Answer
Conjunctival closure
When there is a satisfactory amount of aqueous flow through the flap and the flap suture knots are buried, conjunctival closure can begin. As is the case during the initial dissection of the conjunctiva, the conjunctiva should be handled gently and only Tenon capsule grasped whenever possible.
Nylon 10-0 sutures with a round (vascular) needle are preferred. Absorbable sutures can be used but they may induce conjunctival inflammation. Spatulated (side-cutting) needles can also be used when suturing the conjunctiva to the limbus (fornix-based flap). However, using a spatulated needle to suture conjunctiva is more likely to cause a conjunctival buttonhole or tear than a round needle.
Limbus-based conjunctival flaps can be sutured using a simple running or an interlocked running suture. It can be closed in layers or the Tenon capsule and conjunctiva can be closed together. There should be no tags of Tenon capsule protruding from the wound as these could cause leakage or fistula formation.
Fornix-based conjunctival flaps are more difficult to close. The closure can be conjunctiva-to-cornea if the conjunctiva was cut flush with the limbus or conjunctiva-to-conjunctiva if a narrow skirt of conjunctiva was left attached to the limbus. First, the rolled up edges of the distal conjunctiva are gently unrolled. For conjunctiva-to-cornea closure, the conjunctiva is then stretched to slightly beyond its original insertion. Simple interrupted or purse-string sutures are used to anchor the nasal and temporal edges of the conjunctiva to slightly beyond their original position (called the "wing sutures"). The conjunctiva becomes stretched between the nasal and temporal wing sutures and this is confirmed if an indented line is seen running from the nasal to the temporal wing sutures. The conjunctiva should be watertight at this point, leaking only when pressure is applied to the bleb. See the image below.
In a fornix-based flap, after the 2 wing sutures have been placed, a tension line (blue dashed line) may be seen running between the 2 sutures. This is a good indicator that the wound is already watertight. This is also a good reference point for the placement of the limbal mattress sutures.
For added safety, a few mattress sutures can be used to anchor the conjunctiva parallel to the limbus along the indented line created by the placement of the wing sutures. All sutures should be placed or tied in such a way that the knots are buried beneath the conjunctiva or within the limbal tissue. If burying the knots is not possible, the suture ends can be left slightly long to reduce the foreign body sensation that would be caused by protruding short suture whiskers.
For conjunctiva-to-conjunctiva closure, the conjunctival edges are apposed using a running suture or a few mattress sutures.
If aqueous was flowing through the scleral flap, a bleb would have formed during the closure of the conjunctiva. The bleb can be pressed gently using a sponge and the wound observed for leakage. Sterile fluorescein dye can be used as an adjunct for this step. If the scleral flap was closed tightly, a bleb can be induced by indenting the sclera beside the flap.
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Photograph showing an eye after trabeculectomy. The peripheral iridectomy is ideal in its shape, size, and location.
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Corkscrew vessels in a bleb 1 week after trabeculectomy.
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A conjunctival bleb a few days after trabeculectomy. The bleb is of an ideal height and is diffusely elevated. Although it has slightly dilated blood vessels, they are not excessively tortuous. The limbal sutures should have been buried or tucked under the conjunctiva.
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Flow of aqueous after a trabeculectomy.
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The ideal flap size in relation to the sclerostomy. The distance between the flap edge and the sclerostomy edge should be greater than or equal to the width of the sclerostomy.
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Diagram showing the ideal extent of internal dissection under the scleral flap and the ideal extent of the flap sides (external).
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The paracentesis should be placed at an easily accessible point and should be directed away from the lens as in this example of a right eye.
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As the scleral flap dissection approaches the limbus, the blade should be angled more parallel to the corneal curvature (green dashed line arrow) to avoid premature entry or entry into the anterior chamber that is too close to the iris plane (red dashed line arrow).
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The peripheral iridectomy should have a broad base that is wider than the sclerostomy.
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In a fornix-based flap, after the 2 wing sutures have been placed, a tension line (blue dashed line) may be seen running between the 2 sutures. This is a good indicator that the wound is already watertight. This is also a good reference point for the placement of the limbal mattress sutures.
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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.
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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.
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At the anterior limit of the scleral flap the blade is redirected parallel to or towards the iris (green dashed line arrows, left). The "sclerostomy" is actually corneal tissue anterior to the trabecular meshwork/Schlemm canal (right).
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A commonly used releasable suture technique.
