CASE PRESENTATION
A 60-year-old male with a complicated ocular history is referred for the management of elevated IOP in his left eye. The patient recalls blunt trauma to his left eye 30 years earlier that caused a secondary cataract. Thirteen years ago, he underwent cataract removal and the implantation of an anterior chamber IOL (ACIOL). The patient does not know whether a vitrectomy was performed at any point or if the cataract surgery was complicated in any way.
Two years prior to the current evaluation, the patient consulted a cornea/refractive surgeon about blurred vision in his contralateral eye. The patient was found to have a visually significant cataract in his right eye and, incidentally, inferior microcystic corneal edema in his left eye. His BCVA was 20/25 OS. The patient was diagnosed with corneal decompensation from a poorly sized ACIOL and underwent ACIOL exchange with Descemet's stripping automated endothelial keratoplasty (DSAEK) in his left eye. The surgery was complicated by poor adhesion of the donor lenticule, which required the placement of an anchor suture on postoperative day 2 and a penetrating keratoplasty (PKP) 3 weeks after surgery. His postoperative IOP was 30 to 45 mm Hg on maximally tolerated IOP-lowering medications, and he was referred to a glaucoma specialist.
On examination, the patient's BCVA is 20/25 OD and 20/400 OS. There is no relative afferent pupillary defect. The IOP measures 11 mm Hg OD and 42 mm Hg OS. Ophthalmoscopy is unremarkable in the patient's right eye. His left eye has a scarred superior conjunctiva with visible scleral sutures. There is evidence of microcystic corneal edema with an otherwise clear corneal graft. The ACIOL is positioned adequately without evidence of active inflammation of the anterior chamber. The pupil is irregular with two peripheral iridectomies. There is no evidence of vitreous in the anterior segment, and the posterior hyaloid face is not visible. Ninety degrees of superonasal peripheral anterior synechiae are present on gonioscopy in the patient's left eye, and the angle is otherwise open. A fundus examination reveals thinning of the neuroretinal rim inferotemporally and superotemporally in his left eye. The remainder of the fundus examination is unremarkable.
Comments on the Placement of a Tube
ABD: This patient has evidence of unilateral glaucoma with IOPs that cannot be controlled medically. How would you manage the patient to achieve both long-term IOP control and survival of the corneal graft?
DLB: At the Bascom Palmer Eye Institute in Miami, my colleagues and I prefer to place tube implants in patients with multiple prior ocular surgeries and pseudophakia.1 Tube implants could compromise a preexisting corneal transplant. The ACIOL may also compromise the PKP. Although prospective studies have yet to show that an appropriately positioned tube will cause the failure of a preexisting PKP, clinical experience suggests that graft failure after a tube's placement should still be a concern.
Francisco Fantes, MD, a colleague, places tubes in the vitreous cavity in eyes with corneal transplants or otherwise compromised corneas in conjunction with a complete vitrectomy performed by a vitreoretinal surgeon. This approach may improve the chances of the graft's survival. I prefer to place the tube within the anterior chamber if there is no evidence of crowding. I performed a similar case recently in which I placed the tube as far posteriorly within the anterior chamber as possible, directly on top of the ACIOL, with the thought that mechanical stress would be less likely to cause anterior movement of the tube.
If I cannot place the tube in the anterior chamber, the patient must undergo a fairly extensive operation involving multiple subspecialists. Given that this patient has an IOP of 42 mm Hg, a pars plana vitrectomy with a posteriorly placed tube leaves him at increased risk of a suprachoroidal hemorrhage. A trabeculectomy may be another option, although I suspect the superior conjunctiva is scarred from his prior surgeries.
FAM: What kind of implant would you recommend?
DLB: The Bascom Palmer Eye Institute is involved in a prospective, randomized trial comparing the Baerveldt glaucoma implant (model 350; Advanced Medical Optics, Inc., Santa Ana, CA) to the Ahmed Glaucoma Valve (model FP7; New World Medical, Inc., Rancho Cucamonga, CA). I think that either device could be used in this patient. Historically, Ahmed implants have not reduced the IOP to as great an extent as Baerveldt implants in the long term because of their smaller surface area. Because the patient in this case does not exhibit an afferent pupillary defect, however, his IOP may not have to be exceedingly low. The Ahmed FP7 can provide a fairly immediate, reasonable reduction in IOP. In order to obtain a lower IOP with the Baerveldt 350, my colleagues and I have employed a modification of the fenestration technique proposed by James Brandt, MD, in which we place a 9–0 or a 10–0 monofilament Vicryl suture (Ethicon, Inc., Somerville, NJ) within a single slit. When I use this technique, I occasionally will find that a bleb forms between the patch graft and plate. We do not have any evidence, however, to support using one implant over the other. We have just completed recruitment of our 276th patient for our study, and we currently await the 1-year results.
RNW: Would you explain the technique you use for fenestration? What sort of needle do you use, and how is the suture placed? Is the tube still ligated?
DLB: A cutting needle must be used. Occasionally, the nursing staff will open a 9–0 Vicryl suture on a BV needle, which defeats the purpose of the maneuver. The 9–0 or 10–0 monofilament Vicryl suture keeps the fenestration open. The suture dissolves in 4 to 6 weeks, perhaps around the same time that the ligature suture dissolves. When the ligature suture disappears, the small fenestration becomes inconsequential, as flow will be directed posteriorly through the tube. I use a 10–0 Vicryl suture based on its availability. Dr. Brandt uses a 9–0 Vicryl suture. I leave about a 1-mm tail on each end of the tube after passing the needle. One must be careful not to disturb this tail for the remainder of the surgery. Posteriorly to anteriorly, I place a ligature suture, then the fenestration suture, and finally the patch graft. I find the fenestration suture works more reliably than the venting technique that my colleagues and I described in the literature in the past.2
RNW: To summarize, you would prefer to place a glaucoma drainage device for this particular patient and have no preference of implant (Ahmed FP7 or Baerveldt 350). You still incorporate a ligating suture with the Baerveldt glaucoma implant but also create a fenestration with a Vicryl suture to control pressure in the immediate postoperative period. Also, you would prefer to place the tube as posteriorly as possible within the anterior chamber.
ABD: Part of the concern over placing a glaucoma drainage device within the anterior chamber in the presence of a corneal graft involves the tube's migration inside the chamber with any mechanical stress, including blinking and rubbing of the eye. Tucking the tube beneath the ACIOL would eliminate this concern, although it might increase the risk of iris or vitreous incarceration within the tube.
Comments on Vitrectomy
RNW: In an eye that already has an ACIOL and might have undergone a prior anterior vitrectomy, how complete should the vitrectomy be for the tube to be placed posterior to the ACIOL? Should a total vitrectomy be performed if the tube is going to be placed via a pars plana approach, even if no vitreous is visible by ophthalmoscopy? Is there a particular technique you would use to identify the vitreous to obviate the need for a pars plana vitrectomy before placing a pars plana tube?
DLB: I cannot overemphasize the importance of performing a complete pars plana vitrectomy before the placement of a pars plana tube. The pressure gradient between the posterior segment and the plate draws vitreous into the tube. I have used intravitreal Kenalog (Bristol-Myers Squibb Co., Princeton, NJ) to identify the vitreous for anterior vitrectomy. I have never used it for the placement of a pars plana tube, although I have used Kenalog during complicated cataract surgery. The vitreous surgeons at the Bascom Palmer Eye Institute will use scleral depression to visualize and mechanically shorten the vitreous skirt, because we have had cases in which the pars plana tube became occluded despite an apparently complete vitrectomy. I would consider placing the tube in the anterior chamber in an aphakic eye or beneath the ACIOL in a case such as this one if no vitreous were visible. First, I would explain to the patient that he might require vitreoretinal surgery if vitreous entered the tube.
RNW: My approach is the same. One reason I thought this case was interesting was that it highlights the use of Kenalog to identify vitreous posterior to the iris. My colleagues and my use of preservative-free Kenalog may obviate the need for a pars plana vitrectomy.
ABD: When used for staining and not as an anti-inflammatory agent, a 1:10 dilution of Kenalog with balanced salt solution works quite well. Kenalog is dispensed as a suspension, and only a minute amount of Kenalog is needed to visualize the vitreous. A diluted preparation of Kenalog allows for quick visualization of the vitreous without copious irrigation with fluid, which may mechanically displace the vitreous.
RNW: My colleagues and I had the same concern about the placement of the tube. In an eye with a PKP, an unstable tube can damage the cornea. We therefore employed this alternative approach, which involves tucking the tube posterior to the ACIOL.
ABD: Somewhat fortuitously, the ACIOL was vaulted above the iris in this eye. Our intention during surgery was to place the tube as far back as possible. Because there was a clear space between the ACIOL and the iris, we attempted to direct the tube into this location (Figure 1). Several important considerations influenced our decision, including the absence of visible vitreous on ophthalmoscopy and the location of the ACIOL's haptics. The superior conjunctiva was too scarred for us to place the tube superotemporally, so we placed the plate inferonasally. With a traction suture in place and the eye rotated superotemporally, we could easily direct a 23-gauge needle to create a fistula pointed toward the space between the ACIOL and iris. We then sequentially trimmed the tube, bevel up, to confirm its placement. Ideally, the tube would rest near the pupillary margin with the bevel oriented upward to minimize the risk of iris incarceration. We reconfirmed the placement of the tube after securing it to the sclera with an 8–0 nylon cross-stitch.
CONCLUSION
This patient with an ACIOL, PKP, and, in all likelihood, a prior vitrectomy received an Ahmed Glaucoma Valve FP7 placed inferonasally for optimal IOP control. The tube was placed between the iris and optic of the ACIOL to minimize mechanical trauma to the cornea and improve the chance of the graft's long-term survival. Although ophthalmologists can use Kenalog to stain the vitreous to determine the optimal placement of a tube, the agent was not used in this case because the anterior segment to the midvitreous cavity was optically clear. Placing the tube in the pars plana is an alternative approach to reducing IOP in patients such as this one, but the procedure can require extensive, multidisciplinary surgeries that will not necessarily improve surgical outcomes.3,4 This patient has done well thus far with a clear graft and excellent control of his IOP, most recently measured at 6 mm Hg.
Section editor Robert N. Weinreb, MD, is Distinguished Professor of Ophthalmology and Director of the Hamilton Glaucoma Center, University of California, San Diego. He acknowledged no financial interest in the products or companies mentioned herein. Dr. Weinreb may be reached at (858) 534-8824; weinreb@eyecenter.ucsd.edu.
Donald L. Budenz, MD, MPH, is Professor of Ophthalmology at Bascom Palmer Eye Institute in Miami. He acknowledged no financial interest in the products or companies mentioned herein. Dr. Budenz may be reached at (305) 326-6384; dbudenz@med.miami.edu.
Amish B. Doshi, MD, is the Chief Fellow at the Hamilton Glaucoma Center, University of California, San Diego. He acknowledged no financial interest in the products or companies mentioned herein. Dr. Doshi may be reached at (858) 534-3519; adoshi@glaucoma.ucsd.edu.
Felipe A. Medeiros, MD, PhD, is Associate Professor at the Hamilton Glaucoma Center, University of California, San Diego. He acknowledged no financial interest in the products or companies mentioned herein. Dr. Medeiros may be reached at fmedeiros@eyecenter.ucsd.edu.
