Glaucoma is a condition where pressure builds up inside the eye, often referred to as intraocular pressure (IOP), which can lead to damage of the optic nerve. If left untreated, this pressure can progressively injure the nerve responsible for transmitting visual information to the brain, potentially causing irreversible vision loss. Selective Laser Trabeculoplasty (SLT) is a non-invasive, outpatient laser treatment designed to safely lower elevated IOP. The procedure uses a specific laser to improve the eye’s natural fluid drainage system.
How SLT Differs from Other Glaucoma Treatments
SLT presents an alternative to traditional glaucoma management, which often begins with prescription eye drops. While drops are effective, they require strict adherence to a daily schedule and can cause side effects like eye irritation, redness, or changes in eyelash growth. For many patients, the daily challenge of using drops is a major hurdle to consistent pressure control.
The SLT procedure also differs significantly from older laser treatments, such as Argon Laser Trabeculoplasty (ALT). ALT uses a continuous beam to create small, permanent burn scars in the drainage tissue, which improves fluid outflow but causes thermal damage. Because of this destructive nature, ALT can typically only be performed once per eye. In contrast, SLT is non-destructive and can be repeated if the pressure-lowering effect wears off, offering an advantage in long-term management.
The Mechanism of Selective Laser Trabeculoplasty
The science behind SLT is based on “selective photothermolysis,” which allows the laser to target specific cells without harming surrounding tissue. The treatment uses a low-energy, frequency-doubled Nd:YAG laser that emits extremely short bursts of light. This specific wavelength and short pulse duration mean the energy is only absorbed by the pigmented cells within the trabecular meshwork, the eye’s natural drainage filter.
The pigmented cells absorb the laser energy, causing a localized reaction without creating thermal damage or scarring in the non-pigmented tissue nearby. This precise targeting stimulates a biological response that encourages the body’s immune cells to clean up and remodel the drainage system. The resulting cellular changes effectively widen the pores of the meshwork, increasing the outflow of aqueous humor, which safely reduces the pressure inside the eye.
What to Expect During the Procedure
The SLT procedure is performed in an outpatient setting and is generally quick, often taking only five to ten minutes for each eye. Before the treatment begins, the doctor administers numbing drops to the eye, ensuring the procedure is painless. A special contact lens is then placed on the eye’s surface to help focus the laser beam onto the drainage angle.
During the session, the patient is seated comfortably at a machine similar to the slit lamp microscope used for routine eye exams. The patient may hear a clicking sound and see bright flashes of light as the laser is applied. While the procedure is usually pain-free, some individuals report a mild sensation of pressure or slight prickling. Once the treatment is complete, the contact lens is removed, and the patient is ready for release shortly after.
Recovery and Long-Term Expectations
Following the procedure, patients are often prescribed anti-inflammatory eye drops for a short period to manage mild swelling or irritation. It is common to experience temporary side effects such as slight eye redness, blurred vision, or increased light sensitivity for a few hours or days. Patients can typically resume most normal activities, including driving, the day after the procedure, but they should avoid strenuous activity for the first 24 hours.
The pressure-lowering effect of SLT is not immediate and usually takes days to several weeks to fully manifest. Most patients experience an IOP reduction of about 20 to 30 percent. The duration of effectiveness varies among individuals but often lasts between one and five years. Since SLT does not cause permanent tissue damage, it can be safely repeated if the pressure begins to rise again, offering a sustainable option for managing glaucoma.