Complications of Glaucoma Surgery and Their Management

Conjunctival Buttonhole

Meticulous technique is the best way to avoid complications associated with glaucoma surgery. This axiom is certainly appropriate in the management of buttonholes of the conjunctiva. Toothed forceps should not be used when handling the conjunctiva. In addition, the conjunctiva should be touched only with the initial incision—whether the fornix or limbal approach is used. Tenon's layer should be manipulated to direct the conjunctival dissection. If a buttonhole does occur, proper management requires immediate attention, because further manipulation will likely enlarge the buttonhole. Complete closure of the buttonhole is necessary to achieve successful results. If complete closure cannot be ensured, then rotation of the site of the trabeculectomy flap to a different area should be considered. Conjunctival buttonholes come in different locations, sizes, and shapes. They can occur near the limbus, in the midportion of the bleb, or posteriorly. An 8-0 or 9-0 polyglactin suture on a vascular needle in a horizontal mattress fashion can be used to close a small hole, or in a running fashion with single-layer or double-layer closure for larger holes. A “clothesline” suturing technique has been described for repair of buttonholes.

Trabeculectomy Scleral Flap Tear/Disinsertion

The surgeon should create a scleral flap that is about two-thirds depth of the total scleral thickness. Occasionally a “ratty” or thin sclera leads to a flap that tears or disinserts. If the tear is small, the flap can be repaired with a 10-0 nylon suture. If the flap disinserts completely, an attempt can be made to reposition the flap by rotating the thicker part of the flap over the sclerectomy. There are reports of successful repositioning of a totally disinserted flap using two 10-0 nylon sutures through the flap base and out the peripheral cornea. Often, however, the quality of the sclera is so poor that placement of sutures through the original flap is not possible because of a “cheesewire” effect, and placement of an additional cover over the flap becomes necessary. Choices of cover material include donor sclera, dura, pericardium, or even fascia lata. Cornea tissue and amniotic membrane have also been used for this repair. A rectangular piece of the material of choice is prepared and fashioned to be approximately 2 mm larger and wider than the trabeculectomy flap. The cover is sutured into place with at least one 10-0 nylon suture to each corner of the material. Postoperatively these sutures may be lysed using an argon laser to increase drainage, as desired.

Intraoperative Bleeding

Excessive bleeding from the iris vessel/root most commonly occurs at the time of iridectomy. Bleeding occurs from cut radial vessels or from a traumatized greater arterial circle within the ciliary body. Such bleeding can be observed, because most iris root/ciliary body bleeding will stop spontaneously within minutes. Applying pressure to the area with a cellulose sponge may speed clot formation. Excess cautery should be avoided because it may lead to vitreous presentation. Cautery should be applied liberally to the scleral flap bed before making the scleral flap incision, and the scleral flap should not be sutured until all of the bleeding has stopped. Premature suturing often leads to postoperative blockage of the internal ostium by the clotted blood.

A suprachoroidal hemorrhage (SCH) can occur during surgery, the hallmark being shallowing of the anterior chamber in the presence of an enlarging dark posterior segment mass visible through the pupil. If an intraoperative choroidal hemorrhage is suspected, the wound should be closed immediately. The anterior chamber should be re-formed with air or a viscoelastic agent. Once the eye has been closed, intravenous acetazolamide and mannitol can be used to lower IOP. Drainage of the hemorrhage may be necessary later. Immediate recognition of SCH is paramount, because an expulsive choroidal hemorrhage is disastrous. The risk of SCH is reportedly higher in patients with high myopia, aphakia, or pseudophakia; in vitrectomized patients; in patients with bleeding disorders; and in the presence of elevated blood pressure. The results of the Fluorouracil Filtering Study showed that only high preoperative IOP was associated with a statistically significantly increased risk of SCH. None of the 63 patients with a preoperative IOP less than 30 mm Hg developed SCH.

Preoperatively it is important to check the IOP when the patient is in the holding area. Intravenous mannitol (1–2 g/kg) is recommended if the IOP is greater than 30 mm Hg. Mannitol has an onset of action of less than an hour, so if it is given before the surgery, the IOP should be significantly lower before an intraocular incision is made. Furthermore, blood pressure should be monitored and treated if it is elevated.

Intraoperatively the risk of SCH may be reduced by decompressing the eye slowly and carefully with the initial paracentesis. In addition, it is important to suture the scleral flap snugly and to achieve meticulous conjunctival wound closure. Leaving the eye partially filled with viscoelastic can be considered to minimize the likelihood of anterior chamber shallowing in the early postoperative period.