A discussion of efficacy, repeatability, safety, and cost.

Selective laser trabeculoplasty (SLT) is a unique therapy in glaucoma management. While almost all glaucoma therapies obey the rules that for each additional bit of pressure reduction, there must come a cost in terms of safety, SLT stands as a notable exception to the rule. This safe therapy is capable of significant pressure reductions, and it has been around for a long enough time to have accumulated a strong literature base demonstrating safety, efficacy, and versatility.

Despite its seeming Superman status in terms of data and the fact that SLT laser is used about 140,000 times annually, it is still nowhere close to being the primary therapy for patients with glaucoma.¹ SLT has obvious benefits in terms of tolerability, side-effect profile, cost (to patient, payer and physician) and compliance. To better understand how this paradox could exist, we attempt to bust open the myths that are holding back this unique therapy.

Myth 1: SLT doesn’t work.

The reality is that SLT has been shown in many studies to reduce intraocular pressure, delivering 25% to 40% pressure lowering.^2,3 Where does this myth come from? The myth likely stems from suboptimal usage of the laser. Many ophthalmologists, when using a new technology, will try it on very dramatic cases, such as a patient with wildly out-of-control glaucoma using 5 topical pressure lowering agents, with very advanced damage. SLT laser may not be able to completely fix that severe of a problem, just as traditional glaucoma surgery may also fall short. However, when SLT therapy is used in mild to moderate glaucoma or as primary therapy, the results are very different, and the literature backs this up.⁴ Studies have also shown a better response when the pressure is higher and the patient is treatment naïve. Similar to what we see in patients on medications, the lower the IOP to begin with, the less response you will see. Therefore, if you perform SLT on someone already on multiple drops, you may not obtain that 30% reduction seen in previous SLT studies.⁵

Myth 2: SLT must be repeated every few years.

Just because SLT can be repeated does not mean that it must be repeated, or that it should be repeated. Remember that argon laser trabeculoplasty was not repeatable, and thus it was nice to know that SLT could be repeated.⁶ Unfortunately, over time, some ophthalmologists took this to mean that the laser must be repeated. In fact, while repeatable, the laser has been shown to last for up to 5 years (and longer in my experience), without the need for a repeated procedure.⁷ When repeated, the laser will often last for several years as well.⁸ We should see the repeatability option as a positive feature of the laser, not as a necessary event that must be preplanned.

Myth 3: SLT is expensive and insurance companies don’t want to pay for it.

Given that SLT may last for years, it doesn’t take much effort to imagine how it would likely be less expensive than eye drops, particularly brand-name eye drops (but including generic drops). Lee and Hutnick found that any SLT laser still functioning 24 months after the procedure was cost effective, saving between $200 and $3,300 depending on how long it lasted and how many drops it replaced.⁹ A study by Seider et al demonstrated that SLT becomes less costly than most brand-name medications within 1 year and less costly than generic latanoprost and generic timolol after 13 and 40 months, respectively.¹⁰ Similarly, a 2012 study compared the cost of SLT to prostaglandin analogs in the treatment of newly diagnosed open-angle glaucoma.¹¹ The authors found that laser trabeculoplasty provided a cost saving of $2,645 per quality adjusted life year compared to prostaglandin analogs.

Obviously, the procedure is more profitable for physicians, who are reimbursed to do the laser, and it is also more profitable for the practice, which would likely be spending significant hours on phone calls to pharmacies to support any pharmacotherapy alternative to laser. Patients treated with the laser save time (spent obtaining and taking drops) and money (copays).

Myth 4: SLT isn’t as safe as drops.

In many FDA trials resulting in the approval of new glaucoma therapies, adverse events such as chronic eye redness or allergy occur in up to 30% of study patients. There is no lasting effect that occurs with such frequency with laser trabeculoplasty, and in fact experience will demonstrate that the laser has the capability of getting rid of eye-drop-related side effects such as dry eye and redness.

Until the recent approval of newer glaucoma medications such as latanaprostene bunod (Vyzulta; Bausch + Lomb) and netarsudil (Rhopressa; Aerie Pharmaceuticals), traditional glaucoma medications' mechanism of action as well as filtering surgery have been focused on areas outside of the natural outflow pathway (uveoscleral outflow or deceased aqueous humor production). Over time, the diversion of aqueous outflow through other pathways and decreased aqueous production can potentially further restrict the flow through the natural pathways.⁹ This is likely why we find SLT is most effective in an eye that has not received any medications yet.

Preserved drops (BAK containing) have the potential for preservative-induced toxicity and associated adverse effects. This can result in compromised ocular tolerance, patient discomfort, and decreased compliance. Patients who cannot tolerate the effects of preservatives may skip doses of preserved drops to avoid discomfort. They may discontinue medical therapy altogether. From the time the patients use drops, fibrosis is starting to occur on the surface. Preservatives can have toxic effects on the conjunctiva, therefore limiting the use of these medications may preserve the health of the conjunctiva which may be helpful in case future filtering surgery or tube surgery is needed. With SLT, we are essentially increasing the chance of surgical success.

Myth 5: SLT is meant for severe glaucoma, after all medical options have been exhausted.

The opposite is true. Studies, as exemplified in myth 1, demonstrate SLT works best in a naïve eye. In fact, the earlier the meshwork flow is addressed, the better chance we have of decreasing the progression of canal collapse and distal channel collapse.

Myth 6: Most physicians would not want “laser first” if it were their own eye.

Actually, about half of ophthalmologists would prefer laser first, but when it comes to treating patients, only 10% of patients are treated with laser first, which tells us that we are not living up to our own standards in terms of delivering laser. Physicians may be hesitant to recommend laser first because they are concerned it is a departure from the standard of care - it isn't. GP

References

1. Arora KS, Robin AL, Corcoran KJ, Corcoran SL, Ramulu PY. Use of various glaucoma surgeries and procedures in medicare beneficiaries from 1994 to 2012. Ophthalmology. 2015;122(8):1615-1624.
2. Latina MA, de Leon JM. Selective laser trabeculoplasty. Ophthalmol Clin North Am. 2005;18(3):409-419.
3. Katz LJ, Steinmann WC, Kabir A, Molineaux J, Wizov SS, Marcellino G; SLT/Med Study Group. Selective laser trabeculoplasty versus medical therapy as initial treatment of glaucoma: a prospective, randomized trial. J Glaucoma. 2012;21(7):460-468.
4. Realini T. Selective laser trabeculoplasty for the management of open-angle glaucoma in St. Lucia. JAMA Ophthalmol. 2013;131(3):321-327.
5. Mao AJ, Pan XJ, McIlraith I, Strasfeld M, Colev G, Hutnik C. Development of a prediction rule to estimate the probability of acceptable intraocular pressure reduction after selective laser trabeculoplasty in open-angle glaucoma and ocular hypertension. J Glaucoma. 2008;17:6:449-454. 
6. Polat J, Grantham L, Mitchell K, Realini T. Repeatability of selective laser trabeculoplasty. Br J Ophthalmol. 2016;100(10):1437-1441.
7. Patel V, El Hawy E, Waisbourd M, et al. Long-term outcomes in patients initially responsive to selective laser trabeculoplasty. Int J Ophthalmol. 2015;8(5):960-964.
8. Khouri AS, Lari HB, Berezina TL, Maltzman B, Fechtner RD. Long term efficacy of repeat selective laser trabeculoplasty. J Ophthalmic Vis Res. 2014;9(4):444-448.
9. Lee R, Hutnik CM. Projected cost comparison of selective laser trabeculoplasty versus glaucoma medication in the Ontario Health Insurance Plan. Can J Ophthalmol. 2006;41(4):449-456.
10. Seider MI, Keenan JD, Han Y. Cost of selective laser trabeculoplasty vs topical medications for glaucoma. Arch Ophthalmol. 2012;130:529-530.
11. Stein JD, Kim DD, Peck WW, et al. Cost-effectiveness of medications compared with laser trabeculoplasty in patients with newly diagnosed open-angle glaucoma. Arch Ophthalmol. 2012;130:497-505.

Inder Paul Singh, MD, is a glaucoma specialist at the Eye Centers of Racine and Kenosha, in Wisconsin. Dr. Singh reports financial relationships with Ellex, Alcon, Allergan, New World Medical, Bausch + Lomb, Shire, Aerie, and Sun Ophthalmics. Reach him at ipsingh@amazingeye.com.

Nate Radcliffe, MD, is a clinical assistant professor in the department of ophthalmology at the New York Eye and Ear Infirmary and a surgeon at the New York Eye Surgery Center. Dr. Radcliffe reports consultancy to Aerie Pharmaceuticals, Lumenis, Iridex, Ellex, and Bausch + Lomb. Reach him at drradcliffe@gmail.com.