Selective Laser Trabeculoplasty (SLT) and Glaucoma
Glaucoma is a progressive neuropathy that affects the optic nerve, Cranial Nerve II, the cable that connects the eyes to the brain. If left untreated or undiagnosed for a period of time, glaucoma can lead to blindness.
Reducing intraocular pressure (IOP) (the pressure of your eyeball, like the pressure of your tire) seems to be the only treatment proven to slow progression in glaucoma.1
There are many methods to reduce IOP: pharmaceutical treatment, laser treatment, and surgery.
Argon laser trabeculoplasty (ALT) was introduced about 35 years ago and involves the use of a blue/green argon laser (major wavelength peaks at 488 nm and 514 nm) to treat the outer part of the trabecular meshwork and thereby improve aqueous flow and thus reduce IOP.
Selective Laser Trabeculoplasty (SLT) uses a 532-nm frequency-doubled, Q-switched Nd:YAG laser that delivers a low-energy, large spot, very brief pulse to selectively target cells of the trabecular meshwork. This “milder” laser application is thought to stimulate the pigmented trabecular meshwork cells and thus facilitate improved aqueous outflow. The exact mechanism of action for reducing the IOP is not fully understood.
In the Glaucoma Laser Trial Follow-up Study, after 7 years of follow-up, patients who had undergone argon laser trabeculoplasty (ALT) had lower IOP than patients on pharmaceutical treatment.2,3
However, there has been no randomized trial comparing SLT to medical treatment. SLT appears to be less costly than current medical treatment.4 Daily drops cost patients millions of dollars every years. Many of these drops have significant systemic side effects that lead to lack of compliance (drops are not used or skipped), and thus poor eye pressure control.
SLT is effective and can be repeated if needed. This allows patients to decrease the number of drops and the frequency of use.
References: above adapted from: Clin Ophthalmol. 2011; 5: 1469–1473. Comparison of selective laser trabeculoplasty (SLT) in primary open angle glaucoma and pseudoexfoliation glaucoma Marcelo Ayala and Enping Chen
1. Leske MC, Heijl A, Hussein M, Bengtsson B, Hyman L, Komaroff E. Early Manifest Glaucoma Trial Group. Factors for glaucoma progression and the effect of treatment: the early manifest glaucoma trial.Arch Ophthalmol. 2003;121(1):48–56. [PubMed]
2. The Glaucoma Laser Trial Research Group. The Glaucoma Laser Trial (GLT). Results of argon laser trabeculoplasty versus topical medicines. Ophthalmology. 1990;97(11):1403–1413. [PubMed]
3. The Glaucoma Laser Trial Research Group. The Glaucoma Laser Trial (GLT) and glaucoma laser trial follow-up study: 7. Results. Am J Ophthalmol. 1995;120(6):718–731. [PubMed]
4. Lee R, Hutnik CM. Projected cost comparison of selective laser trabeculoplasty versus glaucoma medication in the Ontario Health Insurance Plan. Can J Ophthalmol. 2006;41(4):449–456. [PubMed]