works. There are all these theories about how it stretches the trabecular meshwork in between the spots or it actually creates microscopic openings or tears. Nobody really knows. It works well for open-angle glaucoma. It can be performed in one to two sessions but the problem is it does still result in microscopic scars and also may limit future surgeries, alright. So surgeries that involved opening up that Schlemm’s canal, it can actually be problematic because now you’ve got these scars that are essentially sealing the canal, so surgery such as Canaloplasty and potentially some of the newer surgeries that are not yet available could be limited by Argon Laser Trabeculoplasty.

Selective Laser Trabeculoplasty

So more recently in the 1990s Doctor Latina developed Selective Laser Trabeculoplasty. Now, it’s called Selective Laser Trabeculoplasty because the laser is selectively absorbed by pigment. So, the melanin granules in the trabecular meshwork and the neat thing about it is that it only uses 1 percent of the energy of Argon Laser Trabeculoplasty, and does not cause coagulative damage. So because it doesn’t cause any coagulative damage, it doesn’t limit future surgeries. It doesn’t cause any kind of PAS we’ve all seen aggressive peripheral anterior synechiae. I call them saw-tooth PAS. When somebody has had aggressive ALT and it has, you look under gonio you can see little see saw-teeth. You won’t see that with selective Laser Trabeculoplasty. And because it doesn’t cause any Damage it can actually be repeated. So it works about seventy percent of the time. Works about as well as a drop, which is also about as well as Argon Laser Trabeculoplasty work so it’s not really any better in terms of how of effective it is but it’s its repeatable and it doesn’t close future doors. Selective Laser Trabeculoplasty when it first came out was crazy expensive. It was a one trick pony laser. So not too many people are going to be buying it. Not too many people did.

Micropulse Laser Trabeculoplasty

So, some companies developed another technology called Micropulse Laser Trabeculoplasty (MLT). This essentially segments the pulses into these tiny little super-fast pulses and by doing so you don’t get the Heat. You don’t get the increase in temperature. So you don’t get coagulative damage and there’s less damage in scarring but you get the same kind of result as you would with SLT or Argon Laser Trabeculoplasty at least according to the company documents. They just aren’t as many good studies on this this probably would have taken over and we will see a lot more of that except that now the SLT patent has just expired and so companies are now coming out with SLTs that are e significantly less expensive than seventy thousand dollars. So this this may go, by the way, side this is MLT.

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