Selective Laser Trabeculoplasty (SLT)

Selective laser trabeculoplasty (SLT) is an office laser that helps the eye's natural drain, the trabecular meshwork, move fluid out more efficiently. Lower pressure means less stress on the optic nerve in open-angle glaucoma. SLT is increasingly used early, sometimes before daily drops, because it can reduce medication burden for appropriate patients.

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 the laser targets pigmented cells in the drainage tissue with little structural damage around them. That is why SLT can often be repeated, unlike older, more scarring laser approaches.

Who Is a Candidate

Good Candidates

• Primary open-angle glaucoma (POAG)
• Normal-tension glaucoma
• Ocular hypertension (elevated pressure without damage)
• Patients who want to avoid or reduce eye drops
• Those struggling with drop side effects or adherence
• Pseudoexfoliation glaucoma
• Pigmentary glaucoma

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

Many patients choose SLT first, adding drops only if needed. That said, if the glaucoma is advanced and the pressure needs to be very low, drops or surgery may still be part of the plan.

The Procedure

Before SLT

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

During SLT

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

• Response rate: many studies report meaningful pressure reduction in roughly 70-80% of appropriate patients
• Average reduction: often about 20-30% from baseline IOP
• Maximum effect: usually within 4-8 weeks
• Duration: commonly 3-5 years, but the spread is wide

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)

• Mild discomfort or aching (few hours)
• Eye redness
• Blurry vision (clears within hours to days)
• Light sensitivity
• Temporarily elevated eye pressure

Uncommon

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

Rare

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

SLT vs. ALT

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

Frequently Asked Questions

Does SLT hurt?

Most patients have little to no pain. You may feel a slight tapping or ache during the laser, and mild aching afterward can last a few 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 does not cure glaucoma. Ongoing monitoring is essential because glaucoma can progress without symptoms.

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 appropriate patients, SLT can be a strong alternative to starting 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