Laser Trabeculoplasty
Chat Highlights
September 16, 2009

On Wednesday, September 16, 2009, Dr. Michael Pro, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Laser Trabeculoplasty".

Moderator: Tonight's topic is laser trabeculoplasty (LT). Dr. Spaeth, what is laser trabeculoplasty?

Dr. George Spaeth: Well, the laser part is easy; trabeculoplasty is a misnomer held over from the early days. It was thought that applying heat changed the structure of the trabecular meshwork—the drain of the eye—and let the fluid run out more easily. However, it became apparent that the mechanism was actually different.

The way the treatment works is still not clear, but it is likely that the heat, or the trauma from the other types of laser used, causes the cells to secrete an enzyme that makes the junctions between the cells looser and therefore leaky, so the fluid leaks through the cells and the pressure is lowered.

One of the really good things about LT is that it improves outflow and does not decrease inflow.

P: What types of different lasers are there to decrease IOP?

Dr. George Spaeth: All of the lasers have basically the same effect. That is, they traumatize the cells. They can do that with heat (argon) and explosion (so called "selective” laser trabeculoplasty), and so on. The alleged advantage of the newer types is that the trauma is less likely to cause scarring.

P: What is considered a successful trabeculoplasty?

Dr. George Spaeth: The only benefit of the LT is lowering of stabilizing the pressure. If the pressure is lowered about 30 percent then that is a great result.

P: How much does the skill of the physician play in the success of the procedure?

Dr. George Spaeth: A lot: the applications have to be to put in the right place in a tiny area.
If the power is too high the LT causes scars and can make the pressure rise; if the applications are put on the ciliary body (right next to the trabecular meshwork) the eye becomes inflamed; if the applications are put on the cornea the pressure is not lowered. The power has to be adjusted for the person being treated.

P: Are any of the lasers more effective in patients under 50 years of age?

Dr. George Spaeth: It is really important to choose the candidate carefully. Laser Trabeculoplasty only works with primary open angle glaucoma in people over 40 years old, or in cases of pigmentary glaucoma, or exfoliation syndrome glaucoma. It usually makes other types of glaucoma worse.

P: If one SLT did not decrease pressure will two, three or four treatments decrease pressure? Is there anything to lose by repetitively doing the procedure?

Dr. George Spaeth: Bruce Shields just published a paper showing that a second SLT can help, even when the first did not, however, it has to be a suitable case.

Moderator: What makes a suitable case?

Dr. George Spaeth: When the SLT works in one eye it usually is likely to work in the other. A suitable case would be: A patient with primary open angle, pigmentary (POAG), or exfoliation syndrome glaucoma, age 40 or older with clear corneas, no inflammation and wide open angles.

P: What eye drops are usually used prior to the trabeculoplasty? Are they the same no matter which of the procedures discussed this evening will be performed?

Dr. George Spaeth: Prior to LT it is customary to use Iopidine or Alphagan or a drop like that to prevent a pressure spike. Some people can't take any of those so Trusopt or Azopt or even Pilocarpine can be used.

P: What is the vision like in an eye that just had a trabeculoplasty? Is vision affected by the procedure in the short-term or long-term?

Dr. George Spaeth: The vision will be momentarily (one hour) blurred from the goop that holds the mirror used to direct the laser into the angle. That is slight and temporary. Sometimes there is a slight blur for a day due to inflammation, but usually there is NO effect on the vision.

The treatment is done by anesthetizing the eye with a drop and then putting a mirror on the eye in the form of a small lens. Then the power is applied; it takes about 10 minutes total to give the 50 or 100 spots of power. I almost always give 100 applications. Some doctors like to use fewer, but the treatment is less likely to work.

I really like laser trab because -in the right person- the treatment is SAFER than drops and works a bit better, though not forever.

P: Does a trabeculoplasty in one eye effect the contralateral eye? Will the pressure decrease in the contralateral eye if the procedure was a success?

Dr. George Spaeth: There is some evidence that the LT in one eye causes a slight lowering of pressure in the other eye, but this is not certain. If it does cause lowering of pressure in the other eye, it is usually not enough to help.

P: Should pregnant or breastfeeding women avoid laser trabeculoplasty? Are their results different due to the pregnancy?

Dr. George Spaeth: There is no reason for any appropriate person to avoid LT. It does not have systemic effects. Isn't that great? One of the reasons I so like LT is that it HAS NO systemic effects, unlike EVERY drop.

P: Is laser trabeculoplasty a must for all persons who have POAG, even those who are over 85 years of age?

Dr. George Spaeth: If I had POAG, I would want SLT or ALT as the first treatment; if it did not work. I would then use drops. Is it a necessity? No. Can it help? Yes, though only about two thirds of people get a pressure lowering.

P: What is an MLT (micropulse laser trabeculoplasty)? Is that something new? Is it better?

Dr. George Spaeth: I think the old-fashioned ALT is probably as good as any; the newer techniques may be advantageous, but I'm not sure. There may be no real definite advantage except that maybe SLT is safer to repeat than ALT.

P: Is a laser trabeculoplasty ever performed on children?

Dr. George Spaeth: No, never on children.

P: How many holes are made in an SLT procedure?

Dr. George Spaeth: You don't make ANY holes; the cells are just tickled. If you made a hole you would be using vastly too much power and would make the eye worse. The person having the treatment should basically not feel anything happening

P: Dr, what is the difference between A (Agron) LT and S (selective) LT?

Dr. George Spaeth: Argon is a blue light laser that makes heat. ALT is an explosive type of laser that send a shot that lasts only a millionth of a second.

Argon laser exposures are much longer, usually one tenth of a second. The laser has to be on the trabecular meshwork long enough to build up heat.

The SLT does not cause heat. That is its alleged advantage—no scar is produced, but that's too simple an explanation.

P: Is there a difference between a laser and a lasik procedure?

Dr. George Spaeth: LASIK is a procedure in which a type of laser is used to reshape the cornea; Laser Trabeculoplasty (LT) treats the inside of the eye and does not reshape anything.
So yes—there is a huge difference: different type of laser, different purpose, different surgeons, and different machines.

P: Does the effect of LT (either type) last a certain time? If vision loss still progresses would you try again?

Dr. George Spaeth: On average the pressure lowering lasts five years. I have some patients in whom it lasted 25 years, and some three months. If it lasts five years and the person still needs pressure lowering, repeating it can help. People need to know that the treatment may not work.

P: What happens to the one third of patients in whom LT does not lower pressure? Do you repeat it or try something else?

Dr. George Spaeth: If the laser does not work it usually is not worth trying again, although with SLT if the treatment was slight, doing it again with more power can sometimes help.

P: Doctor, with POAG and stable IOP (intra-ocular pressure), should I continue with my two drops, or should I consider SLT? ALT made no change in my IOP. I am in my late 50s.

Dr. George Spaeth: “If it ain't broken don't fix it.” If you are doing well on your medications with controlled pressure, no change in disc or field, and no symptoms form the drops, you can do no better. But if you are not doing well, or having symptoms from side effects of the drops, a laser trabeculoplasty may be good, if you have the right eye for it.

P: Dr I am confused about ALT. Is it less then a second or more then a second of laser blast?

Dr. George Spaeth: ALT is a one tenth of a second; SLT is a one millionth of a second application.

Blast is probably not the right word. Lasers can blast missiles out of the sky, but they also can be so gentle that they can't even be detected except by really sensitive instruments

P: Doctor, I had an ALT in my right eye, then a pressure spike, and then different drops. My pressure was lower (18 on my last visit), but my vision loss is progressing in both eyes. I think the ALT was about 4 or 5 years ago. Is it time for a glaucoma specialist?

Dr. George Spaeth: If your vision is getting worse something is wrong, either macular degeneration, or cataract, or progressive glaucoma, or something else. Make sure your doctor answers your question, which is “Why is my vision getting worse?”

Communication is KEY—both ways, give and take.

P: Are there any new lasers out there?

Dr. George Spaeth: There are new lasers. I don't really think they make much difference. The challenge is to use what we have well now.

Moderator: We're out of time for the evening. Thank you so much for joining us, Dr. Spaeth. It's always a pleasure to have you here.

Dr. George Spaeth: Thank you for the great questions! The pleasure is mine as well.

On October 7, Dr. Pro discussed "Visual Field Findings" in the Chat room. Click here for highlights of that meeting.

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