Rapid and delayed death of cultured trabecular meshwork cells after selective laser trabeculoplasty

A Proposal for the Use of a Fixed Low-Energy Selective Laser Trabeculoplasty for Open Angle Glaucoma

Selective laser trabeculoplasty (SLT) has been in routine clinical use for over 20 years with millions of patients successfully treated and a low rate of clinically significant complications. The procedure requires the clinician to manually position the laser beam on the trabecular meshwork using a gonioscopy lens and to titrate the SLT laser energy based on the amount of pigmentation in the angle, as well as the observation of small bubbles produced by the laser effect. We propose that SLT energy titration is unnecessary either to achieve intraocular pressure (IOP) reduction or to minimize potential side effects. Ample evidence to support our proposal includes multiple clinical reports demonstrating comparable levels of IOP reduction resulting from different laser energies, a large variety of energy and other laser parameters used in commercially available SLT lasers, and the nature of the laser-induced changes in the trabecular meshwork tissue with respect to energy. Despite these variations in laser parameters, SLT consistently reduces IOP with a low complication rate. We propose that using low fixed energy for all patients will effectively and safely lower patients' IOP while reducing the complexity of the SLT procedure, potentially making SLT accessible to more patients.

Selective laser trabeculoplasty is safe and effective in patients previously treated with prostaglandin analogs: An evidence-based review

PURPOSE

Prostaglandin analogs (PGAs) are first-line treatments for ocular hypertension (OHT) and open-angle glaucoma (OAG). However, frequent side effects and high costs hinder patient's compliance resulting in disease progression. Evidence suggests selective laser trabeculoplasty (SLT) may be considered a first-line treatment for OHT and OAG due to its safety profile, minor side effects, and reduced costs. Considering that PGAs and SLT share action mechanisms, it is hypothesized that previous PGA therapy may affect subsequent SLT efficacy. Therefore, we analyzed if PGAs reduce SLT efficacy.

METHODS

An evidence-based review was performed to assess the safety and efficacy of SLT in patients previously treated with PGAs. For this purpose, we performed an extensive literature search using the National Library of Medicine's PubMed and Google Scholar database for all English language articles published until May 2021.

RESULTS

There is evidence of non-superiority of PGAs therapy versus SLT for OHT and OAG. A multicenter, randomized, observer-masked clinical trial (RCT) of untreated OHT and OAG patients concluded that SLT should be offered as the first-line treatment for these patients. This study was supported by a meta-analysis of RCTs, comparing SLT efficacy versus antiglaucoma drugs only, with the advantage of an SLT lower rate of adverse effects.

CONCLUSIONS

Cost-effectiveness, patient compliance, and antiglaucoma drugs' side effects, including higher surgical failure, favor consideration of SLT as first-line therapy for OAG and OHT. Furthermore, SLT efficacy does not seem to be affected by prior PGA administration; however, larger cohort, comparative, multicenter RCTs are necessary to answer this question.

A Review of Selective Laser Trabeculoplasty: "The Hype Is Real"

Presently, there is no efficacious treatment for glaucomatous optic neuropathy; the current treatment is focused on lowering intraocular pressure (IOP). Studies have demonstrated the safety and efficacy of selective laser trabeculoplasty (SLT) in reducing the IOP in eyes with open-angle (OAG) glaucoma or ocular hypertension (OH). Moreover, the European Glaucoma Society has instated SLT as the first-line or adjunctive treatment in OAG or OH, reiterating its clinical significance. In this review, we outline the old and the new roles of SLT, with an emphasis on clinical practice, and look further into its renewed appeal and future developments.

Low-energy Selective Laser Trabeculoplasty Repeated Annually: Rationale for the COAST Trial

The recent Laser in Glaucoma and Ocular Hypertension Trial provided the evidentiary basis for a paradigm shift away from the historical medication-first approach to glaucoma--which has numerous limitations, the most important of which is poor adherence to therapy --and toward a laser-first approach. Now 20 years after its commercialization, selective laser trabeculoplasty (SLT) is routinely performed consistently with its initial description, with energy titrated to the appearance of fine, champagne-like cavitation bubbles. A recent data set suggested that lower energy SLT, applied as primary therapy and repeated annually irrespective of intraocular pressure--rather than pro re nata when its effect wanes and irrespective of intraocular pressure rises --yields longer medication-free survival than standard energy SLT repeated pro re nata. A new study--Clarifying the Optimal Application of SLT Therapy --has been initiated to explore this preliminary finding in a pair of consecutive randomized trials. Herein, we provide an evidence-based rationale for the use of low-energy SLT repeated annually as primary therapy for mild to moderate primary open-angle glaucoma or high-risk ocular hypertension.

Feasibility of laser trabeculoplasty in angle closure glaucoma: a review of favourable histopathological findings in narrow angles

Selective laser trabeculoplasty (SLT) has been indicated as a safe and efficient treatment for primary open-angle glaucoma; however, recent studies have also shown positive results with the use of SLT in some clinical conditions related to primary angle-closure glaucoma (PACG). Despite the potential benefits of SLT in selected cases of PACG, the mechanisms underlying the modifications in the trabecular meshwork tissue of patients with PACG are poorly understood. This narrative review approached both the current, limited knowledge about the histological changes observed in different forms of PACG and the clinical results of SLT treatment for PACG. Favourable outcomes of SLT in patients with PACG, specifically in areas of non-occluded angle, need further substantiation through large controlled clinical trials. A deeper understanding of the biomolecular changes of those areas is essential to improve both laser technical details and the clinical efficacy of SLT therapy.

Complications of selective laser trabeculoplasty: a review

Selective laser trabeculoplasty is a laser treatment to treat glaucoma. It was initially indicated for open-angle glaucoma but has been proven to be efficacious for various types of glaucoma. This review article summarizes the few rare complications that can be seen with selective laser trabeculoplasty. It also makes recommendations on how to avoid these problems and how to treat patients when these rare complications arise.

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

BACKGROUND

Matrix metalloproteinases (MMPs) are reported to contribute to the mechanism of argon laser trabeculoplasty, but it is unknown whether they are also secreted after selective laser trabeculoplasty (SLT). The aim of this study was to investigate whether human primary trabecular meshwork (HTM) cells secrete MMP-3 after stimulation by SLT. The relationship between SLT and the two principal forms of cell death, apoptosis and necrosis, was also examined.

METHODS

Non-pigmented primary HTM cells were challenged with melanin granules to artificially introduce pigmentation. Isolated non-pigmented HTM cells and 1:1 co-cultures of pigmented and non-pigmented cells were treated with 0.5-1.5 mJ SLT. Cellular metabolic activity (CMA) was quantified using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptosis and necrosis were measured using a cell death ELISA and a lactate dehydrogenase assay, respectively. MMP-3 secretion was measured by ELISA.

RESULTS

Co-cultures exhibited a dose-dependent decline in CMA and a dose-dependent increase in necrosis 4 and 24 h after SLT. Non-pigmented cells did not undergo necrosis and displayed a trend towards increased CMA. Apoptosis was reduced in non-pigmented cells but elevated in co-cultures. Increased MMP-3 secretion was observed from co-cultures but not isolated non-pigmented cells.

CONCLUSIONS

Pigmentation is necessary for both post-SLT cell death and MMP-3 secretion. SLT appears to have a hormetic effect on non-pigmented HTM cells.

Mechanisms of selective laser trabeculoplasty: a review

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.

Acute transient corneal endothelial changes following selective laser trabeculoplasty

BACKGROUND

To report for the first time acute transient corneal endothelial changes following selective laser trabeculoplasty.

DESIGN

Observational case series at a tertiary referral ophthalmological centre in the United Kingdom (Addenbrooke's Hospital, Cambridge)

PARTICIPANTS

Ten consecutive routinely treated patients.

METHODS

Baseline measurements of corneal specular microscopy, endothelial cell counts and in vivo confocal microscopy were performed prior to routine selective laser trabeculoplasty treatment. Repeat measurements were made approximately 1 h later and at a 6-week follow up.

MAIN OUTCOME MEASURES

Endothelial in vitro laser confocal microscopy, specular microscopic endothelial cell count, endothelial morphology, visual acuity and intraocular pressure.

RESULTS

All patients had normal corneal endothelia prior to routine selective laser trabeculoplasty treatment, where 180 degrees of angle was treated. Approximately an hour afterwards, nearly all patients still had normal specular microscopy and cell counts (2237 ± 211 cells/mm(2) ) but had subtle endothelial changes on slit-lamp examination. These changes were found diffusely across the cornea. The changes were not present at the 6-week follow up and cell counts remained unchanged (2278 ± 242 cells/mm(2) ). Acuity remained unchanged throughout and the patients were not aware of these changes subjectively.

CONCLUSIONS

Selective laser trabeculoplasty appears to cause transient corneal endothelial changes in most patients that have no impact on cell count or visual acuity. Further work is required to elucidate the mechanism of this phenomenon and any long-term impact.

Apoptosis in the iris and trabecular meshwork of medically treated and untreated primary open angle glaucoma patients

AIM

To compare the trabecular meshwork (TM) and iris apoptosis of treated and untreated primary open angle glaucoma (POAG) patients.

METHODS

Eight treatment-naive, newly diagnosed (group 1) and 11 medicaly treated (group 2) patients with POAG were included in the study. Each patient underwent a limbus-based trabeculectomy. The TM and peripheral iris specimens were dissected out and were snap-frozen in liquid nitrogen and stored at -80°C until they were assayed. Apoptosis in each group was assesed by TUNEL method.

RESULTS

The mean patient age was 60.6±5.8 years (53-68 years) vs 58.9±8.9 years (47-70 years) in group 1 and group 2 (P=0.859). The mean treatment time in group 2 was 22.2±7.3 months (12-34 months). Apoptotic indexes in TM and iris were significantly higher in POAG patients using medication (group 2) compared to treatment-naive POAG patients (group 1) (P=0.004, 0.015; respectively).

CONCLUSION

Long term administration of topical antiglaucoma medications causes additional toxic effects on TM.

Trabecular meshwork gene expression after selective laser trabeculoplasty

BACKGROUND

Trabecular meshwork and Schlemm's canal are the tissues appointed to modulate the aqueous humour outflow from the anterior chamber. The impairment of their functions drives to an intraocular pressure increase. The selective laser trabeculoplasty is a laser therapy of the trabecular meshwork able to decrease intraocular pressure. The exact response mechanism to this treatment has not been clearly delineated yet. The herein presented study is aimed at studying the gene expression changes induced in trabecular meshwork cells by selective laser trabeculoplasty (SLT) in order to better understand the mechanisms subtending its efficacy.

METHODOLOGY/PRINCIPAL FINDINGS

Primary human trabecular meshwork cells cultured in fibroblast medium underwent selective laser trabeculoplasty treatment. RNA was extracted from a pool of cells 30 minutes after treatment while the remaining cells were further cultured and RNA was extracted respectively 2 and 6 hours after treatment. Control cells stored in incubator in absence of SLT treatment were used as reference samples. Gene expression was evaluated by hybridization on miRNA-microarray and laser scanner analysis. Scanning electron microscopic examination was performed on 2 Trabecular meshwork samples after SLT at 4(th) and 6(th) hour from treatment. On the whole, selective laser trabeculoplasty modulates in trabecular meshwork the expression of genes involved in cell motility, intercellular connections, extracellular matrix production, protein repair, DNA repair, membrane repair, reactive oxygen species production, glutamate toxicity, antioxidant activities, and inflammation.

CONCLUSIONS/SIGNIFICANCE

SLT did not induce any phenotypic alteration in TM samples. TM is a complex tissue possessing a great variety of function pivotal for the active regulation of aqueous humour outflow from the anterior chamber. SLT is able to modulate these functions at the postgenomic molecular level without inducing damage either at molecular or phenotypic levels.