Late bleb leaks are more frequently encountered in thin, avascular blebs that were exposed to antifibrotic agents at the time of surgery.1-5 Leakage of the filtering bleb can be associated with hypotony and increases the chances for bleb-related infection and endophthalmitis.3,5,6 A surgeon must be able to differentiate between a bleb leak (ie, through a hole in the bleb) and bleb ooze (also known as a sweating bleb), which represents transconjunctival flow commonly seen in ischemic, thin blebs.
Bleb leaks may resolve spontaneously, and late bleb leaks may leak intermittently from new sites.
DIAGNOSIS
A Seidel sign will detect a leaking bleb (Figure 1). The surgeon applies a fluorescein strip to the inferior tarsal conjunctiva or, very gently, directly to the bleb. Without applying pressure, he should examine the eye under cobalt blue illumination. If there is a leak, he will see unstained aqueous humor flowing into the tear film. If there is no spontaneous leakage, the ophthalmologist should gently apply pressure to the globe or bleb while examining the suspicious area.
Figure 1. A Seidel sign detects a leaking bleb.
EARLY BLEB LEAKS
Management
The need for and timing of surgical intervention depends on the severity of the leakage and presence of complications. A brisk leak associated with a flat filtering bleb, ocular hypotony, and a shallow-to-flat anterior chamber merits prompt treatment. If the leak is mild, however, with an elevated bleb, an acceptable IOP, and a deep anterior chamber, it is permissible to observe the patient in order to allow time for the leak possibly to close spontaneously. In this case, it is advisable to discontinue or reduce the amount of topical steroids that the patient receives.
Therapeutic modalities to treat early leaking blebs include pressure patching, a bandage contact lens, Simmon's shell, a symblepharon ring, fibrin tissue glue, cyanoacrylate glue, and surgical revision.7 The last option is the most efficient.8
Surgical Techniques for Repair
If the leak is located in the center of the conjunctival flap, the surgeon may attempt a purse-string closure either internally on the undersurface of the conjunctiva or externally overlying the flap, if the flap has already been reapproximated. A 10–0 or 11–0 nylon on a tapered (“vascular”) needle should be used. When the conjunctival buttonhole or tear occurs at the limbus, it may be sutured directly to the cornea, which should be de-epithelialized. A mattress suture or, if large, a running suture with 10–0 nylon is appropriate. When the buttonhole or tear occurs near the incised edge of a limbal-based conjunctival flap, the surgeon may place sutures to close the conjunctival incision anterior to the tear to close it as well.
LATE BLEB LEAKS
Management
The need for and timing of intervention for late bleb leaks depends on several factors. For instance, monocular individuals with leaking blebs who have had previous episodes of bleb-related infections, persistent ocular hypotony, a persistently shallow-to-flat anterior chamber, or reduced vision should receive prompt treatment. In the absence of complications, the leak may not require therapy, such as in patients who have focal small leaks with formed blebs, normal IOP, good central vision, and no previous episodes of bleb-related infection. Sometimes, an observation period will permit the leak sufficient time to close spontaneously. Treatment with pharmacological agents that decrease aqueous secretion may facilitate this closure by reducing the flow of aqueous through the fistula. Prophylactic broad-spectrum antibiotic coverage that involves alternating different antibiotics is recommended. The prompt diagnosis and management of bleb-related ocular infection depends upon educating patients regarding its symptoms.
Many therapeutic modalities have been proposed to treat late leaks, including lubrication, pressure patching, a bandage contact lens, a glaucoma tamponade shield, a symblepharon ring, the injection of autologous blood cryopexy, thermal Nd:YAG laser, cyanoacrylate glue, and fibrin tissue glue.7 Overall, the long-term success rate of these techniques has been less than 50%, and surgical revision provides a better outcome.9,10
Surgical Techniques for Repair
When treating a late bleb leak, it is important to attempt to save the established, initial filtration site. Due to the conjunctiva's friable nature, it is often impossible to close the defect directly with sutures, so healthy conjunctival tissue is needed. The most commonly used technique consists of placing healthy autologous conjunctiva over the bleb, using either advancement of the conjunctiva (with or without Tenon's layers)11-17 or a free conjunctival autograft.18,19
Conjunctival Advancement
Following this method, the surgeon uses a corneal traction suture (7–0 silk or polyglactin 910) to rotate the globe inferiorly. He then creates a paracentesis, after which he may inject viscoelastic into the anterior chamber. Next, at both sides of the filtering bleb, the surgeon performs a conjunctival peritomy that extends approximately 1 or 2 clock hours at each side. He extends the conjunctival incision surrounding the avascular filtering bleb and dissects the bleb from the healthy, surrounding conjunctiva, which is undermined posteriorly with blunt dissection. A posterior conjunctival relaxing incision may be made at the fornix, parallel to the limbus, creating a pedicle flap to facilitate the advancement of the conjunctiva.20
The surgeon subsequently denudes the ischemic, thin-walled bleb tissue and the limbus of conjunctival and limbal epithelium by blade debridement (No. 67 Beaver blade) and wet-field cautery to allow the long-term adherence of the grafted conjunctiva.17,20 While we prefer this technique, a cellulose sponge lightly soaked in alcohol may also be used to eliminate the epithelium.21 Alternatively, some surgeons excise the whole, thin, avascular bleb wall.12,15,16,22 If there is excessive outflow through the scleral flap, placing additional flap sutures may help. If the scleral flap is too friable to allow suturing, a scleral23,24 or pericardium patch graft20 may be used.
Figure 2. In this revised bleb, healthy conjunctiva and Tenon's has been brought to the limbus. Multiple mattress sutures of 10–0 nylon make the incision watertight.
Next, the surgeon mobilizes the dissected fresh conjunctiva adjacent to the bleb in order to cover it and sutures this conjunctiva over to the previously abraded peripheral cornea. A sclerocorneal groove can facilitate watertight healing. The surgeon may secure the advanced conjunctiva with temporal and nasal mattress sutures (10–0 nylon or 8–0 polyglactin sutures)14 and/or a running suture (10–0 nylon) (Figures 2 and 3). Figure 4 illustrates the different steps involved in conjunctival advancement.
Figure 3. One day postoperatively, the bleb is elevated and without leakage.
Free Autologous Conjunctival Graft
When severe scarring or a large bleb size results in severe tension on the advanced conjunctiva, ptosis and hyperopia may occur. In these cases, bleb revision with a free conjunctival autograft may be a better choice than conjunctival advancement.18,19,25 First, the surgeon should use a caliper to measure the area of the avascular bleb both horizontally and vertically and add 1 to 2 mm in both directions in order to allow for the postoperative shrinkage of the bleb. After rotating the globe superiorly with an inferior corneal traction suture, the surgeon measures the appropriate area of inferior conjunctiva and outlines it with a marking pen. The surgeon then harvests the conjunctiva and sutures the free conjunctival graft into place, covering the avascular bleb, with the limbal edge of the harvested conjunctiva sutured at the limbus with mattress sutures (9–0 nylon, on a BV100 needle [ETHICON, Somerville, NJ]) at the nasal and temporal edges. Finally, the surgeon secures the remainder of the graft with running or interrupted sutures of 9–0 or 10–0 nylon.
Figure 4. The technique of repairing late leaking blebs is demonstrated. The surgeon identifies the leaking bleb with a fluorescein strip (A). After outlining and demarcating the bleb, the surgeon uses Vannas and/or Westcott scissors to cut open the conjunctiva and Tenon's layer while leaving the limbus intact (B). The surgeon widely undermines the conjunctiva and Tenon's layer posterior to and around the bleb so that there is sufficient tissue to bring down to the limbus (C). Next, the surgeon lifts the original edge of the bleb, pulls it toward the limbus, and amputates it there with a Vannas scissors while leaving the scleral bed intact (D). The surgeon brings healthy conjunctiva and Tenon's tissue to the limbus and sews it carefully with 10–0 individual mattress sutures. Alternatively, a running suture may be used (E). If there is too much tension on the conjunctiva/Tenon's flap, a relaxing incision in the fornix may be created. The surgeon may suture the anterior edge with 9–0 VICRYL (ETHICON) (F).
Amniotic membrane transplantation
Amniotic membrane may be used instead of conjunctiva.26,27 A prospective, randomized trial comparing amniotic membrane transplantation with conjunctival advancement reported a better outcome with the latter technique, however.27
RESULTS OF SURGICAL BLEB REVISION
After revision, the bleb is typically thicker with variable vascularization. The IOP is usually the same as preoperative levels or slightly raised, and the patient may need increased medical therapy. Occasionally, some cases may experience a failure of filtration, but the overall success rate of these techniques is approximately 80%.9,10
Marlene R. Moster, MD, is Professor of Clinical Ophthalmology at Thomas Jefferson School of Medicine and Attending Surgeon on the Glaucoma Service, Wills Eye Hospital, Philadelphia. She holds no financial interest in the products mentioned herein. Dr. Moster may be reached at (610) 949-9788; moster@willsglaucoma.org.
Augusto Azuaro-Blanco, MD, PhD, is Consultant Ophthalmic Surgeon and Honorary Clinical Senior Lecturer at the Department of Ophthalmology, Aberdeen Royal Infirmary, University of Aberdeen in Aberdeen, United Kingdom. He holds no financial interest in the products mentioned herein. Dr. Azuaro-Blanco may be reached at +44 12 24 55 32 17; aazblanco@aol.com.
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