SLT Laser

Selective Laser Trabeculoplasty, or SLT, is a form of laser surgery that is used to lower intraocular pressure in glaucoma.

It is used when eye drop medications are not lowering the eye pressure enough or are causing significant side effects. It can also be used as initial treatment in glaucoma. SLT has been in use for more than 25 years around the world.Selective laser trabeculoplasty (SLT) is an in-office procedure that reduces intraocular pressure in patients with glaucoma. The laser is applied through a special contact lens to the drainage system of the eye where it stimulates a biochemical change that improves the outflow of fluid from the eye.

SLT has been used since 1995 and has a proven track record for efficacy. On average, SLT can lower eye pressure by 20 to 30%. The laser is successful in about 80% of patients. In addition, studies have shown that SLT has a similar outcome compared to the most effective glaucoma eye drops. The treatment effect may last 3 to 5 years and SLT can be repeated when the original treatment effect diminishes.

Usually, eye drops are offered before laser for initial treatment of glaucoma. This stems from the era prior to SLT when laser trabeculoplasty was a relatively riskier procedure. Argon laser trabeculoplasty (ALT), the predecessor of SLT, delivered significantly higher laser energy to the eye resulting in structural damage and higher complication rates. By comparison, SLT has an improved safety profile where complications are typically infrequent, mild and short-lived. Although uncommon, side effects such as a “pressure spike” or inflammation can usually be successfully treated with a short course of medication.

Excellent Benefit-to-Risk Profile

Due to its excellent benefit-to-risk profile, SLT is being offered earlier in the treatment strategy of glaucoma, including as primary therapy. Studies comparing SLT and eye drops as primary therapy have found similar treatment effects between the two groups. Although some patients still required eye drops following SLT, they required fewer drops to control their glaucoma. In addition, there were significant cost savings for those getting SLT.

Many patients have difficulty with their eye drops. It is estimated that less than half of patients use their medications as regularly as directed. Medication costs, side effects, allergies, forgetfulness and complicated eye drop schedules contribute to this problem. As a result, there is a strong case for SLT as primary therapy for many new glaucoma patients. Glaucoma treatment is individualized for each patient, and SLT is not effective for all types of glaucoma. It is important to discuss your options with your eye care provider.


Who is a candidate for SLT?
Patients who have primary or secondary open-angle glaucoma (the drainage system in the front part of the eye is open) and are in need of lowering of their intraocular pressure (IOP) are eligible for the procedure. Your eye doctor will make the final determination if you are a candidate.

How does it work?
Laser energy is applied to the drainage tissue in the eye. This starts a chemical and biological change in the tissue that results in better drainage of fluid through the drain and out of the eye. This eventually results in lowering of IOP. It may take 1-3 months for the results to appear.

Why is it called Selective?
The type of laser used has minimal heat energy absorption because it is only taken up by selected pigmented tissue in the eye. Sometimes it is referred to as a “cold laser.” Because of this, the procedure produces less scar tissue and has minimal pain.

What are the risks?
One key aspect of SLT is a favorable side effect profile, even when compared with glaucoma medications. Post-operative inflammation is common but generally mild, and treated with observation or eye drops or an oral non-steroidal anti-inflammatory drug. There is an approximately 5% incidence of IOP elevation after laser, which can be managed by glaucoma medications and usually goes away after 24 hours.

How effective is it and how long does it last?
SLT lowers the IOP by about 30% when used as initial therapy. This is comparable to the IOP lowering of the most powerful and commonly used class of glaucoma medication (prostaglandin analogs). This effect may be reduced if the patient is already on glaucoma medications. The effect will generally last between 1-5 years, and in some cases, longer than that. If it does not last at least 6-12 months, it is usually not considered successful.

What happens if it wears off?
If SLT is effective at lowering IOP but this wears off over several years, the procedure can be repeated. Repeat treatments may or may not lower IOP as much as the first, and continued repeat laser will eventually not be effective. Some doctors may elect to treat half of the tissue on the first treatment, then treat the second half at a later date (this is not considered repeat treatment, and is completion of treatment). If SLT is not initially successful, repeat treatment is not likely to be effective. Alternatively, glaucoma medication can be used if the effect wears off over time.

What happens if it doesn’t work?
If SLT fails to lower the IOP, then the glaucoma is treated by other means such as medications or surgery. The laser does not affect the success of these other types of treatment.

What is the cost?
Since the procedure is an accepted glaucoma treatment, it is covered by most medical insurance. The cost for an uninsured individual or with an insurance co-pay will vary.

Will I still need to use glaucoma medications?
Some patients can be controlled with just laser treatment. Others require additional IOP lowering and may therefore need to use glaucoma medication as well. Think of the SLT as equivalent to one glaucoma medication. Just as some patients will require more than one glaucoma medication to control their IOP, some may also require laser plus one or more glaucoma medications. It is important to remember that SLT is not a cure for glaucoma, just as medication and surgery are not. Whatever method is used to treat glaucoma, appropriate follow up and testing with your eye care professional is critical.