What to do when blebs start to fail

Take-home:

Bleb failure can often be avoided with well-managed trabeculectomy and effective postoperative care.

By Nancy Groves; Reviewed by Keith R. Martin, MD, FRCOphth

Cambridge, England-When blebs start to fail, clinicians need a systematic approach, and the first principle is that prevention is better than cure.

Intervention sooner rather than later is also better, said Keith R. Martin, MD, FRCOphth, professor of ophthalmology, University of Cambridge, Cambridge, England.

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Steps most likely to avoid failure, he said, are:

• careful trabeculectomy,

• meticulous technique,

• watertight closure of the limbus,

• control of scarring, and

• attentive management of postoperative inflammation.

The first days and weeks following surgery are a critical period, Dr. Martin said.

“During this time, adjustment or lasering or removal of flap sutures can be effective,” he said. “Bleb massage can be useful in some of our patients, although it’s important to recognize that this is not a substitute for control of the inflammation by other methods.

The next management principle is to identify the site of failure.

“If your bleb is flat, it’s likely that you have either obstruction of the internal ostium, scarring of the flap, or a leak,” Dr. Martin said. “Gonioscopy is key here in the assessment, and it’s often neglected. With gonioscopy, you can see directly if the internal ostium is obstructed or if there’s no visible sclerostomy, in which case needling is very likely to be unhelpful.”

Once the site of failure has been found, intervention can be planned. While needling can often be performed safely in an office or clinic, it is worth considering whether it would be preferable to use an operating room. This may be a wise choice if it is likely that the needle will be inserted underneath the flap into the anterior chamber or if previous needlings have been difficult or have failed.

It is also necessary to plan the anti-scarring treatment. Options include mitomycin or 5-fluorouracil (5-FU), although there is evidence that anti-vascular endothelial growth factor agents may be effective, Dr. Martin said.

5-FU is still widely used and may be combined with viscoelastic, which is useful for separating the tissue planes both at the time of needling and postoperatively. It also aids slow release of the drug and helps reduce corneal toxicity by limiting the efflux of 5-FU after the needling,

“We’re also increasingly using topical mitomycin, and there’s good evidence that by topical application we can reach therapeutic concentrations at the level of Tenon’s capsule, and it’s safe when used at low concentrations,” Dr. Martin explained.

His needling technique includes using apraclonidine 1% preoperatively, about 15 minutes before the procedure. This helps to vasoconstrict and reduce the risk of bleeding. Dr. Martin prefers to use a bent 30-gauge needle with viscoelastic, although a larger needle may be helpful in cases with more scarring. He also uses a lid speculum for most cases.

If the bleb has formed, then subconjunctival needling may be all that is required.

However, a flat bleb may require elevation of the scleral flap and entry into the anterior chamber via a sclerotomy to establish flow. An anterior chamber maintainer providing positive pressure infusion can be very useful in these cases, helping establish good flow.

It is also possible to set the opening pressure and gauge the resistance by adjusting the bottle height, Dr. Martin said.

He also offered tips for managing difficult cases. If the patient is unable to look down, a corneal traction suture may help in gaining access behind the flap. Anterior chamber infusion using a Lewicky 23- or 25-gauge cannula and 3-way tap gives the surgeon a greater degree of control over the procedure.

Viscoelastic is also useful in challenging cases, Dr. Martin said.

He added that it is often difficult to avoid making a hole in the conjunctiva, particularly when scarring is present.

“If this occurs very close to the flap, it’s worth considering repairing these holes because if you don’t you’re very likely to end up with a flat bleb post-procedure,” he said. “If you do repair these you can then proceed and complete the viscodisscetion and separate the planes more effectively.”

Finally, Dr. Martin urged his colleagues to assess cases carefully before intervening.

“You’ve got to realize whether or not you’re likely to achieve your target pressure in the long term,” he said. “Repeated needlings over and over again are often futile. We frequently need to move on to consider alternative medical or surgical approaches.”

Keith R. Martin, MD, FRCOphth

E: kmartin1@doctors.org.uk

This article was adapted from Dr. Martin’s presentation during Glaucoma Subspecialty Day presentation at the 2014 meeting of the American Academy of Ophthalmology. Dr. Martin is a consultant and lecturer for Allergan.