New technique addresses high-risk filtering procedures

Limbus-based conjunctival scleral trabeculectomy flap bypasses the episcleral scar and leaves the conjunctiva undisturbed.

In our previous article, we presented a trabeculectomy technique that utilized a posterior limbal conjunctival flap to prevent scarring in the filtering area (See “New approach to trabeculectomy preserves episcleral tissue” in the May 25, 2008, issue of Ocular Surgery News on page 21).

As a follow-up to that article, we now address the issue of performing successful trabeculectomy in the presence of pre-existing episcleral scarring resulting from a previous surgery or trauma.

The current methodology for performing trabeculectomy under these conditions entails the excision of the episcleral scar and conjunctival tissue, the creation of a fornix-based flap to cover the filtering area, and the use of mitomycin to prevent recurrence of scarring.

Despite improved results, a major drawback of this approach is that by excising the scar, we risk new trauma to the filtering area and often end up replacing the old scar with a new one.

In order to dramatically reduce this risk, here we present a new technique that uses a conjunctival scleral limbus-based flap to bypass the episcleral scar. Using this approach leaves the conjunctiva undisturbed and reduces scarring to the filtering area while still allowing for successful trabeculectomy.

In effect, using this procedure presents a major paradigm shift away from viewing the scar as an obstacle that must be removed at all costs to a viewpoint in which we work with the scar to achieve our objectives.

Technique

After initial anesthesia, a balanced salt solution is injected under the Tenon’s space to delineate the scarring. A conjunctival flap 8 mm from the limbus and 5 mm wide is created to expose the sclera to the edge of the episcleral scarring.

Conjunctival scleral-based flap is created 8 mm from limbus.

Deep scleral trabeculectomy flap is created. Images: Khaliq A

Internal ostium is created with Kelly’s punch.

Trabeculectomy flap closed with three 10-0 nylon sutures.

Conjunctival wound is closed.

A 3-mm wide incision is made with a crescent knife at the edge of the scarring to engage the very superficial fibers of the sclera. The plane of dissection is then carefully extended sideways along the nasal and temporal edge of the scar and anteriorly toward the limbus to create a limbus-based flap. Mitomycin is applied to the scleral bed for 4 minutes, and a deep trabeculectomy flap measuring 3 mm by 3 mm is created with its base at the limbus.

A paracentesis is created at 2 o’clock, and the anterior chamber is filled with viscoelastic. The anterior chamber is entered with a 3-mm keratome, and trabeculectomy is performed using a Kelly punch. A peripheral iridectomy is performed, and the trabeculectomy flap is repositioned by suturing with three 10-0 nylon sutures. The conjunctival scleral flap is also repositioned, and the wound is closed with 10-0 nylon running sutures.

Conclusion

In addition to reducing scarring to the filtering area, this technique also has some added benefits.

Because the conjunctival scleral flap is rigid and limbus-based, it stays away from the filtering area and does not lie flat. We curtail further scarring over the trabeculectomy area and experience fewer wound leaks using this procedure.

Although only a small number of cases over the past 3 years have been performed using this technique, the results look promising.

• Abdul Khaliq, MD, FRCS, can be reached at Northern CT Eye Associates, 146 Hazard Ave., Suite 106, Enfield, CT 06082; 860-763-4046; fax: 860-763-3856; e-mail: khaliq42@hotmail.com.