Selective Laser Trabeculoplasty (SLT) is a non-invasive, outpatient procedure designed to manage high eye pressure, which is the primary risk factor for glaucoma. This laser treatment has become a widely accepted option for patients needing to reduce their intraocular pressure (IOP) to protect the optic nerve from damage. SLT is considered a gentle and repeatable therapy that enhances the eye’s natural fluid drainage system. It can be used alone as a first-line treatment or in combination with medicated eye drops to achieve the target pressure. The procedure is performed in a doctor’s office and takes only a few minutes.
How Selective Laser Trabeculoplasty Works
The underlying mechanism of glaucoma involves a buildup of fluid pressure inside the eye. This drainage system is a spongy tissue called the trabecular meshwork, which is located in the angle between the iris and the cornea. When this meshwork does not filter fluid effectively, the intraocular pressure rises, potentially damaging the optic nerve.
SLT employs short pulses of low-energy light directed at this trabecular meshwork. The “selective” nature of the treatment means the laser targets only the pigmented cells within the meshwork, leaving the surrounding tissue largely untouched. Unlike older laser treatments, SLT does not cause thermal damage or scarring to the drainage tissue.
Instead of creating physical openings, the absorbed laser energy stimulates a biological response. This response encourages the release of certain chemicals and attracts specialized white cells, which work to clean and remodel the meshwork. This cellular activity effectively increases the size of the pores in the drainage tissue, allowing the aqueous fluid to flow out of the eye more easily.
Patient Experience During the Procedure
The SLT procedure typically involves less than 10 minutes of actual laser application. Preparation begins with the administration of various eye drops, including an anesthetic to completely numb the eye surface. A drop to help prevent a temporary post-procedure pressure spike may also be given.
The patient is then seated at a slit lamp machine. A specialized contact lens is gently placed directly on the eye’s surface, which helps the doctor focus the laser beam precisely onto the trabecular meshwork. This lens also keeps the eye still and prevents blinking during the treatment.
During the application, the patient will likely see bright flashes of light and may hear a soft clicking sound with each laser pulse. Most patients report little to no pain, though mild tingling or pressure can occasionally be noticed. The doctor typically applies between 30 and 100 spots of laser energy around the drainage area.
Immediately following the laser application, the contact lens is removed, and the eye pressure is checked as a safety measure. The patient may experience temporary blurry vision, mild redness, or soreness in the treated eye. Patients are usually able to go home shortly after the pressure check and may be given a prescription for a temporary anti-inflammatory eye drop to use for a few days.
Expected Outcomes and Duration of Effect
The main goal of SLT is a sustained reduction in intraocular pressure (IOP), which is achieved in roughly 75% to 85% of treated patients. On average, the procedure can lower the eye pressure by 20% to 30%. The full pressure-lowering effect is not immediate and typically takes several weeks to fully manifest, with some patients noticing the maximum benefit after one to three months.
The duration of the pressure-lowering effect is variable among individuals, but it commonly lasts for one to five years. The treatment is often used to reduce or eliminate the need for daily medicated eye drops, though some patients may still require medication to reach their target pressure.
A significant advantage of SLT is the ability to be repeated if the pressure begins to rise again. Since the treatment does not cause permanent thermal damage or scarring, repeating the procedure is generally considered safe, though the success rate may be slightly lower with subsequent applications. Minor, temporary side effects are possible, most commonly including mild eye redness, irritation, or a temporary spike in eye pressure immediately following the treatment.