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Editors Selection IGR 24-3

Surgical Treatment: SLT vs ALT in POAG

Comment by Tony Realini on:

55551 Selective laser trabeculoplasty versus argon laser trabeculoplasty in patients with open-angle glaucoma: a systematic review and meta-analysis, Wang W; He M; Zhou M et al., PLoS ONE, 2013; 8: e84270

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Wang and colleagues have recently conducted and reported a systematic review and meta-analysis of the relative efficacy and safety of selective laser trabeculoplasty (SLT) versus argon laser trabeculoplasty (ALT). Their analysis comprised six previously reported randomized clinical trials comparing these two treatment modalities in prospective, head-to-head fashion. Consistent with the findings of each of these individual studies, the combined meta-analysis demonstrated equivalent intraocular pressure (IOP)-lowering efficacy with these two treatment platforms, as well as equivalent safety profiles. With the benefit of only limited data for each laser system, the authors also concluded that repeatability of SLT and ALT were comparable, with similar IOP reductions at six months post-retreatment. These observations might lead one to ask what has driven the transition from ALT to SLT that has occurred in the US and globally over the past decade. There are several potential explanations. Firstly, SLT is technically easier to perform and to teach, by virtue of a 400-micron spot size compared to ALT's 50-micron spot size. Second is a portability factor for SLT (in its original design) which favored its use in multi-location practices. Third is the novelty factor ‐ we like new things. Fourth is a potential retreatment benefit. ALT is generally regarded as a one-off treatment.

Surprisingly, only scant data on repeatability of SLT has been published in the 13 years since its debut

ALT causes significant damage to trabecular cells, such that subsequent retreatments lead to cumulative damage and ultimately may cause reduction rather than improvement of trabecular outflow. The literature is replete with case reports of intractable IOP elevations following repeat ALT. Conversely, by virtue of a dramatically lower energy requirement, SLT causes minimal damage to trabecular cells, which in theory might allow safer repeat treatments. Surprisingly, only scant data on repeatability of SLT has been published in the 13 years since its debut. Of note, however, is that in that time there have been no reports in the literature of complications associated with repeat SLT that differ from primary SLT. While absence of evidence does not constitute evidence of absence, it is likely that intractable IOP elevations following repeat SLT are exceedingly uncommon. Overall, this meta-analysis confirms that ALT and SLT have much in common. Further well-designed research remains necessary to more fully characterize outcomes with both initial and repeat SLT and to better define its role in the long-term management of this chronic disease.

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