SLT as Primary Treatment
In this retrospective study, the procedure lowered IOP in glaucoma patients by 35%.
BY LAWRENCE F. JINDRA, M.D.

As a laser treatment for glaucoma, selective laser trabeculoplasty (SLT) can be performed as primary treatment when a patient is first diagnosed with glaucoma, as adjunctive treatment to medications, or as an end-stage treatment to avoid surgery in a patient who is already on multiple medications.

SLT is performed with the Lumenis Selecta laser, a Q-switched frequency-doubled (532 nm) Nd:YAG laser that targets melanocytes in the pigmented trabecular meshwork. It disrupts the meshwork without causing thermal or coagulative damage to surrounding structures.

I've been performing laser trabeculoplasty as primary treatment since the mid-1990s, when multiyear results from the Glaucoma Laser Trial were published. That study demonstrated that in patients with newly diagnosed glaucoma the eyes initially treated with argon laser trabeculoplasty (ALT) had lower intraocular pressure and better visual field and optic disc status than their fellow eyes treated initially with topical medication. That convinced many glaucoma specialists to turn to laser therapy earlier.

We are now seeing a shift from ALT to SLT, which is proving to be equally or more effective, with less risk, fewer side effects, and better repeatability. I rely on SLT as primary therapy for all my glaucoma patients, except the occasional patient with active ocular inflammation. In those cases I temporize with medication until the inflammation quiets down, and then perform SLT.

I typically treat 240š during an initial SLT procedure, leaving the superior third of the eye untreated. Although I do this primarily because of my earlier ALT experience, it also makes filtering surgery easier, should it become necessary in the future.

Retrospective Chart Review

I recently conducted a retrospective chart review of 283 consecutive primary SLT cases and 43 consecutive repeat laser treatments in my practice between January 2002 and September 2003. The two patient populations were similar, although the repeat group was slightly older and had higher pre-SLT intraocular pressure (IOP). (See "Study Population and Results," above.)

In the primary treatment patients, IOP dropped from a mean of 21.1 mmHg (±4.7, range 13 to 48 mmHg) to 13.7 mmHg (±3.2, range 7 to 34 mmHg), a decrease of 35%.

One of the major differences between ALT and SLT is that one can see an immediate pressure reduction with SLT. After the initial plunge, there is typically a small increase back towards the pretreatment pressure. For example, in a patient with pretreatment IOP of 23 mmHg, one might see a reduction to 14 mmHg, then stabilization within a day or two at around 16 or 17 mmHg.

Fortunately, because of the method of action SLT employs, it can be repeated without decreasing the effectiveness of the procedure. This was demonstrated in the retrospective chart review. IOP also dropped by 35% in the retreatment arm of the study, from a mean of 23.7 mmHg (±6.5, range 12 to 42 mmHg) to 15.5 mmHg (±3.6, range 7 to 24 mmHg).

The incidence of complications, such as postoperative IOP spike, was less than 1/2% in each group.

Performance in the Retreatment Group

In the retreatment group, a second SLT procedure was performed in some cases because we did not reach the target pressure range with the first treatment. In other cases, SLT was done following previous ALT. A retreatment is no different from a primary procedure, although I sometimes will use a higher power setting in patients who under-responded to the initial SLT.

Because their pressure was not controlled by the first procedure, many of the patients in the study were also on IOP-lowering medications prior to the secondary procedure. After SLT, medication use fell by one-third, from an average of 1.48 medications per patient to 1.0.

On balance, I find that repeat SLT is far more effective than repeat ALT with less risk and fewer side effects. I would caution practitioners to wait at least 2 to 3 months before declaring an initial SLT procedure a failure, as some patients can be late responders.

Practice Patterns are Changing

Twenty-five years ago, our algorithm for glaucoma treatment was drop, drop, drop, pill, laser, surgery. Over the years, laser treatment has moved up in the algorithm. Ultimately, I think laser therapy (specifically SLT) will become the first-line treatment of choice for our glaucoma patients.

To date, I have seen no evidence in the scientific literature to suggest that laser will not work at least as well as, if not better than, medication as first-line therapy, nor have I seen any evidence that it leads to more complications.

In my clinical series, SLT significantly reduced IOP, by approximately 35%, in both primary and repeat treatments. Although further study in randomized clinical trials is needed, I personally will give the laser procedure a chance to fail before I will commit a patient to a lifetime of the cost, side effects, and added aggravation of topical glaucoma medications.

Dr. Jindra is founder and president of Floral Park Ophthalmology Associates in New York and assistant clinical professor of Ophthalmology at Columbia University's Edward S. Harkness Eye Institute. Contact him at drlfjind@optonline.net or (516) 616-1710. Dr. Jindra wishes to acknowledge contributions made to this study by Arusha Gupta and Sean Thomas, medical students at SUNY Stony Brook School of Medicine.