Intraocular pressure (IOP), or pressure inside the eye, must be managed to prevent progressive and irreversible vision loss associated with glaucoma. Selective Laser Trabeculoplasty, or SLT, is a common, non-invasive treatment option used to control this pressure. This laser procedure improves the eye’s natural fluid drainage system, serving as an alternative or supplement to daily eye drop medications.
Understanding Selective Laser Trabeculoplasty
The primary goal of SLT is to lower the intraocular pressure by targeting the trabecular meshwork, a tissue structure responsible for filtering fluid out of the eye. This treatment is predominantly used for Primary Open-Angle Glaucoma (POAG), the most widespread form of the condition. In POAG, the drainage angle is open, but the meshwork itself is not functioning efficiently, leading to a buildup of aqueous humor fluid.
SLT is a modern evolution of earlier laser procedures, such as Argon Laser Trabeculoplasty (ALT), but its “selective” nature marks a significant difference. While both aim to improve outflow, SLT uses a gentler approach that avoids causing permanent damage or scarring to the eye’s drainage tissue. The treatment effectively addresses the underlying resistance to fluid outflow, which is the cause of elevated IOP in open-angle glaucoma.
The Specific Mechanism of the Laser
The scientific principle behind SLT relies on a specialized, low-energy laser that targets specific cells within the trabecular meshwork. This laser uses short pulses of light, which are absorbed only by the pigmented cells containing melanin, leaving the surrounding non-pigmented tissue untouched.
Instead of causing a destructive effect, the absorbed energy creates a biological, cellular response within the treated tissue. This triggers the release of certain chemical messengers, which stimulate the body’s natural healing mechanisms. Macrophages are recruited to the area, aiding in the remodeling of the meshwork’s extracellular matrix. This process effectively increases the number and size of the pores, thus enhancing the outflow facility of the aqueous humor and lowering the intraocular pressure.
What to Expect During the Procedure
The Selective Laser Trabeculoplasty procedure is performed in an outpatient setting, typically in the ophthalmologist’s office. You should expect the entire appointment to take a few hours due to necessary preparation and post-procedure observation, although the laser application itself is very quick. Preparation involves administering several types of eye drops, including a topical anesthetic to numb the eye’s surface and sometimes a drop to help prevent a temporary pressure spike.
During the procedure, you will be seated at a machine similar to the one used for routine eye exams, known as a slit lamp. The doctor will place a special mirrored contact lens directly onto the eye to focus the laser light onto the trabecular meshwork. The laser pulses are often described as a soft clicking sound, and you may see bright flashes of light. The application of the laser usually takes only five to ten minutes per eye.
Immediately after the treatment, an anti-inflammatory drop is typically instilled, and the contact lens is removed. Your vision may be temporarily blurry and sensitive to light, and it is strongly advised not to drive yourself home after the procedure. A technician will recheck your intraocular pressure approximately 30 to 60 minutes after the treatment to ensure stability before you are released.
Efficacy and Post-Procedure Life
SLT is an effective option for lowering intraocular pressure, often achieving a reduction in the range of 25 to 30% from the baseline pressure. The full pressure-lowering effect is not immediate and generally takes several weeks, often up to six, to become fully apparent. For many patients, this reduction can allow them to use fewer glaucoma medications or, in some cases, remain medication-free for a period.
The longevity of the pressure-lowering effect varies, but most eyes remain controlled for an average of three to five years after a single treatment. Expected temporary side effects can include mild irritation, soreness, or a transient spike in intraocular pressure immediately following the laser application. Follow-up appointments are scheduled to monitor the pressure and confirm the success of the treatment over time.