August 22, 2018 | POSTED BY | Clinical Optometry, Clinical Pearls
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A patient sits down in your chair being followed for possible glaucoma. You have determined they have a progressing C/D ratio and, after running an OCT and visual field, your attending and you decide that they have a thinning RNFL and suspicious visual field defect. You discuss with the patient that it is time to begin treatment. The next question is obvious: which treatment are you going to recommend? Topical prostaglandins or beta blockers are no longer the only first line treatment options. Recent studies have shown that selective laser trabeculoplasty (SLT) is comparable in efficacy to starting patients on a topical prostaglandin analogue, such as latanoprost (1). Of course, before we recommend a laser surgical procedure to our patients, we need to know what we are talking about.

Open Angle GlaucomaSLT is used to treat multiple forms of open angle glaucoma and ocular hypertension. The SLT laser is made up of a Q-switched 532 nanometer frequency-doubled Nd:YAG laser (see picture to left) that puts off 400 micrometer, 3 nanosecond pulses into the trabecular meshwork (TM) (2).  The laser is selective for the pigmented TM cells, hence its name. Currently, the main theory on SLT is that these energy pulses cause stress within the pigmented TM, causing an influx of inflammatory cells such as macrophages to come “clean up” the TM by clearing out the pigment that is blocking aqueous outflow, thus decreasing resistance. This lowers the intraocular pressure (IOP), which we know is currently the only modifiable risk factor in the prevention of glaucoma progression.

So why exactly would you recommend your patient for surgery instead of starting them on drops? There are, of course, many factors that go in to putting a patient on any treatment; however, SLT offers a few definite perks for the patient.

  1. Compliance. Aside from the IOP lowering being comparable to treating a patient with a topical hypotensive drop, SLT lowers patient compliance issues by delaying the need for drops or decreasing the amount of drops that need to be put in daily. We know that compliance with glaucoma patients is of real concern. One study showed that less than 50% of patients with glaucoma used their drops correctly for even one year (1). After SLT, if a patient’s need for drops is eliminated, the risk of non-compliance is essentially zero during the duration of efficacious pressure control after the procedure. This decrease in pressure typically lasts 1-3 years (although shorter and longer control are possible). Repeat SLT is shown to have some efficacy it diminishes with time, and patients should be educated that re-initiating or adding drops in the future is likely.
  2. Side effects. Patients on hypotensive topical drops often complain of various side effects associated with the medication. Some of the most common side effects include hyperemia, burning, dry eye, and foreign body sensation. Other less common side effects include eyelid and iris pigmentation, periorbital fat loss, and lash growth, in addition to potential systemic side effects of drops such as the topical beta blockers. Choosing to recommend SLT, especially as a first line treatment, keeps your patients from having to deal with these daily side effects.
  1. Cost. Some studies show that the cost of treating patients with SLT is comparable to adherent generic drop-users, if not actually more cost-effective (1,3). Because glaucoma is a chronic disease that will need to be treated for life, holding off on beginning daily drops can end up saving the patient money over time. Obviously, this is something that is very important to our cost-conscious patients.

    Open Angle Glaucoma on gonioscopic view

    Gonioscopic view of laser targeting pigmented TM in a patient with primary open angle glaucoma

Overall, SLT offers many benefits to our glaucoma patients, especially those that are newly diagnosed. Patients no longer need to have tried drops to be considered for this procedure (1). The first step to pursuing this line of treatment is talking with your patient about the benefits of the procedure and understanding its effectiveness as a first line treatment. With its potential to be repeated,  SLT can, in some situations, help hold off your patient’s need for drops for years and that is worth considering!

References: 

  1. Waisbound M, Katz LJ. Selective laser trabeculoplasty as a first-line therapy: a review. Can J Ophthalmol 2014;49:519-22.
  2. Keyser MD, Belder MD, Belder JD, Groot VD. Selective laser trabeculoplasty as replacement therapy in medically controlled glaucoma patients. Acta Opthalmol 2017;10:1-5.
  3. Stein JD, Kim DD, Peck WW, Giannetti SM, Hutton DW. Cost effectiveness of medications compared with laser trabeculoplasty in patients with newly-diagnosed open-angle glaucoma. Arch Ophthalmol 2012;130:497-505.

Thank you to the Northeastern State University Oklahoma College of Optometry for use of photos and Dr. Jeff Miller for contributing suggestions to improve this article.