When is laser surgery appropriate in the treatment of glaucoma?
There are a number of different laser treatments applicable to glaucoma, which can be a major source of confusion to patients. Angle-closure glaucoma is an anatomic disease. The drain of the eye (the trabecular meshwork) is usually normal, but the iris is forced against it, usually by fluid pressure behind the iris, similar to putting a stopper over the drain of a sink. Laser iridotomy is the definitive treatment for angle-closure glaucoma. Medications should be used only, as a temporary measure or if the IOP is still elevated after laser iridotomy has been performed. A second laser procedure, peripheral iridoplasty, is indicated in a small percentage of patients who have a more complicated for of angle-closure glaucoma known as plateau iris, when laser iridotomy is insufficient to eliminate the blockage of the trabecular meshwork by the iris.
In open-angle glaucoma, the trabecular meshwork is functionally impaired. Argon laser trabeculoplasty is the treatment applicable to the various diseases, which fall under the category of open-angle glaucoma. The most common of these are chronic (primary) open-angle glaucoma, exfoliation syndrome, and pigmentary glaucoma.
It is still controversial as to what point to intervene with laser trabeculoplasty in open-angle glaucoma. When the procedure was first developed, it was regarded as a step between maximally tolerated mediations and surgical intervention. However, over the past 15 years, it has become realized that , whereas some patients tolerate medications extremely well with no side effects, whatsoever, others are seriously hampered in their quality of life. At the same time, surgical techniques have advanced and complications have diminished. The Glaucoma laser Trial, a national multi-institutional prospective study sponsored by The National Eye Institute, showed that initial laser trabeculoplasty, performed in newly discovered chronic open-angle glaucoma patients prior to the institution of any medical therapy, compared favorably at two years of follow-up to initial treatment with medications. However, at the present time, most glaucoma specialists do not perform laser trabeculoplasty as the primary mode of therapy, but rather only if medical therapy is insufficient to control the disease. Patients who are glaucoma suspects (ocular hypertension) who have no detectable optic never or visual field damage are not candidates for laser trabeculoplasty at the present time.
What would the IOP be in a typical patient when laser surgery would be an appropriate decision and what are the risks involved?
There is no specific IOP at which laser trabeculoplasty is indicated. The pressure which is too high for an eye is that pressure at which glaucomatous damage progresses. If the pressure is in the 40s, ALT is unlikely to control it. I personally do not believe that ALT is very useful in normal-tension glaucoma. ALT is by and large a safe procedure. Rarely, patients can get a prolonged evaluation of IOP or severe inflammation.
Does scar tissue develop after laser surgery, causing future problems?
Scar tissue can form if the laser spots are not placed in the appropriate site on the trabecular meshwork but are placed too far posteriorly toward the scleral spur and iris insertion.
Is it true that the benefits of laser surgery to reduce pressure are temporary and, if so, can the surgery be repeated and how often?
Laser iridotomy for angle-closure glaucoma may close in the early period after the laser is performed, but can easily be opened up. In a few patients, late closure occurs, and is also easily opened. In ALT for open-angle glaucoma, about 90% of patients get an initial response and 80% have a response at the end of one year. The procedure wears off at a rate of approximately 10% per year, so that somewhat less than half of patients treated are still under control at the end of five years. However, this certainly is a long enough period of time to make it worthwhile undergoing the procedure.
The trabecular meshwork runs circumferentially around the eye for 360 degrees. Many ophthalmologists treat 180 degrees, using 50 spots, and if the pressure comes under control, stop at that point. Then, if and when the initial treatment wears off, the second 180 degrees can be similarly treated. Some ophthalmologists believe in treating the entire 360 degrees initially. Repeat ALT, in which an additional treatment superimposed upon the first area of treatment is applied, has been advocated. I very rarely do this. Many patients can get a rise in IOP instead of a lowering. If the initial treatment of 360 degrees (whether performed in one session or two sessions) is insufficient or the effect wears off, I feel that the next step should be surgical intervention.
Would you recommend a second opinion before agreeing to laser surgery?
There is no blanket indication for a second opinion. Some insurance companies require one, some patients feel better having one, and some ophthalmologists feel better getting one. I am personally in favor of second opinions if the patient would like to have one.
Is there a time when laser or traditional surgery for glaucoma will replace taking eye drops and medication to control eye pressure? For a person who only has to take one eye drop and who responds well, surgery may not be an option, or at least a necessary optional. However for a person who needs three or more eye drops or who has multiple side-effects (headaches, dim vision, upset stomach_ surgery seems to be a better option.
Over the past decade, doctors have become more interested in laser and surgical approaches to early glaucomatous damage. The National Eye Institute/National Institutes of Health have been involved in nationwide research projects to assess the role of early laser or filtering surgery in the management of glaucoma. The Glaucoma Foundation can provide information regarding these study locations for you. The Glaucoma Laser Trial documented the safety and efficacy of laser surgery as a treatment for open angle glaucoma and has contributed to tits widespread use . The Collaborative Initial Glaucoma Treatment Study randomizes patients to surgery or medication as the initial therapy for open angle glaucoma. This project is still enrolling patients. Since glaucoma surgery is relatively safe and effective, it can be used for those people who have to take multiple medications or are intolerant of them. Glaucoma therapy needs to be individualized for each patient and alterations in medical therapy should be discussed with your doctor. J.M.L.
Does the amount of pigmentation in the eye have any effect on the success of laser surgery?
Yes. Not the color of the iris, but the more pigment on the trabecular meshwork, the better the response.
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© Robert Ritch, M.D., and Jeffrey M. Liebmann, M.D.
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Disclaimer: The authors provide no warranty. The information is provided to assist understanding of glaucoma. It does not replace an eye examination, and is not meant as a guideline for treatment of any individual person suffering from glaucoma. Your feedback is welcome.