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Hashemi Eye Care - Neuroscience Institute and Research Center

Selective Laser Trabeculoplasty (SLT)

A laser treatment that lowers eye pressure in glaucoma by improving the eye's natural drainage. Learn what to expect from this safe, effective procedure.

6 min read

Selective laser trabeculoplasty (SLT) is a laser procedure that lowers eye pressure in open-angle glaucoma by improving fluid drainage through the eye's natural drainage system (trabecular meshwork). It's safe, effective, and increasingly used as a first-line treatment for glaucoma.

Key Takeaways

  • Lowers eye pressure by improving natural drainage
  • Can be first-line treatment instead of eye drops
  • Quick, in-office procedure—about 5-10 minutes
  • Generally painless with minimal recovery
  • Can be repeated if effect wanes over time
  • Not effective for angle-closure glaucoma

How SLT Works

The Drainage System

Aqueous humor (fluid inside the eye) drains through the trabecular meshwork—a spongy tissue at the angle where the iris meets the cornea. In open-angle glaucoma, this drainage becomes less efficient.

Laser Effect

SLT uses short pulses of low-energy laser light to:

  • Target pigmented cells in the trabecular meshwork
  • Stimulate a biological response
  • Recruit the body's own cells to improve drainage
  • Increase fluid outflow and lower eye pressure

"Selective" means it targets only pigmented cells, leaving surrounding tissue undamaged. This is why SLT can be safely repeated.

Who Is a Candidate

Good Candidates

Not Candidates

  • Angle-closure glaucoma—drainage angle blocked
  • Neovascular glaucoma
  • Inflammatory glaucoma (uveitic glaucoma)
  • Previous failed SLT (though repeat is sometimes tried)
  • Very advanced glaucoma needing more aggressive treatment

SLT vs. Eye Drops

Factor SLT Eye Drops
Effectiveness ~80% respond, average 20-30% IOP reduction Varies by drug class
Compliance One-time procedure Daily, lifelong
Side effects Minimal, temporary Various (burning, redness, systemic effects)
Cost Single cost Ongoing expense
Repeat needed May need repeat in 3-5 years Ongoing

Many patients choose SLT first, adding drops only if needed.

The Procedure

Before SLT

  • No special preparation
  • Continue regular medications
  • Arrive at appointment normally
  • Procedure takes about 30 minutes total (including prep)

During SLT

What happens:

  1. Numbing drops placed in the eye
  2. Special lens placed on eye (like gonioscopy)
  3. Laser applied to trabecular meshwork (50-100 spots)
  4. You may see flashes of light
  5. Duration: 5-10 minutes per eye
  6. Most patients feel little to nothing; some feel mild discomfort

After SLT

  • May have mild discomfort, redness, or blurry vision temporarily
  • Anti-inflammatory drops usually prescribed for a few days
  • Can resume normal activities same day
  • Driving usually fine (ask your doctor)
  • Follow-up appointment in 4-6 weeks to check pressure

Results and Expectations

Effectiveness

  • Success rate: ~80% of patients see meaningful pressure reduction
  • Average reduction: 20-30% lower IOP
  • Maximum effect: Usually within 4-8 weeks
  • Duration: Typically lasts 3-5 years (varies widely)

What Success Looks Like

  • Reduced eye pressure
  • May reduce or eliminate need for drops
  • May slow glaucoma progression
  • Some patients still need drops in addition to SLT

When Effect Wanes

The effect of SLT gradually decreases over years:

  • Can repeat SLT (one advantage over older laser)
  • May need to add eye drops
  • May consider surgery if pressure uncontrolled

Risks and Side Effects

Common (Temporary)

Uncommon

  • Inflammation requiring extended treatment
  • Persistent pressure spike
  • Corneal haze

Rare

  • Significant pressure spike requiring intervention
  • Rarely, peripheral anterior synechiae (scarring)

Contact your doctor if you experience:

  • Significant eye pain after procedure
  • Markedly decreased vision
  • Increasing redness after first day
  • Severe headache with eye symptoms

SLT vs. ALT

SLT replaced an older procedure called ALT (argon laser trabeculoplasty):

Feature SLT ALT
Energy Low High
Tissue damage Minimal More scarring
Repeatability Can repeat Limited
Effectiveness Similar Similar
Preference Current standard Rarely used now

Frequently Asked Questions

Does SLT hurt?

Most patients experience little to no pain. You may feel a slight sensation during the laser application, and some mild aching afterward that resolves within hours.

How long does SLT last?

The effect typically lasts 3-5 years, though this varies. Some patients maintain effect longer; others may need repeat treatment or additional therapy sooner.

Can SLT cure my glaucoma?

No. SLT controls eye pressure but doesn't cure glaucoma. Ongoing monitoring is essential. The underlying condition remains and may progress if pressure isn't adequately controlled.

Will I still need eye drops after SLT?

Some patients can stop drops entirely. Others need fewer drops or lower doses. Some still require the same medications but have better pressure control. Your doctor will assess your response.

Can SLT be repeated?

Yes, SLT can generally be repeated if the effect diminishes. This is a key advantage over the older ALT procedure. However, repeated treatments may have diminishing returns.

Is SLT better than eye drops?

For many patients, yes—SLT offers comparable pressure reduction without daily drops. Major studies (like LiGHT trial) found SLT as first-line treatment kept more patients off drops and was cost-effective. However, individual situations vary.

How soon can I see results?

Pressure typically starts to lower within 1-2 weeks, with maximum effect by 4-8 weeks. A follow-up visit will assess your response.

Can I have SLT on both eyes at once?

Doctors vary in practice. Some treat one eye at a time to assess response; others may treat both eyes in certain situations. Your doctor will discuss the plan.

References

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