Laser trabeculoplasty is a common, non-invasive outpatient treatment used to manage open-angle glaucoma. The procedure uses a specialized low-energy laser to target the eye’s internal drainage system. Its primary purpose is to reduce the fluid pressure inside the eye. This helps preserve the patient’s vision and slows the progression of the disease.
The Target: Understanding Intraocular Pressure and Glaucoma
Glaucoma is a group of eye diseases characterized by progressive damage to the optic nerve, which transmits visual information to the brain. This damage is most often linked to consistently elevated intraocular pressure (IOP). The pressure build-up occurs because the eye’s natural fluid, known as aqueous humor, cannot drain properly.
Aqueous humor is produced constantly and must exit the eye at an equal rate to maintain stable pressure. Drainage occurs primarily through the trabecular meshwork, a microscopic, sponge-like structure located where the iris meets the cornea. In open-angle glaucoma, the meshwork becomes clogged or inefficient, creating resistance to fluid outflow. Laser trabeculoplasty targets this structure to restore its function and improve the flow of aqueous humor.
Mechanism of Action: How the Laser Opens Drainage
The laser energy applied during the procedure does not burn or drill holes into the trabecular meshwork tissue. Instead, the laser initiates a biological and cellular response within the drainage angle. The energy is absorbed by the pigmented cells in the meshwork, stimulating a healing reaction.
This stimulation causes the release of chemical mediators and enzymes that actively remodel the extracellular matrix within the meshwork tissue. This cellular activity leads to the clearing of debris and an increase in the tissue’s permeability.
The biological remodeling process physically opens the microscopic channels of the trabecular meshwork. The laser also appears to increase the conductivity of the cells lining Schlemm’s canal, the main collector channel for the aqueous humor. This combined effect facilitates better fluid outflow, which ultimately lowers the intraocular pressure.
Comparing SLT and ALT Techniques
There are two primary types of laser trabeculoplasty, each utilizing a different laser technology to achieve the same pressure-lowering effect. Argon Laser Trabeculoplasty (ALT) was the original technique, employing a continuous-wave argon laser. The ALT laser energy is absorbed by the pigmented cells, creating localized thermal damage that results in small, microscopic coagulation burns or scars on the trabecular meshwork tissue.
Selective Laser Trabeculoplasty (SLT) is a newer method. The key difference is that SLT uses very short, low-energy pulses that are absorbed selectively by the pigmented cells without causing widespread thermal damage to the surrounding tissue. This non-destructive approach causes far less scarring in the drainage angle compared to ALT.
The lower level of tissue damage with SLT is why it is considered potentially repeatable, whereas ALT is generally a one-time treatment for a given area. Despite their different mechanisms of action, clinical studies have shown that both SLT and ALT demonstrate a similar level of efficacy in reducing intraocular pressure over the long term. SLT has become the more common technique due to its gentler nature and repeatability.
The Patient Experience and Post-Procedure Care
Laser trabeculoplasty is performed in an outpatient setting and typically takes only five to ten minutes per eye. Before the procedure begins, the eye is numbed with anesthetic drops, and sometimes a pressure-lowering drop is administered to prevent a temporary pressure spike. The patient sits at a specialized laser machine, which looks similar to the slit lamp microscope used for a standard eye exam.
A special contact lens is placed gently on the eye’s surface, allowing the doctor to visualize the trabecular meshwork and focus the laser energy. The patient may hear a clicking sound and see a flash of green light with each pulse, but the procedure is generally painless. There may be a sensation of mild pressure while the lens is on the eye.
Following the procedure, patients often wait up to an hour so the eye pressure can be checked for spikes. Patients are prescribed anti-inflammatory eye drops to use for several days to minimize temporary irritation or inflammation. Mild redness, light sensitivity, or slight blurring of vision are common, temporary side effects that usually resolve within a day.
The full pressure-lowering effect is not immediate, as it depends on the biological remodeling process. While some pressure reduction may be noted within a few weeks, the maximum benefit usually takes between one and three months to fully develop. Patients must continue using their regular glaucoma medication until the full effect of the laser is assessed at a follow-up appointment.