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Editors Selection IGR 7-2

Surgical Treatment: Morphological changes after deep sclerectomy

Comment by Stefano Gandolfi on:

55564 Visante anterior segment optical coherence tomography analysis of morphologic changes after deep sclerectomy with intraoperative mitomycin-C and no implant use, Pérez-Rico C; Gutiérrez-Ortíz C; Moreno-Salgueiro A et al., Journal of Glaucoma, 2014; 23: e86-e90

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More than two decades have elapsed since Thom Zimmermann described a new technique he named 'non-penetrating trabeculectomy', leading to external limbal filtration and IOP drop in open-angle glaucomas.¹ However, there still is a significant debate on some presumed landmarks for obtaining successful surgeries, as well as on the ultimate explanation on how and why deep sclerectomy works.

As early as in the year 2001, Marchini and co-workers, by applying UBM on eyes operated with deep sclerectomy + re-absorbable hyaluronic acid implant, suggested three possible mechanisms for IOP reduction, namely: (a) external subconjunctival filtering bleb; (b) increased uveoscleral outflow; and @ transcleral filtration.² The authors were also warning of the dynamic nature of the so-called 'intra-scleral lake', measuring a significant decrease in size as early as six months after surgery. Shortly thereafter, these results were confirmed by Kazakova and co-workers, whose retention of a measurable intrascleral lake was slightly higher.³ The potential impact of the presence (and, in some cases, the size) of an intrascleral decompression chamber on the long-term success of deep sclerectomy was then investigated with controversial results.^4,5 The work of Perez-Rico and co-workers offers additional food for thoughts. Their data clearly show that (a) a scleral lake can be detected in the vast majority of eyes (in their case series, in every eye) operated with DS as long as five years after surgery; (b) the use of an implant is not mandatory to maintain a patent scleral lake in the long term; @ the biometry of the scleral lake can vary among individual eyes; (d) external effective subconjunctival filtration, as measured by the presence of a low-reflectivity in the bleb tissue, is a main drive to complete post-operative success.

Unfortunately, while correlating the biometry of the scleral lake with the IOP, the authors merged IOP data with and without topical anti-glaucoma medications

Unfortunately, while correlating the biometry of the scleral lake with the IOP, the authors merged IOP data with and without topical anti-glaucoma medications. Therefore, their data, suggesting a possible inverse relationship between the size of the scleral lake and post-operative long-term IOP, meanwhile extremely interesting, are still not completely conclusive.

In conclusion, the race to fully understand the mechanisms of action of deep sclerectomy is still ongoing but, after the work by Perez-Rico and colleagues, more insights are now available.

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