Surgeon: Dr. Jody Piltz-Seymour, Wills Eye Hospital, USA
Dr. Jody Piltz-Seymour: We’re going to be doing an Ahmed valve in a patient with very advanced glaucoma. Her pressures are 50 right now. She had a prior glaucoma surgery up in this area.
I’m going to check to see that the conjunctiva is mobile or not, there is some scarring but we should be able to open up the scarred tissue. We are going to start with the conjunctival peritomy.
We have some scar tissue at the old surgical site that we’re going to have to work through.
We’re just going to dissect a nice conjunctival flap. We’re going to make a relaxing incision. And then we’re going to make that relaxing incision back. I think we can use that regular FP7, the regular Ahmed. So, we’re going to dissect a nice big pocket. Now the Ahmed Valve is smaller and different than the Baerveldt, it doesn’t go underneath the muscles.
But I still like to know where my muscles are so I can see right here the insertion of my muscle, the superior rectus. And we can go deep down and skirts around and grab the lateral Rectus and take a look down at the lateral Rectus too. So, we can see our two muscle insertions.
And we want to put our plate between that. We want to make sure we have a nice deep pocket back here. So, you don’t need to cauterize as widely with the tube than with a trabeculectomy
But it’s nice to do some cautery where you’re going to do your sutures for the plate. And we’re just going to remove some of these inter muscular adhesions.
When you insert the valve, you don’t want to put any pressure over the valve mechanism itself. So, the valve sits right over here. Before I place it all the way back in the pocket, I’m going to prime the valves. So, these valves don’t work without being primed. So I sort of like to secure it in the pocket.
So we get our canula in here. I’m going to pull this up a little bit so you can watch as the valve presses. So watch this area over here and then until you see fluid come out. Starting to open and you want to do it gently you could do it a lot faster than that but you don’t want to press too hard through the valve mechanism. And I very gently squirt about a CC or two of fluid through the valve.
Then I’ll take the 9’0 nylon please. And we’ll make a pass in the scleral tunnel but not too deep.
So I am going to put just a loose throw in here, so I can move the valve a little bit, but have it a bit secure. So just one set of three and then I’ll tie it down later, when I do the other side.
And we’ll just secure this side down now. So we have our plate sutured back, behind the muscle insertions. And that should be about eight to 10 millimeters posterior to the limbus when you’re in the superotemporal quadrant.
And we’re going to see about where we want to cut that tube so it sits nicely in the anterior chamber just about a millimeter or two. And we like to trim it with the bevel.
So this looks like a fit about right in the anterior chamber. But when it goes in straight it’s going to come out a little bit long. So I’m just going to make it a teeny bit shorter. Now I’d like to take a super blade, please and Will make a paracentesis. So when you’re in the superotemporal quadrant you can go in straight, when you’re working in an inferonasal quadrant, you really need to bend the needle in order to get it in the anterior chamber. I’m going to come in parallel to the iris. And then I want to come in to the anterior chamber parallel to the iris and away from the cornea. The 23 gauge makes a very tight fit. But it’s better to struggle a little to get the tube in and to have it to be a very tight seal. So when you do an Ahmed, the valve is working right away, so you don’t put any venting slits in like we did with the Baerveldt.
Get a little bit of security on the valve that way. We’ll take the tutoplast.
Now if you don’t have graft material you can still do valves. When I first started doing valves we didn’t use graft material. And what you do is either, instead of entering with the tube here you could enter farther back and just tunnel until you enter into the anterior chamber or you can make like a trabeculectomy flap but longer, a long scleral flap and put the tube under that scleral flap and then suture the scleral flap down. So those are two different ways of covering the tube other than using graft material.
So the tissue gets rehydrated but it’s a little bit easier to cut when it is dry. So you want to cover the entrance of the tube and as much of the tube as you can. And we’re just going to suture this down and it’s doesn’t it have to be right at the four Corners but four secure sites. And this is tutoplast pericardial graft.
But you can use sclera graft from donor sclera. If there’s an eye bank locally, you can use donor corneas that are not suitable for transplant. So I am going to see where I bring my tissues back to.
The tube and the plate take up a good bit of room and it takes a little bit of effort to tease the tissues back up. And I like to try to incorporate the tenon’s, because the tenon’s will give you extra support more than just the conjunctiva. So we want this to be a nice secure bite. So we’re closing the radial incision that we made, the relaxing incision.
And it’s very important for Ahmed Valves that the wound be watertight, because it’s working right away. And we’ll just suture the other end as well. So we can bring the conjunctiva all the way up to the limbus and cover the tube and as much of the tutoplast as we can. And again I like to incorporate tenon’s into this, gives you a lot more durability. I will give a little gentle irrigation.
And let’s see, at the completion of the case the patient should have a tube in nice position, covered by conjunctiva and covered by the graft. The plate should be sutured about eight millimeters from the limbus. And you want your wounds watertight, you want to make sure that the wounds are not leaking.