How is the scleral flap closed during trabeculectomy?

Updated: May 18, 2020
  • Author: Maria Hannah Pia Uyloan de Guzman, MD; Chief Editor: Hampton Roy, Sr, MD  more...
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Scleral flap closure

The scleral flap is closed using simple interrupted, releasable, or adjustable 10-0 nylon sutures, or a combination of these. The sutures are placed at the flap edges taking care to avoid puncturing the part of the flap overlying the sclerostomy. Areas where the flap is too thin should also be avoided. The suture knots should be buried to avoid the suture "whiskers" from poking through the bleb.

Various releasable [18, 19, 20, 21] and adjustable [22, 23] suture techniques have been described. Both releasable and adjustable sutures are more difficult to place than simple interrupted sutures. Releasable sutures allow the surgeon to remove sutures at the slit lamp without the need for an argon laser (laser suture lysis). This is used to lower the postoperative IOP if it is higher than desired. Adjustable sutures, on the other hand, allow the loosening (or even tightening [23] ) of the suture to titrate the flow through the flap. See the images below.

A commonly used releasable suture technique. A commonly used releasable suture technique.
Left eye 2 weeks after surgery. A releasable sutur Left eye 2 weeks after surgery. A releasable suture at the superonasal corner of the scleral flap is visible beneath the conjunctiva. The releasable suture at the superotemporal corner had been removed previously. There is a releasable suture (blue) at the superonasal corner of the scleral flap. The flap is outlined in green. The simple interrupted scleral flap sutures and conjunctival anchoring sutures are in black.
Left eye immediately after removal of a releasable Left eye immediately after removal of a releasable suture. The flap outline and the simple interrupted flap sutures are no longer visible due to the increased bleb elevation.

After the first few flap sutures have been placed, the aqueous flow through the flap is assessed. First, the AC is reformed by injecting fluid through the paracentesis track. Then, using a small sponge, the flap edges are dried and the amount of aqueous leakage and the stability of the AC are observed. If the AC shallows quickly or there is excessive flow of aqueous, sutures can be added or loose ones replaced. If there is no flow through the flap, the AC will remain formed and the globe may be tense. In this case, the existing sutures can be loosened by gently stretching them or tight sutures replaced with looser ones.

An indication of the ideal flow rate is when it takes several seconds for the bottom of the gutter around the flap edges to fill with fluid. However, the flow rate endpoint depends on the target postoperative IOP and the surgeon's preference. It is better to err on the side of too little flow because there are many effective and noninvasive remedies for postoperative high IOP (eg, IOP-lowering medication, laser suture lysis, releasable sutures, release of fluid through the paracentesis track) but there are hardly any for excessively low postoperative IOP.

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