Selective Laser Trabeculoplasty (SLT) is a non-invasive, outpatient laser treatment used to manage open-angle glaucoma. The procedure lowers the intraocular pressure (IOP) within the eye. Elevated IOP is the primary risk factor for glaucoma, causing progressive damage to the optic nerve. Controlling this pressure is necessary to prevent irreversible vision loss.
Understanding the SLT Procedure
The SLT procedure focuses a low-energy laser beam onto the eye’s natural drainage system, known as the trabecular meshwork. This meshwork is a spongy tissue located where the iris and cornea meet. The laser energy is applied in short pulses, targeting specific pigmented cells within the drainage tissue.
This selective targeting initiates a biological change within the meshwork cells. The stimulation triggers a natural healing response, restructuring the tissue and improving the outflow of aqueous humor from the eye. SLT is non-thermal, meaning it does not cause thermal damage or scarring to the surrounding tissue. This gentler approach allows the procedure to be safely repeated if the effect wears off over time.
The Expected Timeframe of Effectiveness
The primary goal of SLT is to achieve a significant and sustained reduction in intraocular pressure (IOP). On average, the procedure lowers IOP by about 20% to 30% in responding patients. While some patients may notice an effect within days, the full pressure-lowering benefit often takes one to two months to fully manifest.
The duration of this IOP reduction is variable, but the therapeutic effect typically lasts between one and five years. Specific data suggests the average benefit persists for approximately three to four years.
Roughly half of all treated eyes maintain their pressure reduction five years after the initial procedure. Success is measured by achieving a predefined target pressure or a specific percentage reduction from the baseline IOP. The pressure control tends to wane gradually over time, necessitating continued monitoring by an eye care professional.
Why Treatment Duration Varies
Several patient and disease characteristics influence how long the pressure-lowering effect of SLT lasts.
One of the strongest predictors of a robust response is the patient’s intraocular pressure before the procedure. Patients starting with a higher baseline IOP often experience a greater percentage reduction in pressure and a longer duration of effect.
The type and severity of glaucoma also play a role, with some forms, such as pseudoexfoliative glaucoma, showing a higher initial success rate. The patient’s current medication regimen can affect the outcome. Individuals who are not yet using glaucoma eye drops or are on fewer medications often see a more pronounced and durable pressure reduction.
Younger patients, particularly those under the age of 60, have also been observed to have a better overall response and greater IOP decrease. Other factors, such as the presence of diabetes, may be associated with a shorter duration of the pressure-lowering effect. The extent of the treatment, such as treating the entire 360 degrees of the trabecular meshwork, may also contribute to better long-term outcomes.
Options After Pressure Returns
The effect of SLT is not permanent, and intraocular pressure will eventually begin to rise again in most patients. When this occurs, the first consideration for maintaining eye health and controlling pressure is re-treatment with SLT.
Because the procedure does not cause scarring, repeating the SLT treatment is generally considered safe. A second SLT can sometimes be as effective as the first, potentially achieving a longer duration of pressure control. However, the success rate of subsequent treatments may decrease with each repetition, and not all eyes that initially responded will respond a second time.
If repeat laser treatment is unsuccessful or not indicated, the treatment plan typically reverts to or increases the use of glaucoma eye drop medications. If medical and laser therapy are insufficient to reach the target pressure, the next steps involve surgical intervention. These options include conventional filtering procedures, such as trabeculectomy, or newer techniques like Minimally Invasive Glaucoma Surgery (MIGS).