Whitepapers and Tech Notes:
SLT: The Duality of SLT in Glaucoma Management
This whitepaper explores the diagnostic and treatment roles of selective laser trabeculoplasty (SLT) in glaucoma management. Whilst many studies have reviewed the evidence for SLT as a primary or adjunct therapy, the benefit derived from SLT as a diagnostic aid when used as first-line therapy is something that is only now beginning to be explored. One of the biggest challenges in managing glaucoma is accurately determining the location of blockages within the outflow system.
SLT works by applying selective photothermolysis to the pigmented trabecular meshwork cells, releasing proteins and cytokines which improve the circulation of aqueous humor through the trabecular meshwork and the inner wall of the Schlemm’s canal. This mechanism of action allows physicians to estimate the location of the pathology based on the outcome of SLT: if SLT is effective, the physician can deduce that the primary region of obstruction lies within the trabecular meshwork. In contrast, if SLT proves ineffective, then the primary obstruction may reside outside the trabecular meshwork. Not only is this helpful in understanding the patient’s pathology, but it can also provide key information regarding the potential efficacy of future treatments.
SLT: A Comprehensive Treatment Solution for Glaucoma
In this whitepaper, Savak Teymoorian, MD, MBA, Harvard Eye Associateds, discusses the role of SLT across the glaucoma treatment algorithm. According to Dr. Teymoorian, the use of SLT as a primary therapy has slowly taken hold since its US introduction in 2001. Today, an increasing number of glaucoma specialists and general ophthalmologists view SLT as a viable alternative to medications in patients with newly diagnosed glaucoma. He also believes that an increasing number of general ophthalolmogists will come to perform SLT, owing to the growing burden of glaucoma: “A general ophthalmologist can easily learn how to do SLT. If a surgeon can do a capsulotomy, then they can do SLT. Actually, SLT is easier because it doesn’t involve any cutting,” says Dr Teymoorian. “All general ophthalmology practices should have an SLT laser.”
In most POAG patients, SLT reduces IOP significantly for a few years without any major or permanent side effects or complications. Consequently, the idea of potentially gaining some drug-free years for a newly diagnosed patient by using SLT as the initial therapy is appealing.
Non-thermal, SLT does not cause any collateral damage or burn to surrounding tissues and the trabecular meshwork structure. This unique clinical effect allows SLT to be repeated.
Angle Closure Glaucoma
Primary angle closure glaucoma (PACG) occurs when the outer part of the iris bulges forward and touches the back of the cornea, inhibiting the outflow of fluid. With PACG immediate treatment is required in order to save the optic nerve, and consists of creating a hole in the iris periphery to allow the outflow of fluid.
Normal Tension Glaucoma
The Normal Tension Glaucoma (NTG) Study Group reported that a 30 percent reduction in IOP can be attained in most NTG eyes with a combination of drugs and ALT. It can therefore be assumed that SLT will achieve similar IOP lowering results in NTG, with the added benefit of repeatability, and without the side effects associated with ALT.
Pigment Dispersion Glaucoma and Eyes with Highly-Pigmented Trabeculum
One of the main theories on the mode of action in SLT is that the laser energy is absorbed in melanin granules in the trabeculum, which triggers a biological response that effectively reduces IOP. If this is indeed the case, the results of SLT treatment should vary according to the degree of pigmentation of the trabecular meshwork.