Introduction

High eye pressure in conditions like open-angle glaucoma or ocular hypertension can damage vision over time. Traditionally, doctors start treatment with daily medication drops to lower intraocular pressure (IOP). However, Selective Laser Trabeculoplasty (SLT) is a one-time laser treatment that safely opens the eye’s drainage angle to help fluid escape and lower IOP (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Recent large studies show that using SLT first can achieve similar pressure control as drops, while many patients avoid needing drops at all (pmc.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov). This can reduce the hassle and side effects of medications.

Evidence for SLT as First-Line Therapy

The LiGHT Trial (SLT vs Drops)

The pivotal LiGHT trial (Lancet 2019) compared first-line SLT to eye drops in newly diagnosed glaucoma/ocular hypertension patients (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Over 3 years, both groups reached their pressure targets equally well, but 74% of the SLT-first patients needed no drops at all to maintain control (pmc.ncbi.nlm.nih.gov). In other words, about three out of four patients on SLT alone stayed at target pressure without ongoing medications for at least three years (pmc.ncbi.nlm.nih.gov). By contrast, patients started on drops needed those medications continuously. Importantly, eye pressure was within target slightly more often in the SLT-first group (93% of visits) than the drops group (91%) (pmc.ncbi.nlm.nih.gov). None of the SLT-first patients required glaucoma surgery, whereas 11 patients in the drops group did. The trial also found SLT to be highly cost-effective – saving healthcare costs by reducing surgeries and medications (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).

Other Randomized Trials

Another randomized trial with treatment-naïve glaucoma patients (the Glaucoma Initial Treatment Study) found that both SLT and drops effectively lowered IOP (pubmed.ncbi.nlm.nih.gov). Over 24 months, medication slightly edged out SLT in the rate of achieving a 25% IOP drop, but those on drops experienced more eye redness and eyelid irritation (pubmed.ncbi.nlm.nih.gov). Quality of life measures were similarly improved in both groups (pubmed.ncbi.nlm.nih.gov). In summary, trials show SLT matches medication in lowering IOP and often spares most patients from daily drops (pubmed.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).

Who Benefits Most from SLT First?

Deciding who should get SLT first depends on individual factors. Research has identified several predictors of SLT success:

• Baseline eye pressure (IOP): Patients with higher initial IOP generally see a larger pressure drop after SLT. In one study, eyes with baseline IOP >18 mmHg saw an average 23.7% drop, whereas eyes with lower starting IOP had almost no change (pmc.ncbi.nlm.nih.gov). This means patients with very high eye pressure tend to benefit more from SLT.
• Trabecular meshwork pigmentation: The drainage area (trabecular meshwork) often has pigment. Some studies suggest heavily pigmented angles may respond more strongly to SLT. For example, patients with high angle pigmentation had about a 4.8 mmHg average pressure drop, versus ~2.1 mmHg in lightly pigmented eyes (pmc.ncbi.nlm.nih.gov). However, other research indicates SLT still works in low-pigment eyes and that pigment may mainly affect the risk of a brief post-laser pressure spike (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). In practice, heavy pigmentation can lead to a strong effect but also requires careful monitoring right after the procedure.
• Other factors: Some reports link older age, certain glaucoma types (like exfoliation or pigmentary glaucoma), or needing many types of drop medications with a better SLT response (pmc.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov). Also, a patient’s response in one eye often predicts the other eye’s outcome (pubmed.ncbi.nlm.nih.gov).

Overall, nearly all types of open-angle glaucoma can see IOP reduction with SLT (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Patients with elevated pressure and difficulty using drops at home often get the most benefit.

SLT Retreatment and Durability

How Long Does SLT Last?

SLT’s pressure-lowering effect typically starts within weeks and can last 1–2 years or more. In practice, many patients enjoy lower pressure for up to 2–3 years before needing another intervention. For those on SLT first in the LiGHT trial, about 74% stayed controlled without drops for three years (pmc.ncbi.nlm.nih.gov). On average, the pressure benefits can persist 1–2 years or longer.

Repeating SLT

When pressure rises again, SLT can safely be repeated. Studies show that a second or third SLT can achieve additional pressure lowering. For example, one report of 52 patients found that first, second, and third SLT treatments each produced about a 26–27% IOP drop, and the time until pressure wandered upward increased after repeat treatments (pubmed.ncbi.nlm.nih.gov). Interestingly, the second SLT often lasted even longer (over 33 months on average) than the first (22 months) (pubmed.ncbi.nlm.nih.gov).

Other research agrees that repeating SLT works: a repeat SLT yielded similar success rates (>20% IOP drop) as the first treatment (pubmed.ncbi.nlm.nih.gov). In that study, eyes needing a second SLT could be retreated as early as 6 months after the first. Generally, if an initial SLT eventually wears off, a doctor may offer another SLT rather than surgery or more medications (pubmed.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov). Each repeat SLT carries about the same safety and side-effect profile: mild, short-term redness or discomfort can occur, but there’s no cutting or incisions.

Cost-Effectiveness

SLT can be very cost-effective compared to years of eye drops. The LiGHT trial included a detailed economic analysis and found that SLT-first costs less overall. Over 3 years, patients in the drops-first group spent on average £465 more on medication than those in the SLT-first group (pmc.ncbi.nlm.nih.gov). In fact, starting with laser led to net savings (all costs considered, including fewer surgeries) of roughly £450 per patient over three years (pmc.ncbi.nlm.nih.gov). Nearly all health-economic models agree: SLT pays for itself in 1–3 years, depending on drop prices (pmc.ncbi.nlm.nih.gov). If SLT is repeated within 3 years as needed, it remains more cost-effective than multiple medications (pmc.ncbi.nlm.nih.gov).

From a patient’s perspective, SLT means fewer prescription costs and fewer clinic visits to manage side effects. Many patients also appreciate avoiding the daily chore of eye drops. On a system level, widespread use of SLT first could save significant healthcare resources while providing equally good control (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).

Deciding SLT First vs Medication

Choosing whether to start with SLT or medication involves both clinical factors and patient preferences. Here is a simplified decision guide:

• Diagnosis: You have confirmed open-angle glaucoma or ocular hypertension (high pressure without nerve damage).
• Patient factors:
  • Compliance: Are you likely to reliably use daily drops? If you struggle with remembering or have trouble with eye drops, SLT can remove that burden (pubmed.ncbi.nlm.nih.gov).
  • Preferences: Do you prefer a one-time procedure over daily drops? Some patients favor laser to avoid ongoing treatment.
  • Side effects: If past experience with drop side effects (red eyes, eyelid changes, etc.) has been bad, SLT avoids those.
• Clinical factors:
  • Baseline IOP: If your starting eye pressure is high, SLT may achieve a strong lowering effect (pmc.ncbi.nlm.nih.gov).
  • Angle status: SLT only works for open-angle glaucoma. If your drainage angle is too narrow or abnormal, drops or surgery might be safer first.
  • Stage of glaucoma: For mild-to-moderate cases, SLT first is often fine. In very advanced cases needing very low targets ASAP, a combination of treatments might be needed.
  • Glaucoma type: SLT can benefit most types (exfoliation, pigmentary glaucoma, etc.), but if your eye has very heavy pigment or pseudoexfoliation, inform your doctor as they may watch closely for pressure spikes after laser.
• Previous treatment: If you’ve already been on drops and pressure is still high, adding or switching to SLT is a good next step (this is well-supported and safe).

A typical decision flow might look like:

• Diagnosis of glaucoma/ocular hypertension confirmed.
• Are your angles open and visible?
  • Yes: SLT is an option.
  • No: Consider eye drops or other surgery.
• Do you have trouble with drops (cost, side effects, adherence)?
  • Yes: Lean toward SLT first (pubmed.ncbi.nlm.nih.gov).
  • No: Both options are viable.
• Is your target pressure very low (e.g. aggressive disease)?
  • Yes: Some doctors may start drops or combine SLT+drops for faster effect.
  • No: SLT alone is reasonable.
• Patient choice: After discussing pros and cons, decide with your doctor whether to try SLT first or to start with drops.

In all cases, close follow-up is important. If SLT is chosen first and later pressure is not low enough, drops can always be added or the laser repeated. If medication is started first and proves insufficient or bothersome, SLT can be done later with similar benefit (pubmed.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov).

Conclusion

Selective Laser Trabeculoplasty is an effective, safe first-line option for many patients with open-angle glaucoma or ocular hypertension. Large trials have shown it can match medication in lowering pressure and often eliminates the need for daily drops for years (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Patients with higher baseline IOP and open, pigmented angles tend to see the best drops from SLT (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Importantly, SLT has a low risk of side effects, can be repeated when needed, and has proven cost savings compared to long-term medications (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). When choosing first-line therapy, factors like your glaucoma severity, eye anatomy, lifestyle, and preference should guide the decision. Discuss with your doctor whether starting with SLT or with drops makes the most sense for you. In many cases, SLT as initial therapy offers long-lasting control and greater convenience for the patient (pmc.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov).