June 03, 2019
4 min read

Ophthalmologists may want to offer SLT at earlier time

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Argon laser trabeculoplasty was first presented to ophthalmologists by Wise and Witter in 1979. ALT found a place in clinical practice after drops and before surgery. Twenty years later, in 1999, Mark Latina, MD, reported his initial results with selective laser trabeculoplasty. SLT uses a frequency-doubled 532 nm Q-switched Nd:YAG laser rather than an argon laser.

The amount of energy applied to the trabecular meshwork with SLT is about 1% of that applied in ALT. The SLT laser pulse duration is only 3 nanoseconds. The spot size is always 400 µm. The power is variable, with as low as 0.3 mJ being effective in the heavily pigmented trabecular meshwork and as much a 1.0 mJ required in lightly pigmented trabecular meshwork. SLT has become more popular as it is easier to perform and causes less tissue damage in the trabecular meshwork. Typically, about 100 spots are placed over the full 360° of trabecular meshwork, but some studies suggest that similar outcomes can be obtained when treating only 180°.

There is a CPT code, 65855, and Medicare and most commercial payers reimburse for SLT. Office reimbursement by Medicare is about $340. If the procedure is done in an ASC, surgeon reimbursement is reduced to about $300 and a facility charge of about $190 allows a total fee of $490. As usual, when done in a hospital, the facility fee is higher, about $445, bringing the total in-hospital cost to $745. Most of us do the procedure in the office or ASC so the cost to Medicare is $340 to $490. There is a 10-day global period in which postoperative care is included in the fee.

Most surgeons apply one drop of apraclonidine or brimonidine before or after treatment to reduce pressure spikes. A few use low-dose pilocarpine. Postoperative treatment with a 4- to 7-day course of topical steroid is optional. The most common postoperative adverse events are transient iritis and pressure spikes. Many surgeons hold their patients in the office for 1 hour for an IOP check. More serious side effects can occur, including hyphema, cystoid macular edema and even choroidal effusion, but they are rare.

The IOP-lowering effect for primary open-angle glaucoma in a meta-analysis reviewing 10 series ranged from 5 mm Hg to 9 mm Hg, which represented a 22% to 30% reduction from preoperative pressures. The pressure-lowering effect is slowly lost over time, with about a 50% reduction at 5 years, or 10% per year. The treatment can be repeated with good effect.


Right from the beginning SLT was suggested as a first-line alternative to topical medical therapy for glaucoma. The efficacy of SLT is quite similar to the efficacy of a prostaglandin analogue such as generic latanoprost given once at bedtime. A 1-month supply of generic latanoprost in Minneapolis costs about $12, so a year of therapy is $144. If the SLT is done in the office, it is likely less expensive to both the third-party payer and patient by the third year but of course more expensive at the downstroke.

SLT is especially attractive when we consider patient adherence or compliance, which is usually poor. In the Gazzard study discussed in the accompanying cover story, starting new glaucoma patients with SLT rather than drops resulted in better IOP control, less progressive glaucoma damage and less need for rescue trabeculectomy. As a clinician, looking at the data objectively, it is easy to conclude that we could/should start with SLT rather than a topical drop when initiating therapy for ocular hypertension or first-diagnosed POAG. But most of us do not, and in full disclosure, I do not.

In giving this some thought, I believe it is because patients and, arguably, most doctors find the idea of first trying an inexpensive topical drop once a day quite attractive. No matter how I present it, as a minimally invasive laser surgery, a laser procedure, an office laser treatment or even just a same day walk down the hall treatment, most patients perceive SLT as being more invasive, more expensive and a bigger deal than taking one drop a night before bedtime.

However, the accumulating evidence is convincing that SLT should be offered as a first-line alternative to every newly diagnosed glaucoma patient followed by a discussion of the relative risks, benefits, alternatives and costs of SLT vs. drops. Starting now, I intend to do just that with more conviction than I have in the past, but in my heart, I still expect most of my patients will choose to start with a drop of generic latanoprost at bedtime. If they are not well controlled, I will discuss the SLT option again before starting them on a second bottle of drops. In my practice, no glaucoma patient ever receives more than two bottles, as full medical therapy is available with a two-bottle regimen utilizing commercial and compounded formulations in combination.

Today, in my practice SLT is mostly applied to patients who progress despite two bottle/four active pharmaceutical agent therapy or who prove themselves nonadherent to my recommended medical regimen. However, another review of the literature reinforced by this recent well-performed study in England and published in The Lancet has convinced me I may not be offering SLT as frequently as I should. I will be offering SLT to my glaucoma patients as an alternative to drops at the earliest stage and every time I add an additional topical therapeutic agent. It will be interesting to see how many of my patients select it. If the preference for drops over SLT is patient driven, my practice will not change. But if patients would really prefer a minimally invasive office laser treatment over drops, SLT will be a bigger part of my practice in a year. Time will tell.

Disclosure: Lindstrom reports relevant financial disclosures for Ellex and Belkin Laser.