Manual Dissection DALK
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This video segment shows the surgical technique for Anwar’s big bubble and explains the techniques that can be used to increase chances of achieving an Anwar’s big bubble. It also explains how to deroof the big bubble safely.
- big bubble
- big bubble small bubble
- full thickness
- anterior chamber
- small bubble
- donor button
- refractive error
About this video
- Soosan Jacob
- First online
- 12 July 2019
- Online ISBN
- Springer, Cham
- Copyright information
- © The Author(s) 2019
In this video, I’m going to show you the surgical technique for the Anwar’s big bubble. And the way that you can confirm that you’ve got the Anwar’s big bubble by using the small bubble.
So this is a patient who has got keratoconus. The first thing that you do is to measure or assess the size of the graft that you would want to take. In this case, I’m taking about eight millimeters. 8.5 is too large, since it was going too close to the limbus.
So you can also see this conical area of protrusion out there. It’s wise to go through the topography map of the patient before surgery to have an idea of how steep the cornea is, what is the depth of the anterior chamber, what is the white to white corneal diameter, and so on and so forth.
Now, you can see that I have placed the trephine and made a partial thickness groove centered on the cornea. And I deepen this groove further using a sharp bevel up crescent blade.
One of the tricks to getting a successful big bubble is to have a sufficiently deep groove on all sides. However, care should be taken not to penetrate full thickness, which would result in opening up of the anterior chamber. And though DALK could still be continued with, it would lead to more difficult surgery.
Once the groove is sufficiently deep, a 26-gauge needle is bent bevel down. And it is introduced into the cornea through the depth of the groove, making sure not to penetrate the cornea at any point.
Once it is taken to a sufficiently central point, air is injected into the cornea. And the pattern of air is assessed. You can see that suddenly, from a diffuse emphysematous pattern, the pattern changes to a rapidly expanding big bubble.
The extent of the big bubble can be seen demonstrated there. It has not yet reached the edges of the trephined groove. And therefore, the needle is once again inserted. And some more additional air is injected in, which, as you can see, leads to further expansion of the big bubble till the edges of the trephined groove are reached.
Once this is done, remember that the pressure inside the anterior chamber is high now. So you do a paracentesis and release some of the aqueous. And a paracentesis should be done with care, taking care that you don’t accidentally go and nick the floor of the big bubble, which is basically the pre-Descemet’s membrane.
You can now confirm, if you would still like to do so, the presence of a big bubble in the anterior chamber by injecting a small bubble of air within the anterior chamber. You can see that the small bubble that has been injected is not allowed to go to the center of the anterior chamber. It instead remains in the periphery, rotating all around the central big bubble that is occupying the central part of the anterior chamber.
Once you have thus reconfirmed the presence of the big bubble, you go ahead and do anterior stromal debulking with the crescent blade. This can be done easily. However, it should not be done without care, in order to avoid opening up the big bubble space.
Remember right now that the pre-Descemet’s layer, the Descemet’s layer, and the endothelium has been pushed downwards and is separated from the stroma above by an air bubble. A brave slash is now required, which, as you can see, has to be quick, superficial, and penetrating through those layers of residual stroma.
Once that is done, the stromal space is expanded using viscoelastic. And it is then safe to cut the residual stroma with a Vannas scissor.
As soon as the big bubble is made to collapse by opening its roof with the nick or the brave slash, you can see that the small bubble that was put in the anterior chamber and which was in a peripheral location so far now comes to occupy the center of the anterior chamber and lies right above the pupil. This small bubble there, freely floating, is a guide that the anterior chamber is still well-maintained by the residual pre-Descemet’s, Descemet’s, and the endothelial layers.
So the blunt Vannas has now first been used to divide the residual stroma above the pre-Descemet’s, Descemet’s, and the endothelium into four quadrants. And each of these four quadrants is then cut in line with the trephined groove.
Once all the four quadrants have been removed, it is time to create the donor button. I generally prefer taking a same-sized donor button, in order to decrease the amount of refractive error.