Box 7.1: Trabeculectomy
1.Superior limbus, under the lid, is the only acceptable site (document lid position preoperatively).
2.Place a 7/0 corneal traction suture (semicircular needle).
3.Use spring scissors to make a limbal conjunctival incision (‘fornix-based flap’), at least 10 mm long.
4.Posteriorly, dissect a 15 × 15 mm subconjunctival pocket.
5.Lift conjunctiva and separate its attachments to muscle tendon.
6.Create a 4 × 3 mm scleral pocket by lamellar dissection (50% thickness) (Fig. 7.7).
7. Cut side incisions to within 1 mm of the limbus (Fig. 7.8).
8.Soak 4–6 sponges with mitomicin C (0.2 or 0.5 mg/mL) or 5FU (50 mg/mL) if required.
9.Fold and insert sponges into the subconjunctival and scleral pockets. Treat as large an area as possible but avoid the conjunctival wound edges (Fig. 7.9). After 3 minutes remove sponges and irrigate with 20 mL of balanced saline solution (BSS).
10.Preplace 10/0 Nylon sutures on the posterior corners of the scleral flap.
11.Make an oblique paracentesis. Consider continuous anterior chamber infusion in ‘high-risk’ patients.
12.Create a small (1 mm) limbal keratectomy with punch, or blade and scissors under the scleral flap (Fig. 7.10).
13.Create a peripheral iridectomy.
14.Suture the flap watertight with a combination of permanent, releasable or adjustable sutures (especially important with MMC use) (Fig. 7.11).
15.Test outflow by injecting BSS into the paracentesis, before conjunctival closure. Rotate any ‘permanent’ scleral flap sutures.
16.Close conjunctiva with 10/0 Vicryl purse-string sutures at the corners, and mattress sutures through conjunctiva and limbus.
17.Inject subconjunctival steroid and antibiotic, 180º away from the trabeculectomy site.
18.Ensure careful postoperative management. (see p. 294)
