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Steps for saving failing blebs after trabeculectomy
Needling can be successful in early and late cases of bleb revision.
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The most common cause of glaucoma surgery failure is subconjunctival fibrosis in the bleb. The rapid wound-healing response can present in one of two ways:
- Sub-conjunctival fibrosis leads to lack of filtration and a flat bleb with subsequent increases in IOP. This can occur at any stage after the operation and is the most common cause for failure after trabeculectomy, both in the early and late postoperative periods. The incidence of failure from subconjunctival fibrosis is approximately 20% in the early period and 30% to 50% in the late postoperative period.
- Sub-Tenon’s encapsulation of blebs presents as raised, often angry-looking blebs with elevated IOP. This usually occurs in the first 1 to 6 months after surgery and is seen in 10% to 20% of patients after trabeculectomy.
In an attempt to control the fibrotic response, anti-inflammatory agents, such as steroids, and antimetabolites, such as mitomycin-C (MMC) and 5-fluorouracil (5-FU), have been used. They have increased the success rate of trabeculectomy operations to 80% to 85% at 1 year. Five-year success rates are still around 50% to 60% despite the use of antimetabolites. Thus, increasing IOP with failing blebs is an issue after any kind of glaucoma surgery. Herein we present our techniques in saving failing blebs after trabeculectomy.
Preoperative measures
Some patients develop chronic allergic reaction and conjunctival inflammation from topical glaucoma medications. Conjunctival inflammation must be treated before subjecting patients to glaucoma surgery. Discontinuation of the offending medication, substituting topical medications with oral acetazolamide and low-dose topical steroids for a 2-week period before surgery help to reduce conjunctival inflammation.
Some people develop conjunctival inflammation because of other reasons, such as lid-margin inflammation and ocular rosacea. This should also be addressed before surgery. Simple measures such as lid hygiene, application of TobraDex ointment (tobramycin dexamethasone, Alcon) at bedtime to the lid margins and conjunctiva, and oral tetracycline for a 3- to 4-week period before surgery help to enhance the success rate of surgery. In patients who require surgery immediately, these measures can be continued in the postoperative period.
Intraoperative measures
Intraoperative manipulation of the conjunctiva or Tenon’s capsule during surgery should be decreased. It also helps to minimize intraoperative bleeding.
Sub-Tenon’s injection of 1% preservative-free lidocaine after peritomy will not only facilitate local anesthesia, but it is also a nontraumatic way of conjunctival dissection.
Use of intraoperative antifibrotic agents such as MMC or 5-FU can be helpful, as is placement of the antifibrotic agents under the scleral flap and in the posterior subconjunctival space.
Postoperative measures
Postoperative steroids can be used for 6 to 8 weeks after surgery. It is helpful to slowly taper off the steroids.
Subconjunctival injections of 5-FU can be used in patients with angry-looking blebs in the immediate postoperative period. Digital massage can be instituted early on in case of a low bleb.
Some patients can develop a persistent leak in the early postoperative period that results in a low bleb. By the time the leak heals and the bleb becomes Seidel’s negative, the rest of the bleb can scar down, leading to a sudden increase in IOP. In these patients, it may be wise to seal the leak with a 10-0 Vicryl suture at the slit lamp in an attempt to elevate the bleb and prevent it from scarring down.
(All photos are courtesy of Analisa Arosemena, MD, and Ramesh S. Ayyala, MD, FRCS, FRCOphth.) | |
Elevated IOP
Low bleb with absent conjunctival microcysts is associated with an elevated IOP. This can happen in the early or late postoperative phase after trabeculectomy. Low blebs in the early postoperative period can occur because of subconjunctival fibrosis alone, or they can be secondary to an obstruction of the aqueous pathway, such as a blood clot, multiple tight sutures closing the scleral flap or the iris plugging the sclerostomy.
A blood clot in the sclerostomy site usually resolves spontaneously over a 48- to 72-hour period. If not, the clot can be dissolved with an intracameral injection of 0.6 µm to 1.2 µm of tPA.
Some surgeons believe in closing the scleral flap with multiple sutures to avoid immediate postoperative hypotony and flat anterior chambers. This technique will result in the formation of a flat bleb in the early postoperative period. Suturelysis is indicated in these cases to increase the aqueous outflow.
Peripheral iridectomy at the time of the surgery usually prevents the iris from plugging the sclerostomy site. In cases where a peripheral iridectomy is not performed, the iris may plug the sclerostomy site, leading to an acute elevation in IOP (greater than 30 mm Hg). This can happen either spontaneously or after digital massage. In either case, the patency of the sclerostomy site may be re-established. This can be done in one of several ways.
- Use of miotics such as Pilocarpine (pilocarpine HCI ophthalmic solution USP, Bausch & Lomb); however, this rarely works.
- Iridectomy with Nd:YAG laser using the goniolens. This can open the sclerostomy but may result in a lot of inflammation secondary to the pigment released.
- Sweeping the iris away from the sclerostomy site followed by the use of miotics. This can be done at the slit lamp. The eye is prepped with Betadine (povidone iodine, Alcon) and anesthetized with topical tetracaine drops. A lid speculum is inserted, and the patient is positioned at the slit lamp. The procedure is performed with low or medium magnification so that the entire eye is always in the field of view. Paracentesis is performed with a sharp blade in the temporal quadrant. The anterior chamber is injected with 0.1 cc of a low molecular weight viscoelastic. The viscoelastic cannula is then used to sweep the iris away from the sclerostomy site.
The sooner the iris is swept away from the sclerostomy site, the easier the procedure. If you wait, the procedure will be more difficult. Also, the procedure may be associated with bleeding, and hyphema and inflammation can be expected. This procedure is associated with some degree of pain, and the patient should be warned about this. Postoperatively, the patient should be treated with miotics, antibiotics and anti-inflammatory drops. In our experience, this procedure is more likely to achieve results with minimal inflammation compared with the YAG laser.
If these measures fail, topical glaucoma medications should be reinstated. If the target IOP is not achieved on topical drops, then the patient may need more surgery, either another trabeculectomy or implantation of a glaucoma drainage device.
Aggressive treatment
Once recognized, a failing bleb should be treated aggressively, especially in the early postoperative period. The treatment includes vigorous digital massage, aqueous suppressants and needling with 5-FU injection. Bleb revision with the needling technique can be successful in early and late cases.
Early bleb failure occurs within the first 3 months after trabeculectomy. It can be secondary to rapid healing response or bleb encapsulation. In either case, needling the bleb followed by digital massage and 5-FU injections might revive the filtration. The success rate of needling in early cases is approximately 30% to 40%.
In our practice, when a patient is referred for management of glaucoma and he had a trabeculectomy operation several years earlier that failed, the first thing we do is try to revive the old trabeculectomy site with needling. In approximately 40% of patients, the bleb can be revived and IOP can be controlled to the target range. It is important to note that the success of this procedure depends on the early institution of digital massage. We encourage patients to perform digital massage six to eight times per day starting 4 to 6 days after the needling procedure. If these measures fail, then surgical revision or repeating the glaucoma surgery in a virgin area should be considered.
Bleb revision with needling
Needling of the bleb is performed in the outpatient clinic. After instillation of topical anesthetic and antibiotic drops, a cotton tip applicator soaked in topical anesthetic is applied for 2 minutes to the conjunctival site where the needle will enter. A lid speculum is placed in the eye. At the slit lamp, the patient is instructed to look down so all of the bleb is exposed.
The site of the trabeculectomy operation should be identified. Sometimes, in patients who had the surgery several years earlier, it may be difficult to identify the scleral flap site. Gonioscopy will help in identifying the site of sclerostomy and the iridectomy. This should give the surgeon an idea of the probable site of the scleral flap. The slit lamp is set at the lowest magnification. This facilitates visualization of the bleb even if the patient moves his eye during the procedure.
Needling is performed with a 27-gauge needle on a tuberculin syringe. The needle is introduced into the subconjunctival space, 1 mm from the edge of the bleb, and advanced into the bleb. The subconjunctival fibrosis is cut with a firm back-and-forth motion. The needle is then advanced in the same plane into the other side of the scleral flap, and the fibrous tissue is cut. The needle is then partially withdrawn from the bleb and the direction changed to parallel the edge of the bleb; with sweeping motions, the scar tissue is cut. The idea is to cut the fibrous tissue in all directions around the scleral flap. The needle is then withdrawn.
It is important to identify the scleral flap area because in most cases the subconjunctival fibrosis extends all the way to the junction of the scleral flap edge. If the subconjunctival fibrosis is dissected to the edge of the flap, aqueous will start to leak, forming a nice bleb. In some cases, the fibrosis extends under the scleral flap. In these patients, an attempt has to be made to lift the edge of the scleral flap. The needle is then passed under the flap. If aqueous does not present into the subconjunctival space, then the dissection can be carried further with the needle entering the anterior chamber via the sclerostomy site. This maneuver should be attempted only in the most cooperative patients where the scleral flap can be clearly identified.
Frequently, a change in the appearance of the bleb is seen during or soon after needling with the size increasing and the bleb becoming less tense. We routinely give 5-FU injections (5 mg in 0.1 cc) into the subconjunctival space in the inferior fornix, away from the bleb. Slit lamp examination with Seidel test is performed 30 to 60 minutes later. Patients are instructed to use topical antibiotics with steroid drops for 5 days and start gentle digital massage from day 3; they are usually seen again in 3 to 5 days. It is critical for digital massage to be instituted early and continued into the long term because it keeps these blebs functioning.
Complications of bleb needling
Complications include bleb leaks, choroidal effusions, suprachoroidal hemorrhage and endophthalmitis. Bleb leaks can be sealed with 10-0 Vicryl on a BV needle. Choroidal effusions usually resolve with topical cycloplegics and topical or systemic steroids. Preventive measures, such as prepping the eye, placement of Betadine into the conjunctival sac before the procedure and postoperative antibiotics, reduce the risk of endophthalmitis.
We had two patients who developed suprachoroidal hemorrhages after needling over the past 4 years. Both patients were on anticoagulants and had trabeculectomies done 5 to 8 years before referral. They both had uncontrolled IOP with advanced glaucoma. Needling successfully revived the blebs and lowered IOP to the target range. The patients had delayed peripheral suprachoroidal hemorrhage 12 hours after the needling episode. They were both successfully treated with pain medications, topical cycloplegics and topical systemic steroids. The suprachoroidal hemorrhages resolved over a 3-week period.
For Your Information:
- Analisa Arosemena, MD, and Ramesh S. Ayyala, MD, FRCS, FRCOphth, can be reached at Glaucoma Service, Department of Ophthalmology, Tulane University Medical Center, 1430 Tulane Ave., SL-69, New Orleans, LA 70112; 504-584-2466; fax: 504-584-2684; e-mail: rayyala@tulane.edu. Drs. Ayyala and Arosemena have no direct financial interest in the products mentioned in this article, nor are they paid consultants for any companies mentioned.