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Chicago—Releasable compression sutures can circumvent the limitations of transconjunctival suture lysis and offer several advantages in controlling aqueous flow after trabeculectomy, according to Murray A. Johnstone, MD, a consultant in glaucoma at Swedish Medical Center, Seattle.
Dr. Johnstone described his suture technique in a presentation at the American Academy of Ophthalmology meeting during the glaucoma specialty day program.
With releasable compression sutures, "we have suture control of trabeculectomy flow, which provides a self-adjusting mechanism to control IOP, maintains chamber depth, prevents early flat chambers, avoids posterior segment issues, and generally assures a benign postoperative course," he explained.
"Clearly the use of releasable or some sort of adjustable suture is important. Laser suture lysis can be an excellent tool. It provides the ability to use tighter sutures with the knowledge that they can be predictably released. However, there are certain limitations, including pain from lens placement, trauma to the flap, and access problems, especially in those cases where you most need it, including those with thick Tenon's tissue or blood," Dr. Johnstone said. "There is a risk of perforation, especially in the presence of blood, and in cases with mitomycin-C, chronic wound leaks."
Convenience is another issue because use of sutures may involve scheduling patients with an off-site laser provider or moving them back and forth to a laser room within the office for suture release.
Modified suture techniques
To get around these obstacles, surgeons have developed or modified other techniques, such as interrupted releasable sutures that are then externalized, making them easily removable. Externalized sutures can always be removed, even in the presence of thickened, edematous, or hemorrhagic conjunctiva. Flap perforation is avoided, and pain and flap disruption associated with lens placement are also avoided.
These techniques with interrupted sutures, however, have relatively high rates of chamber shallowing, leading clinicians to search for additional solutions.
The reported incidence of postoperative chamber shallowing is 71% with full-thickness procedures and 33% to 54% with trabeculectomy. With releasable sutures, a 14% incidence rate has been reported. In such cases, the physicians tie the sutures tightly with the knowledge that they could release them if they need to, Dr. Johnstone said.
His contribution is a self-adjusting compression suture that he has used in about 4,000 cases. In published reports of his experiences with the self-adjusting compression suture, Dr. Johnstone noted a 3% incidence of chamber shallowing as determined by objective measurements of chamber depth.
In this technique, the surgeon places an X or compression suture over the scleral flap. "They are long elastic sutures, so if the pressure is low, the flap is held down and no fluid flows. If the pressure rises, the flap can distend with elastic sutures, and fluid can flow out of it," Dr. Johnstone said.
The technique involves using a double-armed, 10-0 nylon suture passed beneath the conjunctival reflection on both sides of the scleral flap. The suture is laid aside, and a second suture is placed at the posterior edge of the scleral flap and tied loosely with a knot beneath the flap. The suture is tied in such a way that the flap will lift about 15°.
Next, the left arm of the initial suture is passed through the posterior arm of the scleral-flap suture. By pulling forward, it is possible to compress the posterior portion of the scleral flap along its entire length.