Simulated Surgery: Trabeculectomy: Creating a Scleral Flap

The SOS Advanced Trabeculectomy eye can be used to simulate all of the steps of a trabeculectomy. This video demonstrates how to dissect the conjunctiva, create a scleral flap, perform a sclerostomy and peripheral iridectomy. Twin screen footage of simulated and live surgery being performed simultaneously illustrates how realistic the 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.


>> This is one of three videos produced by Andy McNaught, which has spliced together videos of simulated trabeculectomy surgery on the SOS model eyes and live surgery, to illustrate his preferred trabeculectomy technique.

>> We use the basic glaucoma eye for practicing the various stages of the trabeculectomy. The first stage is placing a corneal traction suture. The suture is passed through the peripheral cornea. Vicryl suture. Which is then pulled down under gentle tension, and then taped to the patient’s cheek, to ensure that the eye is in the optimal position for the various stages of the trabeculectomy operation. You can see in the simulated eye that we’ve taped this to the model eye head, thereby exposing the superior fornix ideally, to allow trabeculectomy surgery. The simulated eye has a layer of plastic conjunctiva, which has a very natural feel. You can see the incision is made close to the limbus. And then the Westcott scissors are used to spread underneath the simulated conjunctiva to create a pouch, which will form the trabeculectomy bleb. Note the gentle handling of the conjunctiva and the spreading action of the Westcott scissors, with no cutting, except to enlarge the wound, which needs to be of sufficient width to allow the rest of the trabeculectomy to proceed. Next, a sponge soaked in mitomycin is carefully placed in the conjunctival pouch, being careful to avoid touching the mitomycin onto the edges of the conjunctiva, and left for a variable period of time. Perhaps a minute. Then retrieved. Again, careful not to allow the mitomycin to touch the conjunctival edges. And then ample irrigation to remove the mitomycin. Corneal traction suture, placing two shallow incisions in the peripheral cornea, for burying the releasable suture loops. Next, using the diamond knife, I’m making a partial thickness scleral incision to allow the scleral flap to be formed. You can see the depth of the incision there. With the ideally designed crescent blade, and inserting this into the scleral incision, I’m able to start the formation of the scleral flap, advancing towards the limbus. This is a very important part of the operation, as it’s crucial that the scleral flap is not too thin or too thick, which would risk entering the anterior chamber too posteriorly. The simulated surgery eye has a very natural feel, and the process of forming a scleral flap feels very realistic to the trainee. The next stage is transforming the dissection I’ve undertaken with the crescent blade into the flap itself, gently lifting the posterior margin of what’s to be the scleral flap. I upcut along the edge of the pouch that I’ve formed with the diamond knife, advancing towards the limbus. Again, the anatomy of the simulated surgery eye is very realistic, so having done one side, I gently lift up the posterior margin of the flap and open the other side to form a trapdoor. Ready for the next stage of the operation. I’m using plain non-toothed forceps at this point, because I’ve found that the toothed forceps were more likely to damage the flap when it was being formed, although the flap is slippery. This is another operation on a different simulated surgery eye, which will demonstrate the same stage of the operation. I’ve made an incision in the sclera, and using the crescent blade again, I’m forming a pouch in the sclera, advancing towards the limbus. Which will ultimately form the trabeculectomy scleral trapdoor. You can see that the traction suture provides a non-traumatic way to position the eye and steady it during the dissection. The simulated surgery eye provides a very natural and surprisingly realistic feel during this part of the operation. Again, upcutting along the edge of the scleral pouch to form the scleral trapdoor. And opening up the other side of the scleral pouch by upcutting towards the limbus. You can see the next stage of the operation, which is formation of a sclerostomy. The diamond knife is used to create a full thickness incision into the anterior chamber. You can see that the eye has been filled with viscoelastic, and this leaks out when we make the full thickness incision with the diamond knife. Here you can see the Kelly’s punch being used to form a sclerostomy. A little fragment of plastic being removed from the punch, which is very reminiscent of the process in a human eye. Again, removing pieces that have been removed by the punch. You can see, returning to the other simulated eye surgery eye, the same process. The formed sclerostomy is then ready for the next step, which is the peripheral iridectomy. You can see the plastic iris is being retracted.

Last Updated: October 31, 2022

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