Purpose
To evaluate long-term complications related to glaucoma drainage devices in patients undergoing Boston type 1 keratoprosthesis surgery.
Design
Retrospective case series.
Methods
All patients who underwent Boston type 1 keratoprosthesis surgery at the University of California, Davis, between 2004 and 2010 were included. Preoperative and postoperative data were reviewed. Twenty-five eyes with glaucoma drainage devices were highlighted. Visual acuity and postoperative complications were tracked at postoperative months 1, 3, 6, 9, and 12 and at annual intervals thereafter.
Results
Forty eyes of 35 patients were evaluated with an average follow-up of 33.6 months. Conjunctival breakdown occurred in association with 10 glaucoma drainage device implants in 9 eyes. Eleven eyes had glaucoma drainage devices placed before keratoprosthesis surgery, 3 eyes underwent glaucoma drainage device placement at the time of surgery, and 2 eyes had a glaucoma drainage device placed after surgery. All but one of the eroded glaucoma drainage devices were placed before surgery. Associated complications included endophthalmitis, hypotony, and keratoprosthesis extrusion, with 6 glaucoma drainage devices requiring removal. Long-term beset-corrected visual acuity was maintained better in eyes in which glaucoma drainage device erosions did not develop.
Conclusions
One of the main challenges with keratoprosthesis surgery is treating concurrent glaucoma. Glaucoma drainage devices have been advocated as a way to address this long-term complication, but this series suggests that glaucoma drainage device-related complications can cause significant vision loss.
Over the past 2 decades, keratoprosthesis surgery has offered new hope for patients with corneal blindness who otherwise would be poor candidates for traditional penetrating keratoplasty. In the United States, the most commonly used device is the Boston type 1 keratoprosthesis, which was approved by the Food and Drug Administration in 1992. The complications of the Boston type 1 keratoprosthesis have been well documented in the literature and include retroprosthetic membrane formation, persistent epithelial defects, sterile vitritis, infectious endophthalmitis, retinal detachments, keratoprosthesis extrusion, and glaucoma.
Glaucoma continues to be one of the most difficult complications to manage in patients with a keratoprosthesis. The ability to measure and monitor intraocular pressures and glaucomatous damage accurately after placement of a Boston keratoprosthesis continues to elude corneal surgeons as patients lose vision to this disease. Glaucoma drainage devices are a common surgical option to help intraocular pressure control when medical therapy is insufficient. We report our experience with long-term complications related to glaucoma drainage devices in the setting of keratoprosthesis surgery.
Methods
A retrospective chart review of all Boston type 1 keratoprosthesis implantation procedures performed at the University of California, Davis (UC Davis) between May 2004 and May 2010. The Boston type 1 keratoprosthesis was obtained from the Massachusetts Eye and Ear Infirmary (Boston, Massachusetts, USA). All surgeries were performed by a single surgeon (M.J.M.) using the technique as described in the initial Boston Keratoprosthesis Study Group.
After surgery, we routinely placed a soft Kontur contact lens (Kontur Kontact Lens, Co, Inc, Hercules, California, USA) of 16.0-mm diameter and started patients on a short course of medroxyprogesterone 1% eye drops in addition to long-term antibiotic and anti-inflammatory eye drops primarily consisting of either fortified vancomycin 50 mg/mL eye drops or a fourth-generation fluoroquinolone eye drop 4 times daily and prednisolone acetate 1% eye drops 4 times daily. Adjustments were made to this postoperative regimen depending on the surgeon’s assessment of the individual patient’s situation. Visual acuity and postoperative complications were recorded at postoperative months 1, 3, 6, 9, and 12 and at annual intervals thereafter.
Surgical Technique for Glaucoma Drainage Device Placement
Of the 16 eyes reviewed in this study, 4 eyes had glaucoma drainage devices (5 glaucoma drainage devices) placed at institutions outside of UC Davis. The surgical reports for these glaucoma drainage device placements were not available for review. The remaining devices were placed at UC Davis. The following describes the routine surgical technique for placement of a glaucoma drainage device at UC Davis. The decision for the type, location, and timing of placement of the glaucoma drainage device was at the discretion of the glaucoma surgeon.
Patients who received a Baerveldt glaucoma implant (BGI; Abbott Laboratories Inc., Santa Ana, California, USA) received a 350-mm 2 device placed underneath the superior and lateral rectus muscles in the superior temporal quadrant approximately 9 mm posterior to the limbus. The implant was secured to the sclera with either 8-0 or 9-0 nylon sutures through the implant’s anchoring holes. The knots were rotated into the implant’s anchoring holes to prevent erosion of the knot through overlying conjunctiva. Because of the nonvalved nature of the implant, the tube portion was ligated with either a 7-0 or 8-0 polygalactin (Vicryl; Ethicon, Inc, Somerville, New Jersey, USA) suture followed by confirmation of occlusion. The option for tube fenestration was at the discretion of the surgeon. The tube was placed into the anterior chamber through a 23-gauge needle tract and was secured to the sclera with 8-0 or 9-0 nylon sutures. Tutoplast allograft pericardium (Tutoplast; IOP, Inc, Costa Mesa, California, USA) was used to cover the tube. Subconjunctival injections of antibiotic and corticosteroids were placed at the end of the procedure. Postoperative care included administration of topical prednisolone acetate 1% and a topical antibiotic.
Patients had either a limbus-based conjunctival flap or a fornix-based conjunctival flap created for the placement of the glaucoma drainage device. The limbus-based conjunctival flap was created by making an incision through conjunctiva and the Tenon capsule at least 8 mm posterior to the limbus in the superior temporal quadrant. Closure of the incision was performed with 9-0 Vicryl sutures in a running locking fashion through the Tenon fascia followed by a running suture through conjunctiva with the same suture material. The fornix-based conjunctival flap was created by making an incision through conjunctiva at the limbus with a peritomy extending 4 to 6 clock-hours of the limbal circumference. The incision was radialized in the inferior temporal quadrant. Closure of the conjunctiva was performed with 8-0 or 9-0 Vicryl anchoring sutures at the wings of the conjunctival incision. Closure of the radialized incision was performed in a running fashion. The conjunctiva along the length of the limbus was not closed with sutures. There were no specific indications for choosing either a limbus-based or fornix-based conjunctival flap except for surgeon preference for each approach.
Eyes that had a pars plana BGI first underwent pars plana vitrectomy performed by the vitreoretinal service at UC Davis. The procedure for placing the glaucoma drainage device is as outlined above except that the tube is placed into the posterior chamber through the pars plana 3 mm posterior to the limbus. Eyes that had a stage I BGI placed underwent the same surgical procedure, however, the tube was inserted at a later date when IOP control was needed. The conjunctival flap is closed with the tube buried underneath the conjunctiva superior temporally.
Ahmed glaucoma drainage devices (New World Medical Inc., Rancho Cucamonga, California, USA) were placed in a similar manner as BGI implants. The Ahmed implants typically were placed in the superior temporal quadrant, but did not need to be inserted under the rectus muscles. Additionally, given the valved nature of the implant, no ligation sutures or tube fenestrations were placed. The Ahmed tubes also were placed into the anterior chamber through a 23-gauge needle tract and were secured to the sclera with 8-0 or 9-0 nylon suture. Tutoplast allograft pericardium was used to cover the tubes at the close of the case.
Results
Table 1 summarizes the patient demographics of the complete study group. Forty eyes of 35 patients were evaluated. The underlying preoperative diagnoses are outlined in Table 1 .
| No. of eyes | 40 |
| No. of patients | 35 |
| Average age (range), years | 52.9 (2 to 86) |
| Average follow-up time (range), months | 33.6 (5.2 to 72.0) |
| Preoperative diagnosis | |
| Chemical/thermal burn | 11 (27.5%) |
| Aniridia | 5 (12.5%) |
| Stevens-Johnson syndrome | 1 (2.5%) |
| Ocular cicatricial pemphigoid | 1 (2.5%) |
| Rheumatoid arthritis | 1 (2.5%) |
| Multiple failed grafts | |
| Keratoconus | 4 (10%) |
| Herpes simplex keratitis | 4 (10%) |
| Corneal dystrophy | 4 (10%) |
| Other | 9 (22.5%) |
Table 2 summarizes the glaucoma variables in our patient group. Twenty-three eyes (57.5%) had preoperative glaucoma, defined as the need for intraocular pressure-lowering medications at the time of surgery or a history of having undergone prior glaucoma filtering procedures, cyclodestructive procedures, or both. Fourteen eyes (35.0%) had prior glaucoma surgery, cyclodestructive procedures, or both; 1 patient had undergone both procedures. Additionally, 3 eyes (7.5%) underwent placement of a glaucoma drainage device concomitantly with placement of the Boston keratoprosthesis. Two of the glaucoma drainage devices placed were placed as stage I Baerveldt glaucoma implants (ie, glaucoma drainage device hardware placed at the time of the surgery but the tube was not hooked up to the anterior or posterior chamber); these stage I shunts had not yet been connected at the last follow-up visit for these 2 patients.
| Eyes with pre-KPro glaucoma | 23 (57.5%) |
| Average no. of preoperative glaucoma medications in patients with glaucoma | 1.50 |
| Eyes with prior glaucoma filtering surgery or CPC | 14 (35.0%) |
| Eyes with prior GDD placement only | 8 (20.0%) |
| Eyes with prior trabeculectomy only | 1 (2.5%) |
| Eyes with both prior trabeculectomy and GDD | 4 (10.0%) |
| Eyes with multiple GDDs | 2 (5.0%) |
| Eyes that had GDDs placed at the time of KPro surgery | 3 (7.5%) |
Table 3 summarizes the development and progression of postoperative glaucoma in our patient group. Long-term complications related to glaucoma drainage devices included 10 tubes in 9 eyes in which glaucoma drainage device erosions developed during the postoperative course ( Table 3 ). The 10 glaucoma drainage device erosions represented 58.8% of all devices that were placed at any given time in this group of 40 patients. Of those devices that eroded, 6 had to be removed.
| Eyes being treated for glaucoma at last follow-up visit | 32 (80.0%) |
| Average no. of glaucoma medications at last follow-up visit for all patients with glaucoma | 1.22 |
| Eyes requiring ECP or CPC during postoperative course | 5 (12.5%) |
| Eyes requiring placement of GDDs during postoperative course | 2 (5.0%) |
| Development of end-stage glaucoma | 7 (17.5 %) |
| Total number of GDDs | 17 |
| Eyes with GDD erosions | 9 (22.5%) |
| Total no. of eroded GDDs (percentage of total devices) | 10 (58.8%) |
| Total no. of GDDs removed (percentage of total devices) | 6 (35.3%) |
Table 4 shows best-corrected visual acuity (BCVA) before and after surgery in eyes in which glaucoma drainage device erosions subsequently developed as compared with eyes with glaucoma drainage devices in which they did not. It also compares preoperative and postoperative BCVA of eyes with and without glaucoma (including those with a glaucoma drainage device) before placement of the keratoprosthesis. Before surgery, BCVA was comparable in all groups. At 1 year, those eyes with a history of preoperative glaucoma already showed a decline in the percentage of eyes that maintained BCVA of 20/200 or better, whereas there was only a minimal change in the BCVA of those eyes without preoperative glaucoma after 1 year. There is a more pronounced difference at the final follow-up visit between these different groups. Eyes with preoperative glaucoma retained BCVA of 20/200 or better in only 45.0% of eyes as compared with those eyes without preoperative glaucoma (62.5%). More importantly, of those eyes in which tube erosions developed, only 25% maintained BCVA of 20/200 or better. In comparison, 60% of eyes with tube shunts without erosions maintained BCVA of 20/200 or better and 62.5% of eyes without preoperative glaucoma maintained that level of visual acuity.
| % of eyes with preoperative visual acuity <20/400 | |
| All eyes without glaucoma (n = 17) | 76.5% |
| All eyes with glaucoma (n = 23) | 82.6% |
| Eyes with GDD without erosions (n = 7) | 100.0% |
| Eyes with GDD erosions (n = 9) | 77.8% |
| % of eyes with BCVA ≥ 20/200 at 1 year follow-up | |
| All eyes without preoperative glaucoma (n = 16) | 75.0% |
| All eyes with preoperative glaucoma (n = 20) | 55.0% |
| Eyes with GDD without erosions (n = 5) | 60.0% |
| Eyes with GDD erosions (n = 8) | 75.0% |
| % of eyes with BCVA ≥ 20/200 at final visit and at least 1 year follow-up | |
| All eyes without preoperative glaucoma (n = 16; follow-up range, 17.9 to 72.0 mos) | 62.5% |
| All eyes with preoperative glaucoma (n = 20; follow-up range, 13.3 to 64.4 mos) | 45.0% |
| Eyes with GDD without erosions (n = 5; follow-up range, 13.3 to 39.3 mos) | 60.0% |
| Eyes with GDD erosions (n = 8; follow-up range, 20.4 to 64.4 mos) | 25.0% |
The clinical courses of the 9 eyes and 10 glaucoma drainage devices in which tube erosions developed are outlined in Table 5 . The duration of the shunt before surgery, preoperative visual acuity, preoperative intraocular pressure, best vision documented after surgery, duration after surgery to tube erosion, subsequent complications related to tube erosion, and final visual acuity at last follow-up visit are documented.
| Patient No. | Underlying Disease | GDD: Type, Location (covered by) | Duration of GDD before Surgery (mos) | Preoperative VA | Preoperative IOP (mm Hg) | Best VA after Surgery (Time Recorded; mos) | Time to GDD Erosion after Surgery (mos) | Complications | Length of Follow-up (mos) | Final VA |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Chemical burn | IT BGI (unknown) | 53 | HM | 32 | 20/150 (3) | 45 | Noted to have a CL fragment near the erosion site during the initial tube revision. Initial tube revision with Tutoplast failed. Subsequent removal of GDD with concomitant ECP. | 64 | HM |
| 2 | Keratoconus with multiple failed PKP | (1) IN Ahmed (unknown) (2) Pars plana ST BGI (unknown) | (1) 10 (2) 19 | HM | 29 | 20/25-2 (6) | 8 | Contact lens eroding the conjunctiva overlying IN Ahmed initially noted but reconjunctivalized spontaneously. Subsequent exposure again 26 mos later with associated drop of VA to HM, removal of IN Ahmed GDD and CPCx2. | 54 | HM |
| 3 | Multiple failed PKP | (1) IN Ahmed (Tutoplast) (2) Pars plana ST BGI (Tutoplast) | (1) 15 (2) 5 | 20/400 | 16 | 20/50 (24) | (1) 30 (2) 32 | Development of Pseudomonas aeruginosa endophthalmitis with concomitant IN Ahmed tube exposure. Revision with Tutoplast followed by choroidal detachment, RD with exposure of second tube 2 mos later requiring removal of ST BGI. IN Ahmed plate exposure 2 mos subsequently requiring removal. | 52 | LP |
| 4 | Keratoconus with multiple failed PKP | ST pars plana BGI (unknown) | 40 | CF | 15 | 20/40 (12) | 17 | Exposure of Hoffman elbow with revision using Tutoplast. Fourteen mos after revision, plate became exposed, requiring second revision. | 44 | 20/50-2 |
| 5 | Multiple failed PKP | ST BGI (unknown) | Placed 17 mos after Kpro | HM | 5 | CF | 2 | Small area of scleromalacia with associated adjacent GDD erosion. Glued to close wound leak. Subsequently pre phthisical and lost to follow-up. | 20 | HM |
| 6 | Aniridia | ST BGI (Tutoplast) | 30 | CF | 17 | 20/20 (3) | 4 | GDD erosion and repair with subsequent endophthalmitis, hypotony, and KPro extrusion. GDD removed at time of endophthalmitis. | 33 | HM |
| 7 | Aniridia | ST BGI (Tutoplast) | 36 | 20/400 | 9 | 20/150 (3) | 9 | GDD removed. Subsequent hypotony, choroidal detachments, and RD. | 27 | NLP |
| 8 | Multiple failed PKP | ST BGI (Tutoplast) | 37 | CF | 21 | 20/30 (3 to 12) | 11 | Erosion occurring at edge of CL. Revised with Tutoplast. | 24 | 20/70-1 |
| 9 | Aniridia | ST pars plana BGI (Tutoplast) | 53 | LP | 10 | HM | 7 | Erosion at anterior edge of Hoffman elbow. Revised/covered with corneal patch. | 9 | HM |
Overall, 9 of 10 glaucoma drainage devices in which tube erosions developed after surgery were placed before placement of the Boston type 1 keratoprosthesis. The average duration that the eroded devices were in place before placement of the keratoprosthesis was 31 months (range, 5 to 53 months). Only 1 tube erosion occurred in a device placed after the keratoprosthesis surgery at postoperative month 17 (Patient 5). The glaucoma drainage devices that were placed at the UC Davis had excellent documentation as to whether the tube was covered at the close of the case and with what material. Six of 10 tubes in this group were known to have been covered with Tutoplast allograft pericardium based on operative reports. The remaining 4 tubes were placed at outside institutions and the operative records were not available. The location (inferior nasally vs superior temporally) and the site of insertion (limbus vs pars plana) also are noted in Table 5 .
The average duration between the placement of the Boston keratoprosthesis and the erosion of the glaucoma drainage device was 16.5 months (range, 2 to 45 months). Visual outcomes after erosion of the glaucoma drainage device were poor, with only 2 eyes maintaining BCVA of 20/200 or better at the final follow-up visit (Patients 4 and 8), despite 7 eyes having attained that level of vision at some point during the postoperative course.
Table 5 also highlights the complications occurring after drainage device erosion, including those in 2 eyes in which endophthalmitis developed at the time of or immediately after the episode of tube erosion (Patients 3 and 6). Patient 3 had culture-positive endophthalmitis secondary to Pseudomonas aeruginosa while receiving routine prophylaxis with fortified vancomycin drops twice daily. In Patient 6, endophthalmitis developed (presumed Staphylococcus aureus ) also while receiving routine prophylaxis with fortified vancomycin drops twice daily. In 3 eyes, hypotony, prephthisis, or both developed after the erosion and repair or removal of the glaucoma drainage device (Patients 5, 6, and 7), and 1 of these eyes subsequently extruded the keratoprosthesis spontaneously (Patient 6). Six of the glaucoma drainage devices had to be removed (Patients 1, 2, 3, 6, and 7), with 2 eyes requiring cyclophotocoagulation procedures to help with intraocular pressure control after glaucoma drainage device removal (Patients 1 and 2).
Table 6 summarizes the remaining 7 eyes with glaucoma drainage devices in which tube erosions did not develop. All of these glaucoma drainage devices were placed at UC Davis, and good records of the operative report were available for review. Only 3 of these devices had been placed before surgery (Patients 11, 12, and 13), with an average duration before surgery of 15.7 months (range, 7 to 27 months). Three devices were placed at the time of keratoprosthesis surgery (Patients 10, 15, and 16), and 1 device was placed after the keratoprosthesis surgery (Patient 14). Two patients (Patients 12 and 15) had stage I Baerveldt devices placed. Five glaucoma drainage devices had Tutoplast placed over the tube. The 2 glaucoma drainage devices that did not have Tutoplast were placed as stage I procedures.
