Bleb Needling in Trabeculectomy Revision

Bleb needling, an integral aspect of trabeculectomy revision, involves the lysis of scar tissue to restore the functionality of a blocked or scarred trabeculectomy. This procedure effectively reinstates aqueous outflow through a compromised filtration bleb and eliminates the need for a new surgery, thereby saving conjunctiva for future procedures. The improved aqueous outflow from a successful bleb needling can significantly lower intraocular pressure and reduces the risk of continued damage to the optic nerve. This report provides a detailed explanation of the bleb needling procedure, including its indications, contraindications, exploration of its advantages and possible complications.

Bleb needling candidacy is determined based on several criteria. Firstly, those who experience elevated intraocular pressures (IOPs) even after undergoing trabeculectomy surgery are considered for bleb needling. Secondly, individuals with seemingly non-functional blebs, characterized by flat or focal, dome-shaped appearances, unusual thickness or thinness, absence of microcysts, or abnormal vascularity around the bleb, are also eligible. Additionally, individuals whose IOP remains unresponsive to digital massage are considered for this procedure. Lastly, individuals without internal obstructions causing compromised outflow, as determined through gonioscopy, are identified as potential candidates for bleb needling1–4. There are several contraindications that determine the ineligibility for bleb needling. These include having an active ocular infection, extensive conjunctival or scleral thinning, presenting with diffusely scarred conjunctiva, and expected inability to adhere to the necessary postoperative care measures. In preparation for the procedure, a patient is positioned supine under sterile drapes. Topical anesthesia, usually a combination of proparacaine hydrochloride and tetracaine hydrochloride, is provided to the affected eye. A retro- or peri-bulbar block is typically administered given the occasional need for extensive sub-conjunctival manipulation with the needle. A lid speculum is placed to provide adequate exposure. The periorbital skin and ocular surface are cleaned with an antiseptic solution, reducing the risk of contamination. Cleaning of the surgical site with Povidone-iodine is proven to reduce the risk of endophthalmitis.

A 7-0 polyglactin corneal traction suture is used to rotate the eye to allow better access to the scarred bleb. The traction suture is placed horizontally in the superior cornea to rotate the eye inferiorly and allow access to the scarred bleb. The goal suture depth is about 50% of the cornea’s thickness. We want to avoid a full thickness bite as this creates an opening into the anterior chamber which can leak throughout the procedure. We also want to avoid a bite that is too superficial and causes a loss of traction. The suture can then be anchored to the eyelid speculum. A paracentesis incision is created and a 20- or 25-guage infusion canula is inserted through the wound into the anterior chamber to provide a continuous infusion balanced salt solution. This step will allow us to maintain the anterior chamber and visualize successful scar tissue disruption during the needling step (irrigation fluid will flow into the subconjunctival space). A 25- or 27-gauge needle is bent and then inserted superiorly, bevel-up into the sub-tenon space of the fibrotic scar tissue within the bleb. Gentle and controlled side to side sweeping motions are used to break scar tissue and restore aqueous outflow. The continuous flow of salt solution from the infusion canula should cause bleb elevation following the successful disruption of the scar blockage. In some cases, such as this one, it is necessary to insert the needle superonasally as well for further needling and adequate restoration of aqueous flow. Fibrosis can be identified and lysed at 3 levels: the subconjunctival space away from the trabeculectomy flap, at the flap itself, and under the flap. A reasonable approach is to work one’s way out to in, sometimes entering the anterior chamber under the flap to restore flow. An anti-fibrotic agent such as 5-fluorouracil (5-FU) or mitomycin-C (MMC) can be used to reduce the risk of post-needling fibrosis. 5-FU is likely preferable given concern for damage to anterior chamber tissues by MMC. To identify a post needling leak, surgeons can utilize fluorescein under cobalt light. Stromal hydration can be used to create swell the cornea at the infusion site.

Following the surgery, the patient had improved aqueous flow into the subconjunctival space and intraocular pressure in line with their target. Exploring the potential benefits and associated risks of bleb needling allows for a comprehensive understanding of its implications in the context of treating glaucoma. The primary advantage of this procedure is that it restores aqueous outflow through a formerly blocked or scarred bleb, and thereby helps to lower intraocular pressure and preserve the integrity of the optic nerve. The procedure is minimally invasive compared to alternative subsequent procedures such as a second trabeculectomy, the insertion of an aqueous shunt, or ciliary body ablation5. Bleb needling has proven to be effective at lowering IOP, with a recent meta-analysis of 2182 patients revealing that bleb needling produced an average decrease of IOP of 9.7 mmHg6. Despite its potential benefits, bleb needling comes with a range of potential rare complications. Achieving success in restoring the outflow pathway and lowering intraocular pressure (IOP) can vary due to factors like the extent of scarring and the time elapsed since the initial trabeculectomy. Potential complications can include the possibility of recurrent fibrosis, hyphema, infection, and hypotony resulting in flattening of the anterior chamber and choroidal effusion. Conjunctival buttonholes, characterized by defects in the conjunctival tissue that arise during manipulation of the conjunctival flap and may or may not involve the underlying Tenon's capsule, further underscore the range of possible complications associated with this procedure7. Furthermore, there are identified risk factors for an unsuccessful 5-fluorouracil (5-FU) needling revision, which include a pre-procedure IOP exceeding 30mmHg, needling of blebs that lacked the use of MMC in the initial filtration surgery, and achieving a post-needling IOP of 10mmHg8.

Alternatively, a bleb needling can be performed in an outpatient setting at the slit lamp. Benefits to doing bleb needling in the operating room include better visualization of the eye via the surgical microscope, and the availability of the anterior chamber infusion to determine when adequate bleb needling has occurred and aqueous outflow has returned.

Boland has consulted for Carl Zeiss Meditec, Topcon Healthcare, Allergan, and Janssen.

We have no acknowledgements to report.

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