Selective laser trabeculoplasty (SLT) was introduced as a safe, effective treatment for primary open-angle glaucoma (POAG) more than 20 years ago, and researchers have since touted it as not just a tool to stave off glaucomatous damage, but as a first-line therapy, even before drops, for many patients. Despite research into its safety and efficacy, though, it is still not the front-line therapy of choice for many physicians.1 Recently, a Philadelphia-based research team sought to understand why the procedure suffers from lack of adoption, and offer their suggestions for boosting SLT’s acceptance in the field.

Glaucoma is likely to affect more than 3 million Americans this year alone.2 Reducing intraocular pressure (IOP) is the only modifiable risk factor known to manage the disease, whether that’s accomplished via pharmacological treatment, laser therapy, or surgical interventions.2 SLT’s efficacy as an initial and adjunctive therapy has been confirmed through peer-reviewed research.2 Its predecessor, argon laser trabeculoplasty (ALT), could damage the trabecular meshwork, saw more reported adverse events, and had worse repeatability than SLT.1 Additionally, SLT can reduce or, in some cases, eliminate the need for topical medications.1 This makes it a viable treatment option for patients who cannot tolerate medications due to side effects, have trouble applying drops, or who are unable to undergo surgery. For many, the procedure is simply a more economical option than eye drops or surgery.1,3 

A 2019 study shows that a lower percentage of patients treated with SLT first experienced disease progression than patients treated with medicine first.4 In a post-hoc analysis of that study, 74.6% of eyes (400 eyes) treated with primary SLT achieved drop-free disease-control at 3 years follow-up, of which 58.2% (312 eyes) required only one SLT treatment.1


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Beliefs and Attitudes About SLT

In a study published in Glaucoma, researchers hypothesized that the disconnect between SLT’s documented efficacy and its rate of adoption may be related to a lack of understanding and a misconceived belief that eye drops are a less invasive initial treatment option.

To test this, the investigators — including Lucas Bonafede, MD, and L. Jay Katz, MD — developed an educational video designed to clear up any confusion with regards to prescribing SLT for patients earlier in the treatment continuum. A group of 53 ophthalmologists, ophthalmology residents, and glaucoma specialists were asked to complete a questionnaire regarding their beliefs and attitudes about SLT before and after watching the video.

Before watching the video, approximately half (52%) of the physicians reported that their newly diagnosed patients receive laser therapy and only 47% said they would use it as first-line therapy for all or most newly diagnosed glaucoma patients.2 While 85% of the doctors said they offer SLT to newly diagnosed patients, only 28% said they preferred it to medications.2 

However, after watching the video, most clinicians (94%) reported that the presentation convinced them that SLT is appropriate as a first-line therapy.2 Safety, efficacy, and adherence were the main reasons why clinicians supported the use of SLT.2 Despite this, nearly a third (32%) of study participants said they were still hesitant to prescribe it as first-line therapy, with patient hesitation and limited experience leading the list of deterrents.2

Misplaced Caution

Ophthalmologists determine treatment based on the severity of the patient’s condition, the disease’s rate of progression, and the impact of symptoms on the patient’s quality of life.2 Among study participants who indicated that they would use SLT as a first-line therapy, good compliance (64%) and efficacy (60%) were the top reasons for utilization.2 SLT works best when it’s used as first-line therapy, says Dr. Katz, but most ophthalmologists use SLT as an adjunctive therapy. The procedure’s success rate as a second or third treatment is typically lower than when SLT is used as a first step.2 

Dr. Katz notes that while glaucoma medications are often believed to be a less aggressive treatment modality, there are potential side effects. Topical medications can cause itchiness, redness, and blurred vision. Compliance is an issue, and paying for medications also can be problematic.

In SLT, the patient’s melanin granules in the trabecular meshwork are heated selectively by the laser, while sparing the surrounding tissue, explains Dr. Bonafede. This “rejuvenates an aging drainage system” to improve the flow of fluids.

“I don’t understand why there is a resistance to SLT,” says Priya Desai, MD, MDA, a glaucoma subspecialist at Matossian Eye Associates in Hopewell, NJ, when asked about the study. “The conservative line of thought is that we do procedures only after we have gone the pharmaceutical route. Procedures are viewed as an escalation in care and a more aggressive form of treatment than pharmaceutical agents, but I disagree. Pharmaceutical agents can cause a lot of quality-of-life issues for patients.”

Dr. Desai cites burning, redness, irritation, cost, and compliance as issues related to prescribing drops. She’s also found that patients with medical conditions such as Alzheimer disease or arthritis have struggled to administer drops consistently.

Clinical Concerns

Patient hesitancy (32%), patient selection (29%), lack of evidence (21%), and availability (21%) were the top reasons for not endorsing SLT as first-line therapy in Drs. Bonafede and Katz’s research.2

While most studies have reported that SLT is highly successful at reducing IOP, some findings suggest that the results of the procedure are unpredictable.1 Failure rates of up to 60% have been reported, with factors such as patient population, type of glaucoma, SLT treatment protocol, and surgeon factors accounting for the inconsistency in efficacy.1 Further, the effect of SLT has been reported to decrease over time.1 While the procedure will likely need to be repeated, the benefit decreases with each round of treatment in most cases. Long-term studies beyond 5 years have suggested that a significant proportion of SLT-treated eyes may eventually require further medications or surgical interventions.1

The procedure also carries some risk of complication, including iritis, IOP spikes, and corneal damage — factors that may deter some ophthalmologists from offering SLT as a first-line treatment.1 Other factors that may be impacting its acceptance include surgeon experience, medico-legal considerations, and logistical issues, such as access to laser facilities.1

If the laser isn’t aimed properly, it can cause inflammation, macular swelling, scarring, or corneal changes, according to Dr. Desai. And while the technology can be cost-prohibitive for some practices, she said there are ways to decrease the capital expense, such as renting a mobile unit or purchasing a machine that can be used to perform other procedures in addition to SLT.

“I don’t push my patients to use the laser because it’s not more effective than eye drops — they’re about equal in efficacy when used first — but I present the pros and cons of both options to every patient. About 60% choose the laser and are happy with the results,” Dr. Desai explains.

In fact, research does show comparable results between SLT and topical drops. Dr. Katz authored such a study that found similar efficacy between the two as initial therapy.5 That research, published in 2012, took into account 127 eyes with either POAG or ocular hypertension. The participants were randomized into groups based on whether they underwent SLT or a prostaglandin analogue treatment. At 1-year, the SLT patients saw a 6.3 mm Hg reduction in IOP and the medication group saw a 7 mm Hg reduction. Of the SLT patients, 11% received additional treatments, while 27% of the prostaglandin group required additional prescriptions.5

Improving Adoption

Inexperience was cited by 75% of general ophthalmologists as the reason for their reluctance.2 Availability was also cited as a deterrent among the general ophthalmologist population. “Increased targeted education toward general ophthalmologists will improve their understanding and adoption of SLT,” insists Dr. Katz. “With increased understanding, SLT will be more sought-after and availability will improve.”

“My hope is that, with the rejuvenated interest in SLT, and as new ophthalmologists in training become more exposed to SLT we will progress to accept it and offer it as a possible first-line therapy,” says Dr. Bonafede.

Drs. Bonafede and Katz noted a few limitations to their study, including the low response rate to the questionnaire and the study’s small subject pool, which was primarily from a single institution. Additionally, the study was descriptive with no direct follow-up on practice patterns, so it’s unclear if the reported changes in attitudes translated to actual changes in physicians’ practice. Lastly, the preintervention

and postintervention questionnaires were not identical, which hampered the ability to interpret the response to the educational video.

Ultimately, the plan of care for newly diagnosed POAG patients should be a discussion between the surgeon and his or her patient. By outlining the risks, benefits, cost, and impact on quality of life for each option, physicians will better inform patients about their treatment choices.

References

1. Ang M, Tham CC, Sng CCA. Selective laser trabeculoplasty as the primary treatment for open angle glaucoma: time for change? Eye. 2020;34(10);789–791. doi:10.1038/s41433-019-0625.

2. Bonafede L, Sanvicente CT, Hark LA, et al. Beliefs and attitudes of ophthalmologists regarding slt as first line therapy for glaucoma. J Glaucoma. 2020;29(10):851-856. doi: 10.1097/IJG.0000000000001615. 

3. Yong MH, Hamzah JC. Selective laser trabeculoplasty vs. topical medications for step-up treatment in primary open angle glaucoma: comparing clinical effectiveness, quality of life and cost-effectiveness. Med J Malaysia. 2020;75(4):342-348.

4. Gazzard G, Konstantakopoulou E, Garway-Heath D, et al. Selective laser trabeculoplasty versus eye drops for first-line treatment of ocular hypertension and glaucoma (LiGHT): a multicentre randomised controlled trial. The Lancet. 2019;393(10180):1505-1516. doi:10.1016/S0140-6736(18)32213-X. 

5. Katz J, Steinmann W, Kabir A, Molineaux J, Wizov S, Marcellino G. Selective laser trabeculoplasty versus medical therapy as initial treatment of glaucoma: a prospective, randomized trial. J Glaucoma. 2012;12(7):460-468.