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Editors Selection IGR 20-1

Surgical Treatment: Predicting long-term outcome of sub-Tenon needle revision

Comment by Syril Dorairaj on:

48383 Use of ultrasound biomicroscopy to predict long-term outcome of sub-Tenon needle revision of failed trabeculectomy blebs: a pilot study, Kaushik S; Tiwari A; Pandav SS et al., European Journal of Ophthalmology, 2011; Mar 22; 21: 700-707

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This prospective, comparative study aims to evaluate the role of ultrasound biomicroscopy (UBM) in predicting the long-term outcome of sub-Tenon needling revision of failed trabeculectomy blebs, correlating with the presence of aqueous out flow in sclera. Based on UBM, Kaushik et al. (1913) classified the blebs into two groups, scleral route patent (SRP) or scleral route occluded (SRO). They conclude that only SRP blebs have a long-term survival and blebs with SRO need full revision rather than needling alone. The study results demonstrate that UBM is a potentially useful modality to predict surgical failure after trabeculectomy and gives out important information to look out for scleral route patency while planning for revision. Authors included patients with patent internal sclerostomy visualized on gonioscopy and acquired radial scans to visualize the patency of the scleral route. It should be noted that there is a possibility that the scleral routes may not always be picked up on radial scans since some of them may also run as tributaries and can only be picked up through transverse scans, which the authors didn't perform on their patients.

Scleral routes may not always be picked up on radial scans since some of them may also run as tributaries and can only be picked up through transverse scans

Finding these variable subsidiary routes is an important characteristic that would distinguish the morpholological features after successful needling especially in patients who had a successful outcome in the SRO group. Interestingly the study conclusions match previous reports, which documented better IOP control if bleb morphology revealed fluid under the scleral flap.

Kaushik et al. also concluded that there was no difference in age, IOP, and time from initial trabeculectomy between the failed and successful group. However, it should be noted that long-term success of trabeculectomy is dependent on the wound healing and sub conjunctival scarring and it may vary with age and type of glaucoma. Since authors have included patients with wide age and IOP range, and with varied etiology of glaucoma, this conclusion needs to be validated in future larger prospective studies which would also be able to look into the odds ratio of success of other preoperative factors such as pre-needling IOP, age, type of glaucoma, and surgical factors of the prior trabeculectomy. This could be achieved not only through UBM but also with newer AS-OCT devices, which give better images with higher resolution in three dimensions and can be more comfortable to the patients. It is imperative to evaluate the bleb morphology and characteristics, since trabeculectomy is still considered a gold standard in managing glaucoma patients and needle revision with adjunctive anti-metabolites is an effective modality for re-establishing filtration in failed blebs.

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