COMMENTARY

Laser Goniopuncture for Bleb Revision

Shuchi B. Patel, MD

Disclosures

April 30, 2014

Viewpoint

The postoperative course following trabeculectomy can be very unpredictable. Often, despite an uncomplicated surgery, there is still failure of the filtering bleb. Failure can occur as a result of obstruction to flow in many areas. One of the most common causes is subconjunctival fibrosis. Interventions such as needling procedures or surgical revisions are often necessary. Needling is an effective procedure to restore function of fibrotic blebs by lysing scar tissue, and reported rates of success vary from 7% to 69% for needling alone and increase to 75% to 94% for needling with concomitant administration of an antifibrotic agent (5-FU or mitomycin C).[1,2,3,4,5,6] But needling can have significant complications. Thus, in cases where the obstruction is elsewhere, if another technique could be employed that is less invasive, the complications could potentially be reduced.

LGP is a noninvasive, relatively simple technique to attempt to augment filtration, usually after a deep sclerectomy, by converting this noninvasive procedure to a full-thickness procedure with rupture of the trabeculo-Descemet membrane. The use of LGP has expanded to rescuing filtering blebs that are failing as a result of obstruction of the internal ostium. This particular study was unique in that LGP was used to reopen the pathway from the anterior chamber to the subconjunctival space in ischemic nonfunctioning blebs with visibly patent-appearing internal ostia. Yet, it did not include patients who had subconjunctival fibrosis, which, as mentioned previously, is often the cause of failure.

In this sample, the exact cause of resistance was unclear. One theory as to why the bleb morphology indicated more flow and the IOP declined after LGP is that the laser application promoted holes in the scleral flap, which is already weakened by the use of mitomycin C. This theory seems to be supported by the fact that the study did not include patients in whom the cause of failure was assumed to be conjunctival fibrosis. Similarly, a previous study found that ab interno trephination for bleb rescue was not successful in flat, scarred, or thickened blebs, whereas those exposed to mitomycin C and mobile conjunctiva showed better responses.[7]

Therefore, this technique shows promise in a class of bleb failures that excludes subconjunctival fibrosis as the cause of flow restriction. In those patients, needling or other techniques may be necessary. However, if there is mobile conjunctiva, LGP may provide a simple, noninvasive alternative to surgical intervention, given the low complication profile according to this study, which only had 2 cases of temporary hypotony. Further studies with more patients, as well as long-term follow-up, need to be done to determine true efficacy; but, as of now, LGP may be a viable option for a subpopulation of posttrabeculectomy patients with increasing IOP.

Abstract

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