Lasers for Glaucoma
Chat Highlights
February 13, 2002

Norma Devine, Editor

On Wednesday, February 13, 2002, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Lasers for Glaucoma."

Moderator:  Dr. Rick Wilson is our guest tonight.  The topic is "Lasers for Glaucoma."  Welcome, Dr. Rick.  

Dr. Rick Wilson:  Hello, everyone.  I'm ready for the first question.  Shoot! 

P:  Is laser for older folks only?

Dr. Rick Wilson:  Laser can be used to make a hole in an iris that is too close to the drain in the eye, regardless of age.  Laser used to lower IOP works better the older the patient is.  There also must be enough pigment in the drain to absorb the laser energy which, after all, is just light.  

P:  How long do the effects of laser surgery last?  

Dr. Rick Wilson:  A laser iridectomy (hole in the iris) usually lasts forever.  A trabeculoplasty may not work at all, but in patients with a good prognosis the success rate is 45 percent at five years. 

P:  Is there a difference between an iridotomy and an iridectomy?

Dr. Rick Wilson:  Literally different,  but in real life the same thing.

P:  Could you explain the role of pigment in predicting how well either SLT (selective laser trabeculoplasty) or ALT (argon laser trabeculoplasty) is likely to work?  Thanks.

Dr. Rick Wilson:  SLT targets the pigment in the drain,  rather than making a small, indiscriminate burn in the drain.  Both SLT and ALT require color to absorb the light energy of the laser.  Otherwise, much of the light is reflected back off the drain.

P:  I asked my glaucoma specialist if the filtration surgery I needed could be done by laser and she indicated cutting surgery would be best.  Why is that?  

Dr. Rick Wilson:  We have not found a happy medium creating holes in the eye with lasers.  Small holes have fewer complications, but heal shut.  Large holes don't heal up as much, but the resulting low pressure after surgery results in a high incidence of complications.  Until we come up with a way to keep the small holes from closing, cutting surgery seems to be much more predictable and controllable.

P:  I had trabeculoplasty in the left eye and it did absolutely nothing.  Now the doctor wants to use the laser in the right eye, too.  Could that have a different result? 

Dr. Rick Wilson:  The tendency for one eye to act like the other is definitely there.  However, if your doctor has enough experience, he or she will adapt the second operation to allow more outflow and use more mitomycin to cut down on your tendency for the scar tissue to close the drain.  

P:  If a trabeculectomy fails due to healing, would the problem also affect the success rate with the laser?

Dr. Rick Wilson:  No.  We usually try the laser first, especially in African-Americans.

P:  Do you believe that cyclophotocoagulation (using laser on the part of the eye that produces aqueous humor) is over- or under-utilized?  Should it always be considered ONLY as a last resort?  How do its success rates compare with those of other surgeries for glaucoma today?

Dr. Rick Wilson:  It is always more physiologic (natural) to increase the flow of aqueous fluid out of the eye toward normal rather than cut down the amount of fluid the eye makes.  The lens and cornea of the eye have no blood supply.  They depend entirely upon the fluid the eye makes carrying oxygen and nutrients to them.  For the first six weeks after surgery, a cyclophotocoagulation in the animal model cuts down the amount of oxygen in the front of the eye by sixty percent, if I remember the Japanese study accurately.

P:  A few months before my intraocular pressure jumped from 18 to 38 mm Hg under medication, I had an ALT in both eyes.  Could that have had any influence on such a jump in IOP?

Dr. Rick Wilson:  It could, especially if you were young or a lot of laser energy was used, or   because you had little pigment in the drain.  If so, the doctor had to increase the amount of energy used to get a visible result from each burn of the laser.

P:  What kind of complications occur from lowering pressure with SLT?

Dr. Rick Wilson:  I have seen few, if any, complications, from SLT.  It is certainly possible to get a pressure rise after the laser and transient inflammation.  Usually both are gone by a week.

P:  I've had iridotomies in both eyes, and when I look into a bright light wearing glasses, I can see a pin-hole type light reflecting in the glasses.  I suspect this is the iridotomy. The light seems to be coming from the top in both eyes, and it comes and go.  If I can see this type of light, does that mean that the iridotomies are still open? 

Dr. Rick Wilson:  I would think so, especially if you squint your eyes and the light, which should be coming from the bottom, goes away.

P:  Does laser cause scarring?  

Dr. Rick Wilson:  Certainly, but the scars are usually small.

P:  Does the long-term use of many glaucoma medications influence the success of laser surgery?  

Dr. Rick Wilson:  The long-term use of topical medications causes low-grade inflammation in the conjunctiva, which causes more scarring when surgery is performed in the eye or the eye is injured. 

P:  Is there any other type of laser surgery for glaucoma other than ALT and SLT?

Dr. Rick Wilson:  There is gonioplasty, which remodels the iris near the drain (trabecular meshwork) to pull the iris away for the drain.  The laser can also be used to open up a small pupil.  There's also photocoagulation of the ciliary body (the part of the eye that makes the aqueous fluid) to cut down on the amount of fluid the eye makes.

P:  Is laser surgery effective in helping raise low IOP?

Dr. Rick Wilson:  That's a tough situation.  Steroids with or without atropine may help.  Sometimes an injection of Healon,  a vitreous substitute, will help for a while.

P:  I have developed a secondary cataract in my right eye, and may have to have laser.  What type is used for that procedure?  

Dr. Rick Wilson:  A Nd:YAG laser is used to make a small opening in the back capsule behind the intraocular lens.  It doesn't hurt and you can't even see the laser as it does its work.  You do, however, see the aiming laser. 

P:  Would you choose SLT or incision in a 68-year-old male?

Dr. Rick Wilson:  I can't say without a lot more information.  Have you tried all the medications?  Do you have good pigment in the drain?  What kind of glaucoma do you have?  All these things need to be considered in  making a learned opinion.

P:  Is laser surgery effective in raising low intraocular pressure? 

Dr. Rick Wilson:  If the IOP is low because of a cyclodialysis cleft (a cleft between the layers of the eye), it may be able to be closed by a laser.  A laser can be used to cause inflammation to a bleb if it is working too well to heal it down somewhat, resulting in higher IOP.

P:  How does gonioplasty differ from peripheral iridectomy?

Dr. Rick Wilson:  An iridectomy equalizes the pressure behind the iris (usually higher because the fluid is made in back of the iris) and in front of it. This lets the iris fall back from the drain, allowing space for the iris to "accordion" as it dilates, without the iris getting caught in the drain. A gonioplasty just shrinks the iris back in front of the drain with heat -- like shrink wrap.

P:  Once, while having a suture removed with the argon laser, I saw a bright green light flash across the bottom of my eye and it hurt.  Was that normal?  

Dr. Rick Wilson:  Postoperative eyes are often light-sensitive, so if you got a bright flash in our eye it would hurt.

P:  Why is laser used instead of a blood injection?

Dr. Rick Wilson:  I don't use it much.  I have had better luck with blood injection.

P:  How long after surgery are eyes sensitive to light? Mine have been sensitive to light for four years.  

Dr. Rick Wilson:  Usually three to six weeks. 

P:  Statistically speaking, what percent of incision filtration surgical procedures result in total elimination of medications and no repeat surgery?

Dr. Rick Wilson:  That depends upon how long the period is, as the success rate decays forever.  More than eighty percent may start out without medications, but the rate drops with time.

P:  How serious are iris cysts?  An eye doctor thought I might have them.

Dr. Rick Wilson:  Iris cysts can be serious, but are easily discovered with the ultrasound biomicroscope.

Dr. Rick Wilson:  Good luck all.  Dr.  Jeff Henderer will take over for me next week,  as I will be at a meeting in San Francisco. 

Moderator:  Thank you, Dr. Rick.  Have a good trip.  Good night.

End of highlights for February 13, 2002.

On February 20, Dr. Spaeth discussed "Glaucoma Medications" in the Chat room. Click here for highlights of that meeting.

Click here for the most recent glaucoma chat highlights and links to the chat archives.

Click here for upcoming glaucoma chat events.