Selective Laser Trabeculoplasty (SLT) is a medical procedure used to reduce intraocular pressure (IOP) in individuals with primary open angle glaucoma. It is a type of laser surgery that targets the drainage system of the eye, specifically the trabecular meshwork, to improve fluid outflow and lower the IOP. Here’s how SLT works:

  1. Preparation: The patient is typically given topical anesthetic eye drops to numb the eye and prevent discomfort during the procedure.
  2. Laser application: Using a specialized laser and a specialized lens on the surface of the cornea, the ophthalmologist delivers short pulses of low-energy light to the trabecular meshwork, which is located near the angle where the cornea and iris meet. The laser used in SLT is typically a Q-switched, frequency-doubled, Nd:YAG laser.
  3. Selective targeting: SLT utilizes a specific wavelength of light (usually 532 nm) that is selectively absorbed by melanin-containing cells within the trabecular meshwork. Melanin is a pigment naturally present in the eye’s drainage structures. The laser energy is primarily absorbed by these melanin-containing cells while sparing the surrounding tissue.
  4. Cellular response: When the laser energy is absorbed by the targeted cells, it stimulates a biochemical response within the meshwork. This triggers the release of cytokines and other signaling molecules that initiate a series of cellular and molecular events.
  5. Inflammatory process: The cellular response leads to a mild, localized inflammation in the trabecular meshwork. This inflammation causes structural changes in the tissue and enhances the function of the drainage channels, improving the outflow of aqueous humor from the eye.
  6. Improved drainage and reduced IOP: As the inflammation resolves, the remodeling of the trabecular meshwork results in increased flow capacity through the drainage system. This helps to lower the IOP by improving the eye’s ability to regulate fluid outflow.

It is important to note that the exact mechanism by which SLT reduces eye pressure is not fully understood. However, it is believed that SLT acts through a combination of cellular and tissue changes within the trabecular meshwork, leading to improved aqueous humor drainage.

SLT is generally considered a safe and effective procedure for lowering IOP in individuals with glaucoma. However, it may not be suitable for all patients, and the decision to undergo SLT should be made in consultation with your ophthalmologist or glaucoma specialist.

How effective is SLT?

  1. Studies have reported that SLT can lead to an average IOP reduction of around 20-30%, although individual responses can vary. The IOP-lowering effect of SLT is typically seen within a few weeks after the procedure.
  2. Long-term efficacy: SLT has demonstrated good long-term efficacy in maintaining IOP reduction. Studies have indicated that the IOP-lowering effect of SLT can last for several years. However, the duration of the effect may vary among individuals, and periodic follow-up visits are essential to monitor the IOP and adjust the treatment plan if needed.
  3. Repeatability: SLT can be repeated if necessary. If the initial SLT procedure does not achieve the desired IOP reduction or if the effect diminishes over time, a repeat SLT treatment may be considered. Repeating SLT has been shown to provide additional IOP reduction in some cases.
  4. Medication reduction: SLT may allow for a reduction in the use of glaucoma medications. Some patients may be able to decrease their reliance on topical medications or require fewer medications after undergoing SLT. However, the need for medication reduction will be evaluated on an individual basis, and it is important to work closely with your ophthalmologist to determine the appropriate treatment plan.

It’s worth noting that while SLT can effectively lower IOP in many cases, it may not eliminate the need for ongoing glaucoma management. Regular follow-up visits, ongoing monitoring, and potential adjustments to the treatment plan are still necessary to maintain optimal eye health and manage glaucoma effectively.

As with any medical procedure, the effectiveness of SLT can vary depending on individual factors.

Surgeon Tips: When undergoing SLT laser, expect to hear a small noise from the laser and see a small flashes of light like a flash on a camera.  A typical procedure takes five or so minutes to complete.  Most surgeons will aim to place 80-100 pulses 360 degrees around the trabecular meshwork. There is almost no discomfort during the procedure.  Some patients describe feeling a “tingle” in the eye when the laser light is applied. 

The vision will probably be blurred for a few hours after the procedure due to the gel that is placed on the surface of the eye which allows the specialized SLT lens to be placed comfortably on the surface of the cornea. A drop will be given after the laser treatment to prevent a rise in pressure in the eye.  There are no restrictions on your activities after the procedure.

If you are on drops for glaucoma, you should continue taking them in the same way after the procedure.  The doctor will notify you if there is any exception to continuing your medications. 

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