Selective Laser Trabeculoplasty, or SLT, is a form of laser surgery that is used to lower intraocular pressure in glaucoma.
It is used when eye drop medications are not lowering the eye pressure enough or are causing significant side effects. It may sometimes be used as initial treatment in glaucoma. SLT has been in use for 12 years in the United States and around the world.
Patients who have open-angle glaucoma (the drainage system in the front part of the eye is open) and are in need of lowering of their intraocular pressure (IOP) are eligible for the procedure.
Laser energy is applied to the drainage tissue in the eye. This starts a chemical and biological change in the tissue that results in better drainage of fluid through the drain and out of the eye. This eventually results in lowering of IOP. It may take 1-3 months for the results to appear.
There is minimal heat energy absorption because it is only taken up by selected pigmented tissue in the eye. Sometimes it is referred to as a “cold laser.” Because of this, the procedure produces less scar tissue and has minimal pain.
One key aspect of SLT is a favourable side effect profile, even when compared with glaucoma medications. Post-operative inflammation is common but generally mild, and treated with observation or eye drops or an oral non-steroidal anti-inflammatory drug. There is an approximately 5% incidence of IOP elevation after laser, which can be managed by glaucoma medications and usually goes away after 24 hours.
SLT lowers the IOP by about 30% when used as initial therapy. This is comparable to the IOP lowering of the most powerful and commonly used class of glaucoma medication (prostaglandin analogs). This effect may be reduced if the patient is already on glaucoma medications.
The effect will generally last between 1-5 years, and in rare cases, longer than that. If it does not last at least 6-12 months, it is usually not considered successful.
If SLT is effective at lowering IOP but this wears off over several years, the procedure can be repeated But the second treatment may not be as effective as the first and may not last as long. If SLT is not initially successful, repeat treatment is not likely to be effective. Alternatively, glaucoma medication can be used if the effect wears off over time.
If SLT fails to lower the IOP, then the glaucoma is treated by other means such as medications or conventional surgery. The laser does not affect the success of these other types of treatment.
Since the procedure is an accepted glaucoma treatment, it is covered by Medicare and medical insurance.
Some patients can be controlled with just laser treatment. Others require additional IOP lowering and may therefore need to use glaucoma medication as well. Think of the SLT as equivalent to one glaucoma medication. Just as some patients will require more than one glaucoma medication to control their IOP, some may also require laser plus one or more glaucoma medications. It is important to remember that SLT is not a cure for glaucoma, just as medication and aggressive surgeries are not.