Selective Laser Trabeculoplasty (SLT) is a common, non-invasive laser procedure used in ophthalmology to manage intraocular pressure (IOP), the primary treatment target for open-angle glaucoma. SLT uses a low-energy laser to treat the eye’s natural drainage system, reducing fluid pressure inside the eye. It is often utilized as a first-line therapy or in conjunction with medication for patients with ocular hypertension or various forms of open-angle glaucoma. This treatment offers a way to lower eye pressure without daily eye drops, making it a valuable option for long-term care.
Understanding the Selective Mechanism
The “selective” aspect refers to the laser’s ability to target specific pigmented cells within the eye’s drainage tissue, known as the trabecular meshwork. This highly specific targeting is achieved through selective photothermolysis, using a frequency-doubled, Q-switched Nd:YAG laser with a very short pulse duration, typically three nanoseconds.
The absorbed light energy increases the temperature only within the pigmented cells, avoiding significant heat damage or scarring to the surrounding non-pigmented tissue. This differs from older laser procedures, which caused coagulative damage and limited retreatment. The gentle energy delivery stimulates a biological response, encouraging natural healing mechanisms to clean and remodel the trabecular meshwork.
This stimulated cellular response improves the outflow of aqueous humor, the fluid responsible for eye pressure, through the drainage angle. While the exact mechanism is not completely understood, it involves the release of biological mediators that help increase the porosity and function of the meshwork. This process leads to a sustained reduction in resistance to fluid outflow, lowering the intraocular pressure.
The low-energy, non-thermal nature of the treatment makes the procedure repeatable for long-term pressure management. Since the laser avoids structural damage, the drainage tissue remains intact, unlike previous treatments that created scar tissue. The goal is to enhance the function of the natural drain, preserving the option for future treatment if pressure rises again.
The Patient Experience During the Procedure
The SLT procedure is performed in a doctor’s office or clinic setting, typically requiring the patient to be present for about two hours. The eye is prepared using topical anesthetic drops to numb the surface. A special contact lens is then placed on the eye to help the ophthalmologist focus the laser beam precisely onto the trabecular meshwork.
The patient is seated at a machine similar to a slit lamp microscope. During the laser application, the patient may see bright flashes of light and hear a clicking sound. The procedure is generally painless, though some patients report a mild tingling sensation or slight pressure in the eye.
The actual laser treatment is brief, often taking only three to ten minutes per eye. If both eyes require treatment, they may be done on the same day or scheduled separately. Afterward, the contact lens is removed, and the doctor may administer anti-inflammatory drops or drops to prevent a temporary rise in eye pressure.
Recovery and Long-Term Outcomes
Immediately after the procedure, vision may be temporarily blurry, and the eye might feel slightly scratchy or sensitive to light for a few hours. Patients are advised not to drive themselves home. The ophthalmologist often checks the eye pressure about an hour after treatment to monitor for any immediate pressure spikes.
Patients are typically prescribed anti-inflammatory eye drops for a few days to manage minor post-procedure inflammation or discomfort. There are generally no restrictions on returning to normal daily activities by the next day. The full pressure-lowering effect is gradual, unfolding over several weeks to months.
A reduction in intraocular pressure usually begins within one to three months. SLT successfully lowers eye pressure by an average of 20 to 30 percent in approximately 75 to 80 percent of patients. While the duration varies widely, the benefit typically lasts between one and five years.
SLT is repeatable, allowing for subsequent treatments if eye pressure begins to climb again. Since the treatment does not cause irreversible scarring, it does not preclude the use of other glaucoma treatments, such as medications or incisional surgery, in the future. Follow-up appointments are scheduled six to eight weeks after the procedure to assess the final outcome and adjust any ongoing medication regimen.
Potential Side Effects and Patient Candidacy
SLT is considered a safe procedure with a low risk of serious complications, though patients may experience temporary side effects. The most common include mild eye redness, light sensitivity, and temporary inflammation (iritis) in the days following the laser. These effects are generally mild, resolve on their own, and are often managed with prescribed anti-inflammatory eye drops.
A temporary spike in intraocular pressure immediately following the procedure is a known risk in a small percentage of patients. Doctors often administer drops before or after the procedure to prevent or manage this potential spike, which is usually short-lived and controlled with medication. Rare, more serious complications, such as prolonged inflammation or corneal issues, have been reported but are uncommon.
SLT is a treatment option for patients with various forms of open-angle glaucoma and ocular hypertension. Conditions treated include:
- Primary open-angle glaucoma
- Pigmentary glaucoma
- Pseudoexfoliation glaucoma
- Ocular hypertension
It is particularly useful for individuals who have difficulty adhering to a daily eye drop schedule or who experience side effects from glaucoma medications. SLT can be used as a first-line treatment or as an add-on therapy when pressure is not adequately controlled with medication alone.
Patients with inflammatory types of glaucoma or heavily pigmented drainage angles may carry an increased risk of a post-laser pressure spike and require careful consideration. The treatment is not suitable for patients with angle-closure glaucoma or those with narrow anterior chamber structures. The decision to proceed with SLT is based on the type of glaucoma, the current level of eye pressure, and the patient’s overall health and treatment goals.