Simulated Surgery: Trabeculectomy: Suturing a Scleral Flap

The SOS Advanced Trabeculectomy eye is being used to demonstrate how to place releasable scleral flap sutures using 10/0 nylon sutures and how to tension these sutures to minimize drainage on the first post-operative day to avoid hypotony. Simultaneous live and simulated surgical footage demonstrates how realistic this simulation is.

In addition to Cybersight, you can find videos featuring teaching techniques for all types of ocular surgery, using any form of simulation, in the Simulation Gallery.


The next stage of the operation is suturing of the scleral flap. We use 10-0 nylon for this part of the operation, and the synthetic surgery eye is ideal for practicing suturing skills with this demanding material. I prefer to place a fixed 10-0 nylon suture in each corner of the scleral flap. As this allows the trainee who is learning to pass releasable sutures safe time in which to develop this technique. It reduces the time that the eye is hypotonous, as placing the releasable suture can sometimes be a little time-consuming. So I cut the fixed suture long, because it’s going to be later removed. So placing the fixed suture at the other corner of the scleral flap. We do put water on the surface of the simulated surgery eye. As this makes handling the 10-0 nylon somewhat easier. And again, it’s more like the natural situation, when operating on the patient’s eyes. As this second suture is tied, the eye can be reestablished with saline injected through the paracentesis, to normalize the pressure during the process of placing the more time-consuming releasable sutures. The first step of the releasable suture is to pass the needle backhand towards the limbus, with the needle exiting through the corneal groove that’s been placed previously. The needle is then regripped and passed in the conventional direction, finally emerging through the scleral flap about 2/3 along its length. The needle is then re-passed through the corner of the scleral flap, underneath and emerging just beyond the end of the fixed suture. Being careful not to perforate conjunctiva. At this point, the fixed suture can be safely removed, and the releasable suture can be completed. The suture’s pulled through, leaving a small loop protruding from the scleral flap. And then the suture is tied back onto that loop, using three turns. The precise technique used for the releasable suture is at the surgeon’s discretion. For example, some surgeons use four turns on their releasable sutures, as it provides a more secure grip and a lower likelihood that the suture can be loosened if the patient rubs their eye. So placing the second releasable suture, starting with a backhand pass of the needle, pulling the thread through. Regripping the suture. And then passing it through and along the scleral flap. Reemerging about two thirds of the way along the flap. Pulling the suture through again. And passing the suture under the fixed suture. Particularly important as the suture reemerges not to buttonhole the conjunctiva. At this point, the fixed suture can be cut. And removed. The releasable suture is then tied with three turns, back onto the loop. The eye is now reestablished with injection of BSS through the paracentesis into the anterior chamber, and the tension of the releasable sutures can then be checked to ensure the high pressure within the eye. When the tension in the releasable sutures is considered satisfactory, the sutures can then be trimmed short. It’s quite important not to have long ends protruding, because postoperatively, with a thin trabeculectomy, these can sometimes protrude. So I cut them short. You can see the two releasable sutures in situ, at each corner of the scleral trapdoor.
Last Updated: October 31, 2022

1 thought on “Simulated Surgery: Trabeculectomy: Suturing a Scleral Flap”

Leave a Comment