Laser Complications
Chat Highlights
February 25, 2004

Norma Devine, Editor

On Wednesday, February 25, 2004, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Laser Complications."

P:  What types of lasers are used in glaucoma treatment and for what purposes?  

Dr. Rick Wilson:  The argon laser or the frequency doubled Nd:YAG are used for trabeculoplasty to lower IOP (intraocular pressure).  The argon laser is also used in gonioplasty to open a narrow angle.  The Nd:YAG laser is used to relieve pupillary block in angle-closure glaucoma.  

P:  Are the types of complications the same for all types of laser? 

Dr. Rick Wilson:  The argon laser burns, whereas the Nd:YAG cuts.  So the complications are different.

P:  Are complications from laser treatment common?

Dr. Rick Wilson:  No, they are not common.  The biggest problem is that they are not always successful.  That has a lot to do with the doctor's careful selection of patients, rather than with the doctor's ability to perform the procedure.

Moderator:  Can you elaborate on that statement?    

Dr. Rick Wilson:  Laser trabeculoplasty is effective for primary open-angle glaucoma, normal-tension glaucoma, pigmentary glaucoma, and pseudoexfoliative glaucoma.  The older the patient, the better.  I rarely perform trabeculoplasty on patients under 60 years of age, unless they have pigmentary glaucoma.  The patient needs to have an open angle and good pigmentation of the trabecular meshwork.  Without an open angle and good pigmentation, there is little hope of success with a trabeculoplasty, although many doctors go right ahead anyway.

P:  What special training must doctors have before using laser to treat glaucoma?  Are ophthalmologists qualified to perform laser surgery?   

Dr. Rick Wilson:  They perform laser treatments with a teaching ophthalmologist looking on through the teaching scope and advising.  Ophthalmologists, the Eye MDs, are trained to use lasers. 

P:  Is there a chance of a long-term loss of visual acuity after SLT?  

Dr. Rick Wilson:  I have not heard of it.  It is possible to have a large rise in IOP after the treatment.

P:  During the SLT procedure, the zapping noise started to get on my nerves.  Is it true that SLT is so new that all the complications are still unknown?  

Dr. Rick Wilson:  I don't consider it that new.  Mark Latina has been working with it for at least eight years, I bet.  It seems less invasive than the argon that we have been using since the late '70s

P:  Is there any more information about how many times the SLT can be repeated?

Dr. Rick Wilson:  Not yet.  It hasn't been around long enough. 

P:  Is it possible for the laser to hit a nerve? 

Dr. Rick Wilson:  Yes, but the bigger problem would be hitting the center of the retina.

P:  Are the terms argon and Nd:YAG related to ALT and SLT, respectively?

Dr. Rick Wilson:  Argon is the "A" in ALT (argon laser trabeculoplasty).  SLT (Selective Laser Trabeculoplasty) uses a frequency-doubled Nd:YAG.

P:  Are CO2 lasers ever used?

Dr. Rick Wilson:  CO2 lasers are used investigationally in creating partial thickness filtration procedures.  CO2 lasers cut, but the wavelength is absorbed by water, so the fluid in the eye stops the laser.  

P:  The first doctor I consulted wanted to use a cyclodiode laser.  But after I read the Chat Highlights, that did not seem right for me, because I have uveitic glaucoma.  What does the diode laser do and why is it not recommended for uveitic glaucoma? 

Dr. Rick Wilson:  The cyclophotocoagulation of the ciliary body with the diode laser kills the part of the part of the eye that makes the clear fluid in the eye.  Since the inflammation in uveitis can cause the ciliary body to make less fluid with time, you would be better served by increasing the outflow of fluid from the eye than by cutting down the inflow.   You made a good decision.  A knowledgeable patient is empowered.

P:  A friend of mine had two separate laser treatments.  The first was painless and he lost no vision.  The second one was painful and he noticed a loss of vision.  Is there an explanation?

Dr. Rick Wilson:  Were they the same type of laser?  Perhaps they were different lasers, with the second being the diode cyclophotocoagulation.

P:  I had a great deal of pain with one laser I had.  The pain was so bad the procedure had to be stopped and ice was applied to my eye.  The laser did not do what it was supposed to do.  What caused the pain?

Dr. Rick Wilson:  Too much energy can cause inflammation or a pressure rise.  Both hurt.

P:  Are there large variations in the choice of power used during ALT?  

Dr. Rick Wilson:  I think it is prudent to use ALT only in patients who have a good amount of pigment in the trabecular meshwork.  With pigment to absorb the light energy of the laser, the doctor only has to use 200 to 500 mW of power. Without pigment, doctors may use up to 1000 mW.

P:  How often are there misses with laser treatment, and would you say this is the fault of the doctors or something related to individual anatomy and totally unpredictable?

Dr. Rick Wilson:  There are often small misses that don't seem to do any harm.  If the shots are way off (and I think such shots are quite rare),  they can cause burns to the cornea, iris, or retina.

P:  Is it possible to lower the IOP before the laser treatment to prevent damage to the optic nerve from a spike in the IOP?

Dr. Rick Wilson:  Yes, Iopidine and Alphagan are quite good at preventing IOP spikes.

P:  Which has the greater advantage:  laser or medication?  

Dr. Rick Wilson:  Most patients use the medications first, and lasers if that doesn't work.  The laser would be a better choice for those who (providing, of course, they meet my criteria for a good prognosis with laser, as described above) have trouble remembering to take their drops or paying for them.

P:  What constitutes success in laser treatment?  That is, what does the surgery really accomplish, and how long does the effect last? 

Dr. Rick Wilson:  A peripheral iridectomy opens the angle recess in narrow angles and, for almost all patients who don't have damage to the trabecular meshwork, cures them of the problem.  A good result for ALT and SLT is a 30 to 35% drop in IOP that lasts for three to five years.  

P:  Would you consider doing SLT on a patient with a severely damaged optic nerve?

Dr. Rick Wilson:  Yes, if there was good pigment, the age is greater than 60 years, and if a 20% drop in IOP would be adequate to safeguard the nerve.  If it wouldn't be, then moving directly to a trabeculectomy would be preferable.

P:  Have you seen many 30 to 50% decreases in IOP after laser surgery in normal-tension glaucoma (NTG) patients?

Dr. Rick Wilson:  Yes, I've seen 30% decreases in IOP in NTG, and 35% some of the time.  Over that, rarely.  In an 85 to 90+ year-old patient with pseudoexfoliative glaucoma, a 50% drop is possible.  Most of the time a 30% drop with the ALT is doing well.

P:  Can lasers be repeated in the same eye after a short interval?

Dr. Rick Wilson:  That depends upon what you're trying to accomplish.  You would not want to repeat an ALT once the 360 degrees of angle had been treated.  Working to open a peripheral iridectomy might take several lasers over a matter of days.

P:  Would a doctor use laser to "buy time" before going to incisional surgery? 

Dr. Rick Wilson:  It would be rare for me to try to buy time with a laser.  If the pressure is that dangerous, it might be better to just move ahead.

P:  Are there any alternatives to the traditional trab or shunt for young patients?

Dr. Rick Wilson:  There are alternatives for those under three years of age; otherwise, no. 

P:  Please explain how stem cell research could be used for loss of vision from glaucoma.  

Dr. Rick Wilson:  High pressure kills cells in the retina and the nerve cell body (fiber) that takes the light impulses back to the brain.  If the IOP is brought to a safe level, and cells that have the potential to grow into replacement cells are injected onto the retina, they can be induced to develop as desired and replace the dead cells.

P:  So if these new stem cells grow, then the lost vision will be restored?  I'm 27 years old.

Dr. Rick Wilson:  That is the promise with some animal research, which is surprisingly better than expected.  Luckily, the center part of the vision is left till the end in glaucoma and provides good acuity without much visual field. That is a situation for which stem cells offer great hope in repopulating the retina with healthy cells, once the IOP has been nicely controlled.  If you are only 27 years old, that will happen in time to help you, especially if we have a change of government next year.

Moderator:  We have a guest who lives in Montana and cannot find a glaucoma specialist.  Can you help?  

Dr. Rick Wilson:  David Boes, M.D., Great Falls Clinic, Great Falls, MT (Phone:  406-454-2171).  Dave served a Fellowship at Wills.    

Moderator:  We also have with us a patient in Brussels, Belgium, who stayed up very late to give us good news about her trabeculectomy three weeks ago. 

P:  Yes, and to say thanks for educating us, Dr. Rick.  This is a great web site.

Dr. Rick Wilson:  You're welcome. Have a great week, everyone.   Elliot Werner will be with you next Wednesday, as I will be at a meeting.

End of highlights for February 25, 2004.

On March 3, Dr. Werner discussed "Finding the Right Treatment" in the Chat room. Click here for highlights of that meeting.

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