Predictors of success in selective laser trabeculoplasty for normal tension glaucoma

Selective laser trabeculoplasty: An updated narrative review

Selective laser trabeculoplasty (SLT) has experienced a resurgence in interest, primarily driven by promising findings from the Laser in Glaucoma and Ocular Hypertension Trial. By offering SLT as an initial drug-free treatment option, we may be able to thwart issues such as adherence and persistence that plague our current medical management protocols. In this comprehensive narrative review, we delve into the current body of literature that explores the utility of SLT across a wide spectrum of scenarios and glaucoma subtypes. We present evidence that provides valuable insight into the efficacy and benefits of SLT, positioning it as a viable option in the management of glaucoma. Careful consideration of the associated risks and challenges is also necessary for successful adoption into clinical practice. Despite the ample evidence supporting SLT's efficacy, some questions remain regarding its long-term effects and the potential need for retreatment. This review aims to shed light on these aspects to guide clinicians in making informed decisions and tailoring treatment plans to individual patient needs. This review also provides the readers with a bird's eye view of the potential impact of SLT and adds clarity to the various therapeutic protocols that one can follow to ensure optimal clinical outcomes for our patients.

Identifying Baseline Predictors of Selective Laser Trabeculoplasty Effectiveness: An Alternative Mathematical Approach

BACKGROUND

Selective laser trabeculoplasty (SLT) emerges as a first-line treatment for newly diagnosed open-angle glaucoma and ocular hypertension. However, the interindividual response to SLT considerably varied. Large-scale clinical investigations concerning predictive factors for SLT effectiveness are limited. This study aimed to identify baseline predictors of the percentage intraocular pressure (IOP)-lowering effectiveness of SLT using an alternative mathematical approach.

METHODS

Mathematical equations of IOP under the steady state of aqueous humour flow were formulated. The conclusive equation integrates physiological variables, including trabecular outflow facility, uveoscleral outflow fraction, plasma protein concentration, albumin/globulin ratio, mean arterial pressure, episcleral venous pressure, and plasma osmolarity. The equation was employed to estimate the percentage of IOP reduction following SLT and subsequently subjected to global sensitivity analysis to determine significant predictors of the IOP-lowering effect of SLT using the Monte Carlo simulation of 8,192 samples.

RESULTS

In the current model, a 50% improvement in the trabecular outflow facility impacted by SLT is associated with a mean percentage IOP reduction of 16.6%. Lower baseline trabecular outflow facilities were the strongest predictors, showing a correlation with greater effectiveness of SLT in terms of percentage of IOP reduction. The second most influential factor includes baseline uveoscleral outflow fraction, followed by baseline episcleral venous pressure. Specifically, lower baseline uveoscleral outflow fraction and episcleral venous pressure were found to be correlated with increased effectiveness of SLT. Baseline levels of plasma protein concentration, albumin/globulin ratio, mean arterial pressure, and plasma osmolarity have minimal impact on SLT success or failure.

CONCLUSION

This study identifies baseline trabecular outflow facilities as the strongest predictor of SLT effectiveness. The results suggested that pre-SLT medical treatment that augments uveoscleral outflow and/or trabecular outflow facilities could compromise the effectiveness of subsequent SLT in terms of percentage IOP reduction compared to those who never received pre-SLT medication.

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.

Selective laser trabeculoplasty: A review

Glaucoma is the second most prevalent cause of blindness worldwide, and the only effective management is the lowering of intraocular pressure (IOP). Selective laser trabeculoplasty (SLT) has become an essential part of glaucoma management since its commercial release in 2001. It has been an improvement from the previous argon laser trabeculoplasty (ALT), by using 1% of the laser energy, reducing the amount of anterior segment inflammation and minimising the degree of mechanical injury to the trabecular meshwork. There is now a large volume of work that demonstrates SLT is equally effective as ALT and topical medication in lowering IOP. It is simple to perform, with a well described side-effect profile, and is long-lasting and repeatable. This review will summarise the current literature on SLT for each of these topics.

Predictive Factors for Outcomes of Selective Laser Trabeculoplasty

We sought to  determine predictive factors for selective laser trabeculoplasty (SLT) outcome. 252 eyes from 198 adult patients with open-angle glaucoma who underwent SLT between July 2016 and February 2018 with a minimum 6 month follow up were reviewed. We defined success as ≥20% IOP reduction or ≥1 medication reduction without an IOP lowering procedure. We also evaluated the relationship of these factors to postoperative IOP elevation >5 mmHg (IOP spikes). Our primary outcome measure was association between age, type and severity of glaucoma, pigmentation of the trabecular meshwork (PTM), total energy delivered, and baseline intraocular pressure (IOP) with success. At 2 and 6 months, 33.6% (76/226) and 38.5% (97/252) of eyes met success criteria respectively. Baseline IOP > 18 mmHg was significantly associated with success both at 2 and 6 months, reducing IOP by 5.4 ± 5.3 mmHg (23.7% reduction), whereas those with lower baseline remained at −0.7 ± 4.6 mmHg (4.9% increase) at 6 months (P < 0.001). No other baseline characteristics significantly predicted success or IOP spikes. Patients with higher baseline IOPs had greater success rates and mean IOP reduction at both 2 and 6 months following SLT. Age, type and severity of glaucoma, PTM, or total energy delivery had no association with procedural success or IOP spikes. Patients with higher baseline IOP may experience greater lowering of IOP after SLT. However, SLT may be equally successful for patients with a variety of other characteristics.

Predictors of Outcome in Selective Laser Trabeculoplasty: A Long-term Observation Study in Primary Angle-closure Glaucoma After Laser Peripheral Iridotomy Compared With Primary Open-angle Glaucoma

PURPOSE

To evaluate the efficacy of selective laser trabeculoplasty (SLT) for patients with primary angle-closure glaucoma (PACG) following a YAG laser peripheral iridotomy (PI) in comparison with primary open-angle glaucoma (POAG) and to assess the predictors of outcome of SLT.

PATIENTS AND METHODS

In retrospective study 68 patients with PACG after PI (68 eyes) and 74 POAG patients (74 eyes) were observed for 6 years. The effectiveness of SLT (20% reduction of intraocular pressure) was assessed using Kaplan-Meier survival analysis. The parameters for distinguishing the eyes with success and failure of SLT were detected by means of area under receiver operating characteristic curve (AUC). The predictive factors affecting SLT outcome were determined using Cox-regression analysis.

RESULTS

The success ratio was 87% in both groups in 1 year and dropped to 4% in PACG and to 6% in POAG in 6 years. Corneal hysteresis [odds ratio (ОR)=0.367, Р=0.005 for PACG, ОR=0.446, Р=0.008 for POAG] and age (OR=1.182, P=0.012 for PACG, OR=1.164, P=0.002 for POAG) were detected as the predictors of SLT outcome. In PACG pre-SLT anterior chamber depth was additional predictor (ОR=0.242, Р=0.001). The number of pre-SLT pressure-lowing medications was higher in the eyes with SLT failure (AUC, 0.794; P=0.0005 in PACG and AUC, 0.760; P=0.014 in POAG).

CONCLUSIONS

One-year efficacy of SLT in POAG and PACG after PI was high, but it was reduced in long-term period. Corneal hysteresis, age, and number of pre-SLT hypotensive eye drops were significant prognostic factors for treatment success in both glaucoma forms. In PACG pre-SLT anterior chamber depth affected the SLT outcome.

New approaches to selective laser trabeculoplasty

Selective laser trabeculoplasty (SLT) is the “golden standard” of laser glaucoma surgery. Its efficacy can be compared to pharmacological therapy, while in some cases its advantages may even lead to a more stable hypotensive effect. SLT may be used as a primary treatment for primary open-angle glaucoma patients and patients with ocular hypertension, while also considered safe and effective in cases when a repeat procedure is required. SLT may potentially decrease the demand for antiglaucoma drugs, improve patient’s response to treatment, make the treatment more comfortable and overall increase the patient’s quality of life. New modifications of standard laser treatment procedures have been emerging lately. This article summarizes scientific data on the efficacy and safety of the new generation of laser trabeculoplasty. It specifies the charateristics of micropulse laser trabeculoplasty (MLT), pattern-scanning trabeculoplasty (PLT) and titaniumsapphire laser trabeculoplasty (TSLT) and recounts the latest research dedicated to them.

Selective laser trabeculoplasty in pseudophakic and phakic eyes: a prospective study

AIM

To compare the efficacy of selective laser trabeculoplasty (SLT) in replacing medical therapy in pseudophakic and phakic eyes.

METHODS

Subgroup of a prospective randomized clinical trial including patients with primary open angle glaucoma or ocular hypertension controlled with medication. Of 38 pseudophakic eyes were matched with 38 phakic eyes. SLT was offered as a way to decrease medication while maintaining the same low eye pressure. SLT was performed over 360°, at 3ns, spotsize 400 µm, 100 spots. Data [intraocular pressure (IOP), number of medications needed] were measured at 1h, 1wk, 1, 3, 6 and 12mo. An independent-samples t-test was performed to compare baseline characteristics of the phakic and the pseudophakic group and differences in evolution of mean IOP and number of used medications. Chi-squared analysis was performed to investigate proportions of fast, slow and non-responders.

RESULTS

The mean IOP measurement was 13.00± 2.88 mm Hg in the phakic group (38 eyes) and 13.51±3.06 mm Hg in the pseudophakic group (38 eyes) (P>0.05). This changed little after SLT and IOP lowering effect was comparable between the two groups. Main aim however was to lower the amount of medication needed. In the phakic group medication lowered from 1.29±0.62 at baseline, to 0.15±0.46 after 12mo; a reduction of 88.37%. In the pseudophakic group, used medication changed from 1.71±1.04, to 0.41±0.61; a 76.02% reduction. The differences were not statistically significant at any time point (P>0.05). IOP lowering occurred slightly faster in the pseudophakic group (50% of patients after one week) than in the phakic group (68% of patients after more than 4wk). The difference was not significant (P>0.05).

CONCLUSION

IOP lowering effect of SLT is comparable between phakic and pseudophakic eyes.

Preoperative intraocular pressure as a predictor of selective laser trabeculoplasty efficacy

PURPOSE

To identify predictors of intraocular pressure (IOP) reduction following selective laser trabeculoplasty (SLT) in patients with high- and low-pressure primary open-angle glaucoma, who are already taking maximally tolerated IOP-lowering medication and need further IOP reduction.

METHODS

In this prospective interventional case series, 157 eyes of 157 open-angle glaucoma patients who were assigned for SLT for further IOP reduction were included. Each patient had diurnal IOP measurements taken before and on average 6 months following SLT. The mean of six IOP measurements was compared. The following parameters were analysed for their association with SLT success: age, gender, spherical equivalent, high-pressure or normal-pressure open-angle glaucoma, number and type of pressure-lowering medications, lens status, pre-SLT IOP, IOP at the time of diagnosis, duration of glaucoma, visual field stage and central corneal thickness.

RESULTS

The only parameter that was predictive for absolute and relative mean diurnal IOP reduction after SLT was the preoperative mean diurnal IOP. One hundred per cent of the patients with a mean diurnal preoperative IOP of more than 18 mmHg had an IOP reduction after SLT. With mean diurnal preoperative values of 14-18 mmHg, 83.1% of the patients, and with values below 14 mmHg only 64% of the patients, showed an IOP reduction. This difference was statistically significant (>18 compared to 14-18: p = 0.002; >18 compared to <14: p = 0.001; 14-18 compared to <14: p = 0.030).

CONCLUSIONS

The pressure-lowering effect of SLT can best be predicted by the individual IOP level before treatment. Patients with mean diurnal IOP levels below 14 mmHg might not benefit from the procedure at all.

Selective Laser Trabeculoplasty: An Update

Selective laser trabeculoplasty (SLT) is an effective treatment option for the reduction of intraocular pressure (IOP) in patients with ocular hypertension or open-angle glaucoma. The mechanism by which SLT lowers IOP is not completely understood and is likely multifactorial. Published studies indicate that SLT is at least as effective as argon laser trabeculoplasty or medications at lowering IOP in many forms of glaucoma. In addition to IOP reduction, SLT may decrease IOP fluctuation and can be successfully used as primary or adjunctive therapy for the management of both early and advanced glaucoma. However, SLT may not be effective in certain forms of glaucoma, and the IOP-lowering effect seems to wane with time. High pretreatment IOP is the strongest predictor of treatment success, even in patients with normal-tension glaucoma. Repeatability of SLT has been controversial, but recent evidence suggests that it can be successfully repeated to achieve additional or recurrent IOP reduction, even in eyes that only had a modest response to initial treatment. Adverse events are uncommon after SLT, and the most common complications such as discomfort and inflammation are typically mild and transient. Further investigation is required to determine the optimal treatment parameters for SLT treatment. Limited evidence suggests that SLT is cost-effective as primary therapy for patients with glaucoma.

MicroPulse Laser Trabeculoplasty for the Treatment of Open-Angle Glaucoma

The aim of the study was to investigate the safety and efficacy of using MLT in the treatment of open-angle glaucoma (OAG).This prospective cohort included subjects ≥18 years of age with OAG, defined as the open angle on gonioscopy with glaucomatous optic neuropathy evident from optical coherence tomography. Subjects with IOP < 21 mm Hg were classified as normal tension glaucoma and those with IOP ≥21 mm Hg were classified as primary open-angle glaucoma. Those with angle closure, secondary glaucoma, prior laser trabeculoplasty, use of systemic IOP-lowering medications, corneal pathologies, follow-up <6 months, recent intraocular surgery, or only 1 functional eye were excluded. A single session of unilateral MLT treatment was delivered using a 577 nm diode laser to 360° of the trabecular meshwork to reduce IOP or medication load. Medications were titrated up or down at 1 month after laser to achieve a 25% IOP reduction from presentation or an IOP <18 mm Hg, whichever was lower. The following were compared using the Repeated Measures ANOVA with Bonferroni's Multiple Comparison Test: IOP (on presentation, pre-MLT, day 1, 1 week, 1 month, 3 months, and 6 months after MLT) and the number of medications (pre-MLT, 3 months, and 6 months after MLT). After 6 months, responders with initial success to MLT (IOP reduction ≥20% at 1 month) received treatment in the fellow eye.In 48 subjects with OAG, the mean number of MLT shots applied was 120.5 ± 2.0 shots using a mean energy of 1000 mW per shot. Only 7.5% had a mild, self-limiting anterior uveitis postlaser with no change in the Snellen visual acuity at 6 months (P's > 0.5). The IOP and number of medications were significantly reduced at all time intervals following MLT compared to the pre-MLT level (P's < 0.0001). At 6 months, the IOP was reduced by 19.5% in addition to a 21.4% reduction in medication compared to pretreatment levels. The MLT success rate was 72.9%. During the first 6 months only 2.1% required a repeated laser trabeculoplasty.MLT was effective in reducing IOP and medications in OAG with minimal postlaser inflammation and low failure rate at 6 months following laser.

[Current aspects on the management of normal tension glaucoma]

In a considerable proportion of glaucoma patients (25-50 %) the intraocular pressure (IOP) is not elevated higher than 22 mmHg at first diagnosis and during subsequent follow-up controls. Although the IOP level remains in the low range < 22 mmHg, progression of glaucoma can still occur. A multitude of different factors are assumed to be involved in glaucoma progression, such as very low nocturnal diastolic blood pressure values, a low mean ocular perfusion pressure, extensive fluctuations in perfusion (e.g. in cases of vascular dysregulation), an increased vulnerability of the optic nerve support structures, an increased translaminar pressure gradient and various underlying systemic diseases. The most important evidence-based aspect of treatment in normal tension glaucoma is pharmaceutical or surgical reduction of the IOP by 30 % or more in comparison to the initial pressure level. Vascular and neuroprotective concepts of treatment for normal tension glaucoma have been strongly advocated and the object of experimental and clinical studies. As yet a clear clinical benefit has not been proven by large prospective randomized studies.

Two-Year Clinical Results After Selective Laser Trabeculoplasty for Normal Tension Glaucoma

This article aims to investigate the clinical results at 2 years after selective laser trabeculoplasty (SLT) for normal tension glaucoma (NTG). This prospective cohort study recruited NTG patients taking antiglaucoma medication. Subjects were excluded if they had previous glaucoma surgery/laser or corneal pathologies. All subjects underwent a 1-month washout. A single session of SLT was performed to 360° of the trabecular meshwork. Medication was resumed at 1 month to achieve a targeted 30% intraocular pressure (IOP) reduction from the post-washout/pre-SLT IOP. IOP was measured every 3 months and medication use was recorded at 3, 6, 12, and 24 months. Subjects with a secondary SLT or cataract extraction were excluded from IOP and medication analyses. At 24 months, 34 of the initial 45 right eyes were eligible for analyses. There were significant IOP reductions at all time intervals (except at 1 week) following SLT when compared to the prestudy (without medication) or pre-SLT (post-washout) IOP (P < 0.0001). Medications were likewise significantly reduced at all time intervals following SLT (P < 0.0001). At 24 months, the IOP was 11.5% lower than the prestudy IOP, 22.0% lower than the pre-SLT IOP, and medication use was reduced by 41.1% (P < 0.0001). Six out of 45 eyes (13.3%) required a secondary SLT. Absolute success (IOP reduction >20% from pre-SLT, without medication) was achieved in 11.1% (5/45). Reductions in IOP and medication use were evident at 2 years following SLT for the treatment of NTG whereas 11% remained medication free.

TRIAL REGISTRATIONS

The Clinical Trials Register of the University of Hong Kong HKCTR1847. The European Clinical Trials Database 2014-003305-15 (August 11, 2014).