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What Is Laser Trabeculoplasty (ALT/SLT)?

Laser trabeculoplasty is a glaucoma laser treatment that targets the trabecular meshwork to improve fluid outflow and lower intraocular pressure. Argon laser trabeculoplasty (ALT) uses a thermal laser effect, while selective laser trabeculoplasty (SLT) uses lower-energy pulses that target pigmented cells more selectively. Both are commonly used for open-angle glaucoma or ocular hypertension. The pressure-lowering effect can be significant but may lessen over time, and follow-up is essential.

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What Is Laser Trabeculoplasty (ALT/SLT)?

Laser trabeculoplasty is a glaucoma laser treatment that targets the trabecular meshwork to improve fluid outflow and lower intraocular pressure. Argon laser trabeculoplasty (ALT) uses a thermal laser effect, while selective laser trabeculoplasty (SLT) uses lower-energy pulses that target pigmented cells more selectively. Both are commonly used for open-angle glaucoma or ocular hypertension. The pressure-lowering effect can be significant but may lessen over time, and follow-up is essential.

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ALT vs SLT

ALT and SLT aim for the same outcome, improved aqueous outflow through the trabecular meshwork, but they differ in how energy is delivered. ALT uses an argon laser that creates small thermal burns, while SLT uses a frequency-doubled Nd:YAG laser with selective targeting and less structural damage. SLT is often considered more repeatable than ALT, though repeat outcomes can vary. Your doctor chooses the approach based on glaucoma type, prior treatments, and eye anatomy.

Who It Helps and When It's Used

Laser trabeculoplasty is most often used for primary open-angle glaucoma and ocular hypertension. It may be used as an initial therapy, a way to reduce reliance on drops, or an add-on when medications are not enough. It is not a cure, but it can help slow glaucoma progression by lowering pressure. Some glaucoma subtypes respond less, so diagnosis and angle assessment matter.

What to Expect During and After Treatment

  1. Numbing drops are placed, and a special contact lens is used to view the trabecular meshwork.
  2. The laser is applied around part or all of the drainage angle, typically in minutes.
  3. Eye pressure is checked after, and anti-inflammatory drops may be prescribed.

Vision may be mildly blurry for a short time, and you will have follow-up visits to confirm pressure response.

Risks and Follow Up

Common short-term effects include inflammation, mild discomfort, and a temporary pressure spike, which is why monitoring after treatment is important. The pressure-lowering effect may wear off, and some patients need repeat laser or other therapy. Serious complications are uncommon, but any severe pain, marked redness, or sudden vision change should be evaluated promptly. Continue prescribed glaucoma drops unless your doctor instructs otherwise.

FAQs on Laser Trabeculoplasty (ALT/SLT)

How long does SLT or ALT last?

Many patients get months to years of pressure lowering, but duration varies. Effectiveness can decline over time as glaucoma progresses or the eye's response changes. Your doctor will monitor pressure and optic nerve health to decide if additional treatment is needed.

Can SLT replace glaucoma eye drops?

In some people, yes, at least temporarily, but not always. SLT can be used as first-line therapy or as an add-on, and some patients can reduce the number of drops. Others still need drops to reach target pressure.

Is laser trabeculoplasty safe to repeat?

SLT is commonly repeated in selected patients, though repeat response can be smaller than the initial effect. ALT is generally less repeatable because of its thermal effects on tissue. Your doctor will base repeat decisions on angle health, prior response, and glaucoma control needs.

What symptoms after treatment should worry me?

Contact your clinic urgently if you have severe pain, nausea, marked redness, sudden vision loss, or rapidly worsening blur. Mild irritation and temporary blur can be normal, but symptoms should improve over time. Your doctor may also instruct you to come in if pressure feels high or headaches occur.

References

Laser Trabeculoplasty. EyeWiki. https://eyewiki.org/Laser_Trabeculoplasty. Date Accessed February 9, 2026.

Laser Trabeculoplasty. StatPearls (NCBI Bookshelf, National Institutes of Health). https://www.ncbi.nlm.nih.gov/books/NBK557534/. Date Accessed February 9, 2026.

Primary Open-Angle Glaucoma Preferred Practice Pattern®. American Academy of Ophthalmology. https://www.aao.org/Assets/1d611244-4cd3-4f61-af0c-338c4b5cafb3/637355417046100000/primary-open-angle-glaucoma-ppp-pdf. Date Accessed February 9, 2026.

Laser in Glaucoma and Ocular Hypertension (LiGHT) Trial. Ophthalmology. https://www.aaojournal.org/article/S0161-6420(23)00070-7/fulltext. Date Accessed February 9, 2026.

Selective Laser Trabeculoplasty: An Updated Narrative Review. PubMed Central (National Library of Medicine). https://pmc.ncbi.nlm.nih.gov/articles/PMC11369595/. Date Accessed February 9, 2026.