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Scleral flap elevation

Scleral flap elevation by filtration enhancing knot in trabeculectomy.

The basic problem in trabeculectomy operation or any filtration operation is that filtration is maximum on day one and gradually wound heals up and filtration becomes less. At this time our expectations are that we should achieve target pressure. Naturally we want to keep iop below target pressure for first few days. So that even if wound heals and filtration becomes less we get appropriate target pressure on long term. But in getting this sometime we land up in a problem of flat anterior chamber and its consequences.

To avoid this it would be better if we aim at iop slightly higher than target pressure for first few days and then reduce it as per our requirement by enhancing filtration. But, how to do this? For this we have come out with this new technique.

To overcome this problem of flat AC, filtration-enhancing knot can be of great help. We can keep IOP above target pressure in the initial post operative period & filtration can be enhanced thereafter as per requirement, simply by elevating scleral flap, holding the filtration enhancing knot. As the IOP is above target pressure on day one without any hesitation patient can be discharged on same day. Secondly if IOP pressure is maintained for first few days and then after seven days if pressure is reduced to great extent like 4 mm of hg then cornea is sucked in rather than iris lens diaphragm being pushed forward. This happens because once the anatomy is restored and maintained then even if IOP falls to zero probability of flat anterior chamber is less. We will get sucking of cornea in. But the iris lens diaphragm is not pushed forward.


Limbal based conjunctival flap is made (fig.1). Then routine trabeculectomy surgery is done. After excising the deep scleral flap and before suturing superficial scleral flap, take 8-0 nylon suture. This is passed through conjunctiva one mm away from limbus & in the region of center of superficial scleral flap, then through tenons, then partial thickness of scleral flap & out through tenons & conjunctiva (fig.2). A loose knot is tied on conjunctiva fig.3. This I call it as filtration enhancing knot. Then trabeculectomy wound closure is done in usual fashion fig.4 aiming postoperative pressure slightly higher than the target pressure. After 4 days the IOP is measured. If bleb is small then filtration-enhancing knot is pulled up. This elevates the scleral flap & conjunctiva, which will cause aqueous to leak below conjunctiva & will be visible as bleb. This should be done under topical anesthesia on slit lamp or operating microscope. Every fourth day patient is called till the IOP is below target pressure & bleb is good for consecutive three visits. If it is not, then by pulling the filtration enhancing knot bleb can be increased. Suturolysis or digital massage can be combined if necessary. Usually the suture taken through superficial scleral flap (8 zero nylon of filtration enhancing knot) is removed after one month.

Area of added attention and possible problems

Filtration enhancing knot suture should pass through tenons. It may cause foreign body sensation. Pulling may cause small hemorrhage. Rarely leak may be there from the suture area. This can be prevented if needle passes through tenons and partial thickness of sclera.