Mechanisms of selective laser trabeculoplasty: a review

Abstract

Selective laser trabeculoplasty is a safe and effective treatment for glaucoma, with greater cost effectiveness than its pharmacological and surgical alternatives. Nevertheless, although the basic science literature on selective laser trabeculoplasty continues to grow, there remains uncertainty over the mechanism by which laser trabeculoplasty reduces intraocular pressure. To address this uncertainty, the evidence behind several potential biological and mechanical mechanisms of selective laser trabeculoplasty were reviewed. In particular, cytokine secretion, matrix metalloproteinase induction, increased cell division, repopulation of burn sites and macrophage recruitment were discussed. Refining our understanding of these mechanisms is essential both to understanding the pathophysiology of ocular hypertension and developing improved therapies to treat the condition.

Secretion of matrix metalloproteinase‐3 by co‐cultured pigmented and non‐pigmented human trabecular meshwork cells following selective laser trabeculoplasty

“…The rapid expansion due to heat, confined within pigmented cells, leads to destruction of the intracellular architecture with subsequent cell death. This occurs while preserving adjacent cells from collateral thermal damage . Consequently, although it is as effective at reducing intraocular pressure (IOP) as traditional argon laser trabeculoplasty (ALT), data have supported SLT as a safer alternative because it does not induce widespread disruption and photocoagulation of surrounding ocular tissues like its precursor …”

“…Although the clinical benefits of SLT are well established, the IOP‐lowering mechanisms of SLT are not completely understood . The ‘biological theory’ posits that initial cellular injury and death caused by the laser induce alterations in gene expression and secretion of cytokines and molecular factors that affect the surrounding HTM cells.…”

A comparison of clinical trial and model-based cost estimates in glaucoma – The case of repeat laser trabeculoplasty In Ontario

“…The precise mechanisms by which SLT reduces IOP are not fully understood, but it is thought to induce a suite of biological mechanisms that act to augment trabecular outflow, as opposed to the putatively mechanical effects of ALT. [1] A consequence of SLT's non-destructive mechanism of action is that it is, in theory, repeatable. If so, its utility is considerable.…”

Selective laser trabeculoplasty as an initial treatment option for open-angle glaucoma

“…Argon laser trabeculoplasty (ALT) was first described in 1979 (Table 1) (11) . The laser uses a blue-green (488 and 514 nm) continuous wave argon laser with a 50 μm spot diameter and makes a disruption of the trabecular meshwork (12,13) . In 1995, selective laser trabeculoplasty (SLT) was described.…”

“…In 1995, selective laser trabeculoplasty (SLT) was described. This melanin-target tissue sparing procedure uses a green (532 nm), Q-switched, frequencydou bled Nd:YAG laser (13) . It is important to emphasize that ordinary YAG laser devices, commonly used for iridotomy or capsulotomy, cannot be used to perform SLT.…”