Glaucoma tube placement into the anterior chamber may increase the risk of corneal endothelial injury and lead to corneal decompensation or graft failure, especially in eyes with shallow anterior segments, compromised corneal endothelial function, or previous keratoplasty.1–5 Tube-endothelium contact during eye rubbing, eye movement, or blinking may result in progressive mechanical endothelial damage.6,7 Insertion of the tube into the anterior vitreous cavity after pars-plana vitrectomy maximizes the distance between the tube and the cornea. This procedure has become common practice in patients with concurrent or previous corneal transplantation, corneal endothelial pathology, or shallow anterior chamber.6–10 Although pars-plana vitrectomy is relatively safe in experienced hands, vitrectomy and insertion of the tube into the posterior segment carries significant risks, such as retinal detachment, greater postoperative inflammation, endophthalmitis, vitreous hemorrhage, or vitreous incarceration in the tube lumen.6,7
In patients with posterior chamber intraocular lens (PCIOL) pseudophakia, the ciliary sulcus is a potential anatomic space for tube placement. This space is bounded anteriorly by the iris-pigmented epithelium, posteriorly by the ciliary processes, and more centrally by the anterior zonular fibers and lens capsule. Encouraging short-term results in pseudophakic glaucoma patients who underwent implantation of a tube into the ciliary sulcus have been reported.11,12 Herein, we report midterm results of our initial case series11 and an additional 9 new cases who underwent implantation of the silicone tube of the Baerveldt glaucoma implant (BGI) into the ciliary sulcus.
MATERIALS AND METHODS
This retrospective, noncomparative, interventional case series study adhered to the tenets of the Declaration of Helsinki and the New York Eye and Ear Infirmary institutional review board guidelines. Surgeries were performed by 2 of the authors (C.T. and J.L.) at 1 center (New York Eye and Ear Infirmary, NY).
All charts from glaucomatous patients who underwent insertion of a BGI with the silicone tube placed in the ciliary sulcus between 1998 and 2007 with at least 1 year of follow-up were reviewed. We have previously reported initial short-term results from 8 of these patients.11 Patients were either pseudophakic (PCIOL placed in the capsular bag) or underwent cataract extraction and IOL placement at the time of the BGI implantation. All patients who underwent BGI surgery had uncontrolled intraocular pressure (IOP) on maximally tolerated medical therapy. Data collected included preoperative and postoperative IOP, number of antiglaucoma medications, best-corrected visual acuity, surgical complications, and any subsequent related events or procedures. To accommodate the small sample size and nonparametric variables, Wilcoxon signed-rank test was used to compare continuous data in patients preoperatively and postoperatively. Statistical significance was set at P<0.05.
Briefly, a 350 mm2 BGI (Advanced Medical Optics, Santa Ana, CA) was used in each case. The tube was then trimmed bevel-up to have an intraocular segment approximately 4 to 5 mm long, and a 7-0 polyglactin suture was used to ligate the silicone tube about 2 mm proximal to the plate. Before tube insertion, sodium hyaluronate (Healon, Advanced Medical Optics) was injected into the posterior chamber sulcus with a 27-gauge cannula. The tube was then carefully inserted through a scleral tunnel (starting 2 to 2.5 mm posterior to the limbus) directed towards the center of the pupil. It was placed parallel to the iris and PCIOL, ensuring that half of the bevel-up sector was within the pupil. This technique and associate figures have been previously described.11
In this follow-up study, we studied 17 eyes of 17 patients. Baseline characteristics for each patient are given in Table 1. For all 17 patients, mean age and follow-up period were 67.5±15.3 (SD) years (range: 39 to 94 y) and 37.2±18.9 months (range: 14 to 72 mo), respectively. Most of the patients were pseudophakic (16 out of 17) before surgery, and 1 patient underwent a simultaneous cataract extraction and tube placement. Five of the patients had a previous corneal transplant. The IOP was reduced from a preoperative (last IOP reading before surgery) mean of 28.4±12.2 mm Hg (range: 12 to 56 mm Hg) to a postoperative (IOP value recorded in the last follow-up visit) mean of 12.1±5.9 mm Hg (range: 3 to 26 mm Hg) (P<0.001). Eighty-two percent of the cases (14 out of 17) had an IOP between 7 and 18 mm Hg at the end of the follow-up period (Table 2). The mean number of antiglaucoma medications was reduced from 3.4±1.4 (range: 0 to 5) to 2.0±1.4 (range: 0 to 4) during the same period (P=0.01). Finally, there was no statistically significant difference with respect to mean best-corrected visual acuity (logMAR) at baseline [1.3±1 (range: 0.2 to 3)] and at last follow-up visit [1.7±1.3 (range: 0.2 to 4); P=0.11].
Considering only the 8 eyes from our previous case series,11 mean age and follow-up period were 76.4±9.6 years (range: 62 to 94 y) and 45.3±15.2 months (range: 18 to 63 mo), respectively. Mean IOP was reduced from 28.3±14.4 (range: 12 to 56 mm Hg) to 11.1±6.1 mm Hg (range: 7 to 26 mm Hg) (P=0.01) at the end of the follow-up period. The mean number of antiglaucoma medications was reduced from 2.9±1.6 (range: 0 to 5) to 2.0±1.5 (range: 0 to 4) during the same period (P>0.05).
There were no intraoperative complications. Regarding postoperative complications, 21 months after the surgery, patient 1 presented with the iris plugging the tube, which was thought to be due to tube retraction and was managed with chronic mydriasis. No further complications were observed, and the patient maintained a stable IOP (7 mm Hg) without additional antiglaucoma drops. In addition, patient 16, who had advanced glaucoma and had undergone multiple intraocular surgeries, developed chronic hypotony (follow-up, 16 mo). In the eyes that underwent ultrasound biomicroscopy or slit-lamp–adapted optical coherence tomography evaluation, there was no evidence of cleft, iridodialysis, ciliary body detachment, or tube rubbing against the posterior surface of the iris (Fig. 1).
Midterm results suggest that the insertion of a silicone tube into the ciliary sulcus is a safe and effective alternative surgical approach in pseudophakic patients. Pars plana placement is often used in patients with complicated anterior chamber pathology. Implantation into the ciliary sulcus could prevent deleterious complications associated with a pars plana vitrectomy or anterior chamber placement in such patients. This procedure itself is comparable with the conventional tube placement in the anterior chamber and is less time-consuming than a vitrectomy.
As with the previously reported series, major postoperative complications in these larger series were uncommon.11 During the follow-up period, no postoperative inflammation or posterior synechiae were noticed. Iris incarceration was noted in 1 patient 21 months after the surgery, which was most likely secondary to tube retraction and was successfully treated with chronic mydriasis. Another patient (number 16), who had advanced primary open-angle glaucoma, developed chronic hypotony. This eye had hand motion visual acuity and had undergone 2 antiglaucoma surgeries previously. During the entire 16 months of follow-up, IOP ranged between 2 and 4 mm Hg. There was no evidence of over filtration and the case was managed conservatively. Despite inserting the tube into a limited space with such a close proximity to the iris, indirect evidence of the tube rubbing against the posterior surface of the iris was seen only in 1 case (patient 1). An overall absence of anterior uveitis and pigment release suggests a low risk of contact between the tube and the iris surface. The placement of the beveled tube tip into the pupillary area seems to avoid this complication, thus preventing intraocular inflammation. None of the patients was aware of the presence of the tube near the visual axis.
Corneal endothelial failure is the most common long-term complication of anterior chamber shunts. Sulcus placement helps to avoid damage to the cornea by preventing the tube from coming into contact with corneal endothelium and avoiding trauma to the angle recess. Notably, patients 3, 5, 7, 11, and 15 had undergone a previous corneal graft before the tube was placed into the posterior chamber sulcus. Of these 5 eyes, 1 (patient 15) was already presented with graft failure before the BGI implant. Normally, a pars plana vitrectomy would have been indicated to prevent graft endothelial damage. However, no signs of corneal graft rejection were observed in patients 3, 5, 7, and 11 after a follow-up of 50, 63, 43, and 44 months, respectively.
Sulcus placement is easily performed by an ophthalmologist with experience in glaucoma surgery. An important fact that facilitates the insertion of the tube into the sulcus is that this anatomic space increases its anterior-posterior length after cataract extraction, due to the smaller thickness of the implant compared with the crystalline lens. We believe the most important technical points are the injection of sodium hyaluronate between the posterior chamber implant and the iris before inserting the tube, and orienting the silicone tube bevel-up, with the pupillary margin covering part of the tube bevel. However, a larger sample size is needed to determine the frequency of complications and how best to prevent them.
This study is limited by its retrospective design, small number of patients, and lack of corneal endothelial cell counts before this procedure. This technique can be readily applied to other glaucoma drainage valves as most of them have a silicone tube of identical dimensions to the Baerveldt implant. However, this procedure might not be effective in cases of uveitic glaucoma or glaucoma with concurrent episodes of intraocular inflammation. Microscopic and continuous touch may occur between the tube and the iris, resulting in further intraocular inflammation. Future studies could compare the efficacy and safety of this procedure with pars-plana tube insertion.
In summary, our findings suggest that placement of a silicone tube into the ciliary sulcus in pseudophakic eyes is an effective alternative for glaucoma management with minor postoperative complications. This relative simple technique not only avoids the need for a pars-plana vitrectomy in eyes with anterior segment abnormalities (shallow anterior chamber, compromised corneal endothelium, or previous keratoplasty), but also seems to reduce corneal endothelial loss, as most patients had no significant visual acuity loss during follow-up.
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