AREAS OF CONCERN
In the past, the gold standard was for a surgeon first to perform the trabeculectomy and, approximately 6 months later, proceed with cataract extraction. Although performing cataract surgery as a separate procedure poses a risk to the trabeculectomy, physicians generally felt that the risk was lesser than that of a combined procedure. Because clear corneal surgery reduces the amount of conjunctiva that is traumatized, it decreases inflammation and the risk of failure when the procedures are performed separately. This method generally leaves the patient with relatively poor vision until cataract surgery is complete, however, and separating the procedures also involves greater expense than combining them.
Modern lens implants have lessened physicians' concerns regarding biocompatibility, and it appears that all foldable materials (generally acrylic or silicone) are safe for the human eye. Studies have shown no increase in inflammation or cell deposition with silicone versus acrylic lenses.16-18 I personally tend to use acrylic IOLs owing to didactics and their slightly lesser rate of PCO.
Another area of concern relates to antimetabolites. A few early studies indicated that these agents offered no surgical advantage, but repeat studies emphasizing broad diffuse exposure have shown that using antimetabolites is beneficial.19-24 I usually apply mitomycin C (MMC) at a concentration of 0.2 mg/mL under Tenon's capsule for an exposure time of approximately 90 seconds.
ONE SITE VERSUS TWO
The surgeon may use either a one-site or a two-site procedure. Initially, all my cases were one-site,25 but, after the advent of clear corneal incisions and temporal access, I changed to a two-site procedure. Data suggest that both approaches are equivalent in IOP-reducing effects,14,25-27 but I find that the cataract extraction is much easier when performed temporally. A temporal incision also gives me better access to the anterior chamber and better enables me to avoid causing corneal endothelial damage.
SURGICAL PREPARATION
After dilation, my patients receive three drops of topical bupivacaine 0.75%. Just before they enter the OR, a nurse administers topical 2% lidocaine gel and ensures that the superior conjunctiva receives ample coverage. Because topical drops do not penetrate the gel, the nurse instills the drops of povidone-iodine prior to administering the gel.
THE COMBINED PROCEDURE
After draping the patient and placing a lid speculum, I ask the patient to look down. I then create a 5- to 6-mm, superior, fornix-based peritomy with a Wescott scissors. I rarely need to place a corneal bridal suture. I perform cautery to scleral veins with a 23-gauge cautery (Medtronic Ophthalmics, Jacksonville, FL). Next, I initiate a 4 X 3-mm scleral thickness flap (350 µm) with a trifacet diamond blade and dissect forward into clear cornea with a combined diamond crescent knife. I cut a corneal shield (Merocel; Medtronic Ophthalmics) in half, soak it in MMC (0.2 mg/cc), and place the shield under Tenon's capsule, where it remains for approximately 90 seconds (Figure 1). During this time, I rotate the microscope and pedals temporally.
Figure 1. The author places an MMC-soaked shield under Tenon's capsule.
After removing the sponge and copiously irrigating the MMC-treated area with BSS (Alcon Laboratories, Inc., Fort Worth, TX), I make a stab incision through peripheral clear cornea. Next, I inject 1% nonpreserved lidocaine (0.3 cc) into the anterior chamber. I then fill the anterior chamber with viscoelastic—Duovisc (Alcon Laboratories, Inc.) in eyes with a dilated pupil or Healon5 (Pfizer Inc., New York, NY) in eyes requiring pupil manipulation.
The length of the temporal incision that I create depends on which phaco unit I am using: 3.0 mm with the 1.1-mm flared tip of the Legacy (Alcon Laboratories, Inc.) or 2.75 mm with the 0.90-mm tip of the WhiteStar system on the Sovereign (Advanced Medical Optics, Inc., Santa Ana, CA). After creating a 5.5-mm continuous, circular, curvilinear capsulorhexis, I perform hydrodissection and hydrodelineation with BSS. Phacoemulsification disassembles the nucleus. I generally use a chop technique but will employ other variations when needed.
After I/A, I inject the IOL into the capsular bag (Figure 2) and place—but do not tie—a 10–0 nylon suture across the temporal wound. I leave viscoelastic in the anterior chamber to facilitate the remainder of the trabeculectomy procedure. Next, I rotate the foot pedals and microscope superiorly and then complete the trabeculectomy (or nonpenetrating procedure such as placing the AquaFlow implant [STAAR Surgical Company, Monrovia, CA]). For a trabeculectomy, I enter the eye with a keratome, use a punch28 to perform a peripheral corneosclerectomy, and remove trabecular meshwork. Most of the time, I am removing tissue anterior to the trabecular meshwork. I usually do not perform an iridectomy29 but will do so for highly hyperopic or nanophthalmic eyes.
Figure 2. The author prepares a foldable IOL for insertion.
I reposition the flap with two 10–0 nylon sutures and a slip-knot technique. I adjust the tightness of the sutures in order to obtain good aqueous flow. Next, I suture the conjunctiva and Tenon's layers to the limbus with a running, horizontal mattress suture (10–0 VICRYL in a VAS 100–4 needle; Ethicon Inc., Somerville, NJ) (Figure 3). Using I/A, I remove residual viscoelastic through the temporal corneal incision. This step also initiates aqueous flow through the trabeculectomy site and allows me to verify a watertight closure of the sutured conjunctival peritomy. I close the temporal corneal wound with a 10–0 nylon suture.
Figure 3. The author closes the fornix-based flap with a 10–0 VICRYL suture.
Figure 4. One year after the combined procedure, the bleb is functioning.
POSTOPERATIVE REGIMEN
Patients use antibiotic drops q.i.d. for 1 week. They instill steroid drops intensively for the first few postoperative days and then taper their usage to q.i.d. for a couple of weeks. Depending on the inflammation, I may instruct patients to use steroids for up to 6 weeks postoperatively. If aqueous flow is inadequate, argon laser suture lysis may be performed as early as 1 week or as late as 6 weeks postoperatively. I do not hesitate to use 5-fluorouracil (10 mg)30 as a subTenon's injection to increase aqueous flow (Figure 4).
Supported in part by a grant from Research to Prevent Blindness, Inc., in New York to the Department of Ophthalmology at the University of Utah.
Alan S. Crandall, MD, is Professor of Clinical Ophthalmology, Vice Chair of Clinical Services, and Director of Glaucoma and Cataract at the John A. Moran Eye Center, University of Utah Health Sciences Center, Salt Lake City. He holds no financial interest in the products mentioned herein. Dr. Crandall may be reached at (801) 585-3071.
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