A UNIQUE CHALLENGE
Risk factors such as uveitis, neovascular glaucoma, previous surgery, pseudophakia, aphakia, and black race may reduce the success of a filtration procedure. In addition, the success of glaucoma surgery is largely determined by wound healing. After filtering surgery, scar tissue forms as a result of increased vascular permeability and the leakage of plasma proteins at the filtration site; it is to this location that fibroblasts migrate and where collagen undergoes reorientation.
The failure of filtration surgery due to fibroblast infiltration leaves few options for controlling the IOP in a glaucomatous eye. Bleb revision by means of needling is one of few available options to enhance filtration, and MMC is an antineoplastic agent that has been shown to increase the duration of bleb function longer than other antifibrotic agents in such eyes.1,2
INTRAOPERATIVE TRANSCONJUNCTIVAL MMC APPLICATION
The needling technique for failing filtering blebs varies among surgeons, as does the use of antifibrotics and the postoperative care regimen. We favor intraoperative transconjunctival MMC application (ITMA) as an adjunct in the modification of blebs by means of needling. We perform the procedure in the OR under sterile conditions. The anesthesiologist administers an intravenous sedative to the patient. We perform a peribulbar block with 2% lidocaine mixed 1:1 with 0.75% bupivacaine. After preparing the skin surrounding the eye with a 5% povidone iodine solution, we place a drop of this mixture on the eye. The face is draped, and a lid speculum is positioned. We place an 8–0 VICRYL suture (Ethicon Inc., Somerville, NJ) superiorly intracorneally for traction (Figure 1). We then pass a 25-gauge disposable needle subconjunctivally through the dense scar tissue of the bleb (Figure 2). Typically, multiple passes are needed to revitalize the preexisting trabeculectomy site and increase the filtering area. We attempt to raise the scleral flap when possible to further disrupt scar tissue and maximize aqueous outflow. The size of the filtering area increases after the needle's removal. Reformation of the bleb is immediately noticeable (Figure 3).
Figure 1. The authors placed a superior intracorneal traction suture with 8–0 VICRYL. The failing bleb had this appearance preoperatively. (Reprinted with permission from Iwach AG, Delgado MF, Novack GD, et al. Transconjunctival mitomycin-c in needle revisions of failing filtering blebs. Ophthalmology. 2003;110:724-742.)
Figure 2. A 25-gauge needle is advanced subconjunctivally through scar tissue. (Reprinted with permission from Iwach AG, Delgado MF, Novack GD, et al. Transconjunctival mitomycin-c in needle revisions of failing filtering blebs. Ophthalmology. 2003;110:724-742.)
Figure 3. The restored bleb had this appearance postoperatively. (Reprinted with permission from Iwach AG, Delgado MF, Novack GD, et al. Transconjunctival mitomycin-c in needle revisions of failing filtering blebs. Ophthalmology. 2003;110:
724-742.)
Next, we close the entry site with a single 8–0 VICRYL suture. We soak a cut piece of Weck cell sponge in MMC 0.5 mg/mL and hold the sponge to the conjunctival tissue associated with the enlarged filtering area for 6 minutes. After removing the sponge, we irrigate the area with BSS. The eye receives a subconjunctival injection of 0.5 mL betamethasone (6 mg/mL), followed by drops of atropine 1%, gentamicin 0.3%, and prednisolone acetate 1%. The eye is then patched and shielded. The patient continues administering these drops during the follow-up period. Prednisolone dosing depends on the level of inflammation but is typically q.i.d. The administration of atropine depends on the patient's IOP and anterior chamber depth. Both drops are tapered within 4 weeks of surgery, whereas antibiotics are typically discontinued after the first week.
POSTOPERATIVE CARE
The number of visits during the postoperative period varies by case, depending on the characteristics of the eye and the patient. We see patients on the day after surgery, and subsequent visits are scheduled as needed. Some patients receive postoperative subconjunctival 5-fluorouracil injections (5 mg) in the clinic. We have found that those receiving 5-fluorouracil require between one and 11 injections. The number and timing varies based mainly upon the appearance of the tissue and bleb and less on the IOP. Blebs with active fibrosis and vascularization receive a greater number of injections. Ocular hypotensive medications may be needed as well.
To date, we have encountered no intraoperative complications with the ITMA procedure. Postoperatively, small hyphema, choroidal detachment, and blebitis have occurred in a small percentage of cases. All of these complications have resolved within a few weeks with conservative medical management. Some conjunctival epithelial staining may be noted at the site of the ITMA, but it resolves within the first postoperative week.
CONSIDERATIONS
Known advantages of applying MMC transconjunctivally include minimal conjunctival dissection and manipulation, greater control by the surgeon, and a lower risk of the direct spread of the agent into the anterior chamber compared with the injection of MMC into the subconjunctival space, adjacent to or into the bleb. We prefer to perform this procedure in an OR rather than in the clinic at a slit lamp for several reasons. In the OR, there is a lower theoretical risk of infection, we can better visualize the tissues, the eye is more stable during the procedure, and the patient is more comfortable. In addition, the OR is a more controlled environment than the clinic for the use of antimetabolites.
BENEFITS
When strictly defining success as including a 30% reduction in IOP, our preliminary results and those of our colleagues are that 76% of cases undergoing the ITMA procedure are successful at 12 months and require few ocular hypotensive medications. At 24 months, 72% are successful.3
Bleb revision by means of needling with subsequent ITMA allows the incision of scarred tissue with associated restoration and revitalization of the bleb space. We have been performing this procedure for approximately 4 years with good results. When combined with meticulous surgical technique and individualized postoperative care, we believe ITMA is an appropriate adjunct to bleb revision by means of the needling of failing filtering blebs. This procedure is a safe option for restoring bleb function in patients who may benefit from a lower IOP.
Andrew G. Iwach, MD, is Executive Director of the Glaucoma Research and Education Group in San Francisco. He disclosed no financial interest in any products, technologies, or companies mentioned herein. Dr. Iwach may be reached at (415) 986-0835;
admin@glaucomagroup.org.
Mariana Mata-Plathy, MD, is a glaucoma research fellow at the Glaucoma Research and Education Group in San Francisco. She disclosed no financial interest in any products, technologies, or companies mentioned herein. Dr. Mata-Plathy may be reached at (415) 986-0835; admin@glaucomagroup.org.
1. Wilson MR, Lee DA, Baker RS, et al. The effects of topical mitomycin on glaucoma filtration surgery in rabbits. J Ocular Pharmacol. 1991;7:1-8.
2. Parrish RK. Who should receive antimetabolites after filtering surgery? Arch Ophthalmol. 1992;110:1069-1071.
3. Iwach AG, Delgado MF, Novack GD, et al. Transconjunctival mitomycin-c in needle revisions of failing filtering blebs. Ophthalmology. 2003;110:724-742.
