Preparation of Graft
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This video segment explains the manual dissection DALK technique (an option if big bubble DALK cannot be performed). It explains how to perform this technique safely while yet retaining good visual results.
- anterior chamber
- 30-gauge needle
- corneal stroma
- superficial stroma
- residual stroma
- manual dissection
- tissue emphysema
- Melles technique
- Optical recognition
About this video
- Soosan Jacob
- First online
- 12 July 2019
- Online ISBN
- Springer, Cham
- Copyright information
- © The Author(s) 2019
If the big bubble does not form despite multiple attempts, surgery is continued as manual dissection DALK. Air is injected into multiple quadrants to create tissue emphysema, and the stroma is then debulked in layers.
Now this is, again, a patient with keratoconus. You can see the faint Fleischers ring over there. We estimate the size of the graft that would be required. It’s about 7.5 millimeters in diameter.
Now what I do is make a partial-thickness groove with a trephine, taking care not to accidentally penetrate through completely. This can be done either with a suction trephine. Or more carefully, with an open trephine. I prefer to deepen the groove further manually using a bevel-up crescent blade. For then, I know that I am not accidentally going to penetrate into the anterior chamber.
I take a 26-gauge needle that is bent bevel down and inject air into the corneal’s stroma. Now you can see that in this case, I am not getting a big bubble forming. And therefore, what I first do is debulk the superficial stroma using the crescent blade that has now become blunt. It can be done easily by pulling up the superficial layers of the cornea.
Once this is done, I move to a 30-gauge needle, and then, again, try to induce the big bubble to form on the residual stroma. However, you can see again that there is no big bubble forming. But what is happening is that the entire tissue is getting emphysematous. And that is also something that I would desire. And at this point of time, I’m purposely trying to get it to become emphysematous, so that I can continue and perform a manual dissection DALK.
Now the advantage of having these small air bubbles, or the “tissue emphysema,” as it is called, within the cornea’s stroma is that I can get a good guide to the depth of my dissection. The presence of clearly visible emphysematous tissue beneath the blade gives assurance that we are not going to penetrate through into the anterior chamber and that more dissection is possible.
It is not necessary to always go down very deep. If you don’t feel comfortable, you can stop a little short and then proceed as you would normally do with a DALK. The results of predescemetic DALK are also extremely good.
Here in this case, I use a handheld slit lamp to assess the amount of residual stroma tissue left. And since I am satisfied that there is not much, I stop. The other way to do this is by using the Melles technique of optical recognition, where you look at the thickness of the tissue left between an air bubble in the anterior chamber and the residual stroma. A suitably sized donor button stripped of Descemet’s membrane is then punched and sutured onto the recipient bed.
I hope you enjoyed watching this video. Thank you so much.