Selective Laser Trabeculoplasty (SLT) - Glaucoma Laser Eye Surgery

Selective Laser Trabeculoplasty is an Alternative to Medicine for Treating Glaucoma

Selective Laser Trabeculoplasty (SLT) is a  type of laser eye surgery used to decrease intraocular pressure (IOP) in open-angle glaucoma patients. This is achieved by increasing the drainage of aqueous fluid from the eye through the trabecular meshwork.  After SLT, the IOP drops quickly the first day and stabilizes over the first two months.  SLTs are usually performed in cases where glaucoma and IOP are unable to be controlled with glaucoma medical eye drops;  however, this procedure can be performed at anytime during the management of glaucoma.  Recent studies have suggested that SLT is the same, if not better, than current eye drop medications as a first line treatment and SLT is gaining popularity as a first line treatment instead of or in addition to medicine eye drops.

SLT is similar to ALT (argon laser trabeculoplasty), but is a newer, more selective procedure and uses shorter laser pulses.  SLT only targets cells in the trabecular meshwork that contain melanin, while ALT targets all cells in the trabecular meshwork.  This allows SLT to result in less damage and less scarring of the surrounding tissue than ALT.  This is a significant difference because the damage caused by ALT may prevent use of some newer types of glaucoma procedures such as iStent or the Hydrus (not yet approved in the U.S.).

Steps of the SLT Procedure

SLT is an in-office procedure.  Prior to the surgery, anesthetic eye drops will be instilled on the eye. The procedure is performed at the slit lamp (microscope) while the doctor holds a special type of lens against the eye. The patient may see light flashes and hear a beeping sound during the laser surgery. Prescription eye drops will be applied after the SLT procedure to help reduce inflammation and/or infection. The patient may experience mild ocular irritation and discomfort following SLT.  

The laser used in SLT targets only pigmented cells in the trabecular meshwork of the eye.  There is virtually no effect or damage to surrounding tissue.  The laser pulse is so short that any heat generated does not transfer to nearby tissue.  ALT however does cause damage to surrounding tissue.  The wavelength of light generated by SLT targets the melanin of the pigmented cells and stimulates the eye’s natural mechanism to increase aqueous outflow out of the eye and lower intraocular pressure.

Multiple follow up visits will be required in order to monitor IOP and the success of the procedure. Follow up visits typically occur 1 day, 2 weeks, and 2 months after SLT is performed. If both eyes require treatment, the procedure will be performed on two separate visits. Multiple treatments may also be required. In some cases, IOP lowering eye drops may still be needed after SLT is performed in order to control glaucoma. Most patients can stop at least one of their eye drop medicines.

Side effects after SLT can include inflammation, bleeding, change in glasses prescription and increase in IOP.  These side effects are rare and can be managed effectively.  

Patient Selection for Selective Laser Trabeculoplasty

SLT can only be performed on patients with open-angle forms of glaucoma.  This is a successful option for both first line treatment and adjunct therapy with topical medications. 

This procedure is beneficial in patients who are concerned about the cost of medications, side effects associated with medications, and/or those who have difficulty using eye drops.      

SLT patients are still eligible to have iStent surgery in the future.  ALT patients often do not benefit from iStent due to fibrosis and scarring and destruction of many cells in the trabecular meshwork.

SLT is covered by Medicare and virtually all medical insurance companies.  Even without insurance the procedure is very affordable.

Prognosis after SLT

SLT results in a decreased intraocular pressure similar to an amount achieved by the typical first line medicine used by most eye doctors.  Unfortunately, most people will still need to use some eye drop medicine even after having the SLT procedure.

SLT can be performed multiple times on the same eye.  This is important because the effects of SLT diminish after a few years and it becomes necessary to perform the procedure again and again over the course of 7-8 years.  Unfortunately, SLT is not a one and done procedure.  It will have to be repeated several times over the years and ultimately the benefits of IOP lowering will be reduced and further SLT will not be used at some point due to its diminished results.

An advantage of SLT vs. medical treatment is that there is no possibility of patient non-compliance or forgetting to use the eye drops.  SLT also works constantly 24 hours per day with no high and low pressure periods that often occurs with eye drop medicine.  There are also no systemic side effects or ocular side effects with SLT like there is with medicine.