The influence of treatment settings for SLT and ALT in the management of open angle glaucoma (OAG): a systematic review and meta-analysis

Abstract

 

Purpose

 

To study the relationship between various treatment settings for selective laser (SLT) and argon laser (ALT) trabeculoplasty in the management of OAG

 

Methods

 

A comprehensive literature search was performed of MEDLINE and Embase using the PRISMA guidelines. Prospective clinical studies published in English were eligible if they investigated SLT or ALT and reported mean IOP reduction at 6 or 12 months.

 

Results

 

There were 13 eligible studies each for the analysis of SLT and ALT (1,328 cases). The mean power settings reported were 0.79 (0.2 - 1.7) mJ for SLT and 725 (400 - 1500) mW for ALT. Majority of studies reported treatment that was 180 (18/29 study groups) or 360 degrees (8/29 study groups). The summary meta-analysis using a random effects model for both SLT and ALT revealed an IOP reduction at 6 months of 6.16 mm Hg (CI 4.83-7.49, 1,044 cases) and at 12 months of 5.89 mm Hg (CI 4.57-7.20, 1,122 cases). The meta-regression revealed no difference in ALT vs. SLT at 6 months (P=0.459) and 12 months (P=0.262). There was no evidence of publication bias. Meta-regression revealed an association between ALT’s minimum power (P < 0.001, P=0.046), maximum power (P < 0.001, P=0.046), and number of spots (P < 0.001, P=0.025) at 6 and 12 months respectively. There was no association with bubbling/blanching level versus IOP at 12 (P=0.931) months for ALT. SLT pressure reduction is significantly improved (P = 0.001) at 12 months by 2.25 mm Hg if used to a level of occasional or micro bubbling, as opposed to bubbling with every single spot. For SLT, there was no difference in 12 month IOP based on the minimum energy (P=0.127), maximum energy (P=0.863), number of spots (P=0.549), or degrees treated (P=0.451).

 

Conclusions

 

Increases in the power settings, number of spots, and degrees treated using ALT resulted in larger IOP reduction at 6 and 12 months. There was no association of IOP reduction with the visual endpoint for treatment with ALT; however with SLT IOP reduction is significantly improved at 12 months if used to a point of occasional or micro bubbling. SLT efficacy does not appear to be influenced by the range of power settings previously reported, or whether treatment is 180 versus 360 degrees.

 

 

Meta-analysis of combined SLT and ALT IOP reduction at (A) 6 months and (B) 12 months.

 

 

Begg’s funnel plot for data reported at (A) 6 months and (B) 12 months.

 

Keywords: 578 laser • 465 clinical (human) or epidemiologic studies: systems/equipment/techniques • 462 clinical (human) or epidemiologic studies: outcomes/complications