This video demonstrates ahmed valve implant and phacoemulsification in a female patient with angle closure glaucoma, short axial length, big lens diameter an pseudoexfoliation. Dr. Alward implanted the Ahmed plate first, finished the phacoemulsification part of the procedure and then completed the tube implant.
Surgeon: Dr. Wallace Alward, University of Iowa Carver College of Medicine
DR ALWARD: We are performing Ahmed valve implant with a phacoemulsification in this patient. She has angle closure glaucoma and was also noted to have exfoliation on her lens capsule after being dilated for this surgery. The preferred placement for tube shunts is superotemporal, as there is the most space in this quadrant. This is important even though the Ahmed is not as big as a Baerveldt. Regardless, the Supra temporal quadrant is the most preferred.
We are doing this lady’s surgery under general anesthesia because she is deaf and wouldn’t be able to cooperate with the procedure. I’m going to first place the plate of the Ahmed, I loop the rectus muscles. We don’t need to do this with an Ahmed valve as much as with the Baerveldt, but I encourage it particularly when learning because it gives great exposure. The question is why we put viscoelastic in the anterior chamber with an Ahmed. Sometimes with an Ahmed especially the FP7 valve, like the one we’re putting here. The valve doesn’t work as well as we like, and we can have a shallow anterior chamber early after surgery. So, it is an assurance against flat chamber on day one. It will just gradually be washed out through the tube, so that it will just slow down the flow enough that the chamber will stay formed.
While we first started using the FP7s, unlike the polymethylmethacrylate S2s, we were aware that there were more shallow anterior chambers. So having this viscoelastic flow through just slows things down enough and hopefully keeps that from being a problem. This is a move that I really like, the tissue is tight here and I don’t want to cut her conjunctiva but if I just cut the tenon’s parallel to the rectus muscles, it opens up this quadrant very nicely. You can see that I have really good exposure 10 millimeters back. She has a very short eye; I will mark 10 millimeters but I may not get that far back.
There are two types of Ahmed’s, the FP7 which has a soft plate and there is an S2, which is an older one, which is polymethylmethacrylate, a hard plate. The only time I use the S2’s is if I’m really worried about postoperative hypotony. So, I’m going to irrigate this. I don’t want to push too hard. I just want to push hard enough to get the fluid to go past the valve. If we don’t do this, in theory it will be air locked and may never work. So, the valve is right in this area, It’s important never to touch the valve, you may crush it. And you can see the three holes like on the Baerveldt for fibrous tissue to grow through and keep from developing too large a dome. I’m going to leave the Ahmed valve flat on the eye and slide it in just like sliding in a drawer and I want to make sure that it’s mobile. I use the 0.5 Forceps because it gives me the ability to move the eye around. Again, it’s all about having good exposure. Now we will be suturing the Ahmed valve, the needle has passed partial thickness through the sclera and then passed through the plate.
It’s really important that the needle is flat to the sclera, and I like to hold it in the middle of the curve of the needle and not grab it at the back. If you tie it tight, it will indent the edge of the plate and that’s a good thing.
I am just rotating this knot back. It’s not a big thing with silk, but with the nylon that I normally use, the ends can poke through the conjunctiva. With the calipers I am making sure that I’m far enough back, which I am. I do the plate first, if I do the phaco first, all of the manipulating to get the plate in place just opens up the phaco wound and shallows the anterior chamber. So, I placed the plate and tucked the tube out of the way.
I am making a paracentesis through the clear cornea and injecting viscoelastics. I am trying to flatten the front surface of the lens because she has a small eye and a big lens and exfoliation on the lens capsule. A crescent knife is used here to make clear corneal incision to enter the anterior chamber and with a bent needle I’m starting the capsulorhexis. I’m happy that the capsulorhexis is complete even with her exfoliation. Hydrodissection is performed and then the nucleus is removed using a divide and conquer technique. Iris is prolapsing, which obviously I don’t want it to do. I think some of this has to do with the fact that the eye has synechiae and that the iris is very far forward. I should have probably made my entrance a little farther into the cornea. Obviously, I rather not fight the iris, I don’t think her Iris is going to be a big problem going forward
There is a little bit of debris on her posterior capsule, I’m not going to spend too much time worrying about that I feel lucky to have gotten to the point where I am. We can always do Yag capsulotomy if we need to later on. She’ll definitely have a little Iris atrophy over here, but I don’t think that will affect her.
You can see that her Iris is stuck up to her cornea from her synechiae. So, the game plan was to put the tube under the iris in front of her intraocular lens. Because when someone has synechiae 360 degrees all the way up onto the cornea, there’s absolutely no way of putting the tube in front of the iris without destroying the cornea. I am closing our corneal incision here, the suture looks loose, so I will hydrate some with BSS. Her anterior chamber is surprisingly deep. I had expected with all of her synechiae that we would have to put the tube behind the iris. Her axial length is only 20.9 millimeters, almost nanophthalmic and she has a very thick lens. But surprisingly her iris is way back, so I think we can go anterior to the iris and place the tube deep in the anterior chamber. The anterior chamber is almost too deep to go underneath the iris. Her anterior chamber is probably five corneal thicknesses deep now.
We are entering the anterior chamber with a needle to put the tube inside. As you can see, I’m struggling a little bit with Iris here, but I think that will be fine. I just need to drive it back some more. In general, if you can get it in the front of the eye, it’s easier. For example, in neovascular glaucoma one has to go underneath the iris. So, this tube looks great. It’s deep and it’s not touching the iris. The chamber is very deep now. Because her axial eye length is so short and she has angle closure. This is somebody I will leave on atropine because of the concern about malignant Glaucoma or aqueous misdirection
I will take the cornea next please; I use cornea or whatever patch graft is available. I always hold it over the field because the last thing you want to do is to drop this onto the floor. This is cornea preserved in glycerin. So, it takes a little while to hydrate. Grabbing the anterior part of this graft because I want to tuck the front end down to make it less steep in the front. Corneas are very nice if you can get them, these are corneas are not healthy enough for corneal transplantation. But one can use other material like sclera or pericardium.
If she’d had previous surgery, sometimes it’s hard to get the conjunctiva forward so then I would reach back and pull on tenon’s, because sometimes he gets pushed back by the plate. We’re not going to remove the viscoelastic here, in fact I will be adding a little bit more. As I close the conjunctiva, I want that bite to be deep enough so the wound stays where I put it. So, I’m trying to get a little bit of epi sclera or sclera.
The tube looks good. The chamber is surprisingly deep. And the iris that I beat up looks actually pretty good here. Because of the big lens I expected it to have difficulties with capsulorhexis. I thought that it might go peripherally, which thankfully didn’t happen. And despite her exfoliation, her zonules seem fine. In retrospect, I think I could have made the keratome incision farther into the cornea. I really didn’t expect her Iris to behave that way.
I will now add some viscoelastic. There are many studies looking at mitomycin and Ahmed and Baerveldt implants. There are very conflicting reports, but I think most people feel that if you use might mitomycin, you may have more complications with the plates moving.
So, this suture looks ugly, I think I’ll redo it. I think removing her big round lens is helping her a lot, the chamber is dramatically deep. So, I put the X suture starting inside the wound and that way you don’t have to struggle too hard to bury it.
I am going to give her a second paracentesis down here so that, if we need to deepen her chamber tomorrow, I won’t have to go through the other wound or digging through her conjunctiva. To me she looks great, her Iris looks okay, not perfect. The tube is in wonderful position and the lens is centered.
I am giving her Subconjunctival antibiotics and steroids here. I think I have her pressure a little bit high, got a little carried away deepening anterior chamber, so I’m just going to relieve some pressure here.