What Is Selective Laser Trabeculoplasty (SLT)?
Selective laser trabeculoplasty — commonly called SLT — is a laser procedure used to lower intraocular pressure in patients with open-angle glaucoma. The procedure targets the trabecular meshwork, the eye's natural drainage system, using short pulses of low-energy laser light to improve the outflow of aqueous humor (the clear fluid that fills the front of the eye). By enhancing drainage, SLT reduces intraocular pressure and helps protect the optic nerve from further damage.
SLT is one of the most commonly performed laser procedures for glaucoma worldwide. It is performed in the office in under 10 minutes, requires no incision, and has an excellent safety profile. At West Boca Eye Center in Boca Raton, Dr. Brent Bellotte uses SLT as both an alternative and a complement to glaucoma eye drops — and for many patients, SLT can significantly reduce or eliminate the need for daily drop medications.
How Does SLT Work?
The trabecular meshwork is a sponge-like tissue located at the base of the iris where it meets the cornea. In open-angle glaucoma, this tissue becomes less efficient at draining aqueous humor, causing fluid to accumulate and intraocular pressure to rise.
SLT uses a frequency-doubled Nd:YAG laser that selectively targets pigmented (melanin-containing) cells within the trabecular meshwork without damaging surrounding non-pigmented tissue. This selectivity is what distinguishes SLT from older laser trabeculoplasty techniques (such as ALT, or argon laser trabeculoplasty), which caused thermal damage to the tissue and could only be performed once or twice. Because SLT does not scar or structurally alter the trabecular meshwork, the procedure can be safely repeated if the pressure-lowering effect diminishes over time.
The exact biological mechanism by which SLT lowers pressure is still being studied, but it is believed to trigger a cellular response that remodels and rejuvenates the drainage tissue, restoring its ability to filter aqueous humor more effectively.
Who Is a Candidate for SLT?
SLT may be recommended for patients who:
- Have open-angle glaucoma or ocular hypertension (elevated eye pressure without optic nerve damage)
- Are not achieving adequate pressure control with eye drop medications alone
- Experience intolerable side effects from glaucoma eye drops (redness, stinging, fatigue, respiratory issues, depression)
- Have difficulty adhering to a daily drop schedule due to dexterity issues, forgetfulness, or cost
- Prefer a reduced medication burden as part of a dropless therapy approach
- Are newly diagnosed with open-angle glaucoma — SLT can be used as a first-line treatment before starting drops
SLT is not effective for all types of glaucoma. It is specifically designed for open-angle glaucoma and is not used to treat angle-closure glaucoma (which requires laser iridotomy) or secondary glaucoma caused by inflammation or trauma.
What to Expect During the Procedure
SLT is performed in the office at West Boca Eye Center and takes less than 10 minutes per eye. Here is what to expect:
- Before the procedure: Numbing eye drops are applied. You may also receive a drop to constrict the pupil (miotic drop) to improve access to the trabecular meshwork.
- During the procedure: A special mirrored contact lens (gonioscopy lens) is placed gently on the eye to allow the laser to reach the drainage angle. The laser delivers 50 to 100 short pulses of light to the trabecular meshwork. You may see brief flashes of green light and feel a mild snapping sensation, but the procedure is generally painless.
- After the procedure: The contact lens is removed and anti-inflammatory eye drops are applied. Your vision may be slightly blurred for a few hours. You can go home immediately but should arrange for someone to drive you.
Recovery and Results
SLT recovery is rapid compared to incisional glaucoma surgery:
- Day of treatment: Mild discomfort, light sensitivity, or blurred vision may occur. These typically resolve within a few hours. Anti-inflammatory drops are prescribed for 4 to 7 days.
- Week 1: Most patients resume all normal activities the day after treatment. There are no significant activity restrictions.
- Weeks 3–6: The full pressure-lowering effect develops gradually. Dr. Bellotte will check your intraocular pressure at follow-up visits during this period.
- Months 1–3: Pressure reduction is typically measurable within 1 to 3 months. The average IOP reduction with SLT is 20 to 30 percent, though results vary by patient.
The pressure-lowering effect of SLT typically lasts 1 to 5 years, with some patients maintaining benefit longer. If the effect diminishes, SLT can be repeated — unlike older laser procedures, SLT's non-destructive mechanism allows for retreatment.
SLT as First-Line Treatment
Traditionally, SLT was considered a second-line treatment — recommended only after eye drops failed to control pressure. However, clinical research has demonstrated that SLT is effective and safe as a first-line treatment for newly diagnosed open-angle glaucoma. The landmark LiGHT trial (Laser in Glaucoma and Ocular Hypertension Trial) found that initial SLT was at least as effective as eye drops at controlling intraocular pressure over 3 years, with the added benefit of eliminating the burden of daily medication for many patients.
Dr. Bellotte discusses SLT as a first-line option with appropriate candidates during their glaucoma evaluation at West Boca Eye Center.
SLT vs Other Glaucoma Treatments
- SLT vs eye drops: SLT achieves similar pressure reduction without the daily medication burden, side effects, or adherence challenges of eye drops. Many patients use SLT to reduce or eliminate their drop regimen.
- SLT vs ALT (argon laser trabeculoplasty): SLT is gentler on tissue and can be repeated, while ALT causes permanent scarring and is limited to one or two treatments.
- SLT vs trabeculectomy: SLT is far less invasive with fewer risks, but produces a more modest pressure reduction. Trabeculectomy is reserved for more advanced or uncontrolled glaucoma.
- SLT vs MIGS: Both are less invasive than traditional surgery, but SLT is performed in the office without incision, while MIGS requires an operating room and is typically combined with cataract surgery.
Risks and Side Effects
SLT has an excellent safety profile. Serious complications are rare. Possible side effects include:
- Temporary mild inflammation inside the eye (treated with anti-inflammatory drops)
- Temporary increase in intraocular pressure (typically resolves within 24 hours)
- Mild discomfort or aching in the treated eye for a few hours
- Light sensitivity for 1 to 2 days
- Rarely, the treatment may not produce a sufficient pressure reduction, requiring additional treatment
SLT does not cause the serious risks associated with incisional glaucoma surgery (infection, bleeding, hypotony, bleb complications). This favorable risk profile is one of the reasons SLT is increasingly used as a first-line treatment.
Schedule Your SLT Evaluation
Dr. Brent Bellotte at West Boca Eye Center provides comprehensive glaucoma evaluation and SLT treatment for patients with open-angle glaucoma and ocular hypertension. Whether you are newly diagnosed or currently managing glaucoma with eye drops, SLT may offer a path to better pressure control with less medication.
West Boca Eye Center is located at 9325 Glades Road, Suite 201, Boca Raton, FL 33434. Call (561) 488-1001 to schedule your glaucoma evaluation.
Frequently Asked Questions About SLT
Is SLT painful?
SLT is generally painless. The eye is numbed with anesthetic drops before the procedure. Some patients feel a mild snapping sensation or brief discomfort during treatment, but this is well tolerated. Any mild aching after the procedure typically resolves within a few hours.
How long does SLT last?
The pressure-lowering effect of SLT typically lasts 1 to 5 years, though some patients maintain benefit for longer. If the effect diminishes, the procedure can be safely repeated because SLT does not scar or permanently alter the trabecular meshwork.
Will I still need eye drops after SLT?
Some patients are able to reduce or discontinue their glaucoma eye drops after SLT, while others continue drops at a reduced dosage. The outcome depends on the severity of your glaucoma, your target intraocular pressure, and how your eye responds to treatment. Dr. Bellotte will adjust your medication plan based on your follow-up pressure measurements.
Can SLT be used as a first treatment for glaucoma?
Yes. Clinical research, including the LiGHT trial, has shown that SLT is effective and safe as a first-line treatment for newly diagnosed open-angle glaucoma. Many ophthalmologists now offer SLT as an initial treatment option before prescribing daily eye drops.
How many times can SLT be repeated?
SLT can be repeated if the pressure-lowering effect diminishes over time. Unlike older laser trabeculoplasty techniques (ALT), SLT does not cause scarring to the trabecular meshwork, which is why retreatment is possible. Most patients who undergo repeat SLT achieve similar results to their initial treatment.
