Considerations on Day of Glaucoma Drainage Implant Surgery

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Primary authors	Jeffrey M. Zink, MD

On the day of aqueous drainage implant surgery, there are some important things to consider to help achieve desired results. Although it is necessary to plan in advance prior to surgery, there are some important considerations on the actual day of surgery as well. Attention to detail regarding preparations in the holding area, preoperative equipment check, anesthesia type, operative positioning for surgeon and patient, last-minute implant considerations, and intraoperative tissue and anatomical assessments can help to achieve more optimal results.

Holding Area

The holding area is where you want to make sure that the patient understands the surgery and that you answer any last-minute questions or concerns. The surgeon must make sure the patient has signed the consent form for the appropriate tube shunt surgery and that the correct eye is scheduled. Mark the patient’s operative eye in the holding area and confirm the correct eye with the patient. Review the surgical consent form and ensure that placement of a tissue patch graft is included in the surgical consent form. Ensure that the patient is willing to accept donor tissue, as most patients do not consider glaucoma surgery as involving transplanted tissue. Some patients will not accept transplanted tissue for religious reasons, and it is important to have this conversation and make them aware that transplanted patch graft material is part of this type of glaucoma surgery. If the patient is on warfarin, I like to check an international normalized ratio blood test on the day of surgery. If the patient is taking clopidogrel or other blood thinners, ask when these medications were discontinued. If blood thinners were not stopped, you may want to consider topical or intraoperative sub-Tenon’s anesthesia.

Preoperative Check

It is important to make sure you have the correct implant available prior to the surgery. I like to have a second implant of similar type available in case one is defective or if the device is damaged during surgery. I also recommend having a tube extender available, especially in training programs. If the tube is inadvertently cut too short, a tube extender will allow the tube to be extended and placed at the desired length in the anterior chamber. Make sure that the donor patch graft material is present and stored appropriately. If there is the possibility of placing an inferior tube, I prefer to have corneal patch graft available for cosmetic reasons. Corneal patch material is clear and does not show up on the sclera as conspicuously as scleral patch grafts when placed inferiorly. For cosmesis, processed pericardium is preferable to sclera but less preferable than cornea. If patch graft tissue is ordered from an eye bank, make sure to check the eye bank paperwork to ensure that all proper serologic testing has been done and the appropriate titers are negative.

Anesthesia

Anesthesia for glaucoma drainage implant surgery can vary from topical with subconjunctival supplementation, peribulbar block, or retrobulbar block. The type of anesthesia that is needed should be tailored to the level of complexity of the case in terms of tissue manipulation and the patient’s ability to cooperate during the surgical procedure. I prefer intraoperative sub-Tenon’s anesthesia or a peribulbar block in the holding area. I use a long block consisting of a 50:50 mixture of 0.5% marcaine and 2% lidocaine. In complex cases that require extensive tissue dissection and manipulation, a standard retrobulbar block may be required.

Positioning

The importance of proper patient and surgeon positioning in the operating room cannot be overstated. Make sure your patient is comfortable and you have adjusted the head positioning so that it minimizes neck and back discomfort during the surgery. If your patient is not comfortable, they are more likely to move suddenly. Consider taping the patient’s head to minimize the risk of sudden movement. Some surgeons prefer to use a wrist rest to stabilize their hands during surgery. I like to sit superiorly during aqueous drainage implant surgery. Some surgeons prefer to sit slightly offset from 12 o’clock to the side of implant placement location to give them better access to the superior temporal quadrant.

Implant Considerations

Intraoperative examination is important when determining implant location. If patients have a very tight orbital space, you may favor implanting a smaller plate tube shunt. Sometimes, you may not be able to determine the appropriate size of the implant until you have started the dissection and better evaluate orbital anatomy in the operating room. In patients with a prior scleral buckling procedure, I prefer a lower profile tube shunt, such as a Baerveldt 250 mm² implant, which can be sewn to the buckle itself or just posterior to the buckle, depending on the buckle location.

Normally, the preferred location of implant placement is the superior temporal quadrant. Intraoperatively, you may notice extensive conjunctival scarring superiorly in some cases. The conjunctiva may also be very thin and friable from previous trabeculectomy surgery and mitomycin C (MMC) exposure. In these cases, the inferior nasal quadrant can be a great alternative location for implant placement. If you think that inferior tube shunt placement may be necessary, it is a good idea to have corneal tissue available for patch material, as previously mentioned, to provide a less conspicuous patch graft. A scleral patch graft can be quiet visible when placed inferiorly. In addition, I prefer a tube that achieves a lower profile, such as the Baerveldt 250 mm² or 350 mm² for inferior tube placement. Although Ahmed implants can be placed in the inferior nasal quadrant, I have found that an implant with a lower profile is a better alternative cosmetically.

Conjunctival Closure Considerations

In general, with healthy conjunctival tissue, I prefer closure with an 8-0 braided Vicryl suture on a TG-140 needle. For very friable tissue, or tissue with previous MMC exposure, a 9-0 monofilament Vicryl suture on a VAS -100 needle works well. Monofilament Vicryl can be used in routine cases, but it costs more than braided Vicryl and is usually not necessary.

Key Points

Attention to detail and being prepared on the day of surgery is important to be able to provide optimal patient care.
If considering inferior glaucoma drainage implant placement, consider having corneal patch tissue and a lower-profile implant, such as a Baerveldt, available to achieve more desirable cosmetic results.