CASE PRESENTATION
A 27-year-old Hispanic man with long-standing,
poorly controlled type 1 diabetes mellitus was referred
to the Montefiore Medical Center Glaucoma Service in
Bronx, New York, for an evaluation of elevated IOP in
his right eye. He complained of severe pain with dimming
vision in this, his only seeing eye.
The patient's past ocular history in his right eye was significant for severe proliferative diabetic retinopathy, with a history of multiple sessions of intravitreal antivascular endothelial growth factor therapy and panretinal photocoagulation (Figure 1). At the time of presentation, his visual acuity was 20/400 OD and no light perception OS. His IOP was 34 mm Hg OD and 12 mm Hg OS. In addition to taking generic acetazolamide 500 mg by mouth b.i.d., the patient was instilling travoprost 0.004% qhs (Travatan Z; Alcon Laboratories, Inc.), brimonidine 0.1% b.i.d. (Alphagan P; Allergan, Inc.), and a fixed combination of dorzolamide HCL 2% and timolol maleate 0.5% b.i.d. (Cosopt; Merck & Co., Inc.) in his right eye.
A slit-lamp examination of the patient's right eye revealed no rubeosis but mild changes to the posterior subcapsular lens. The angle was synechially closed on gonioscopy, but there was no active neovascularization. A dilated examination revealed an old vitreous hemorrhage, an extremely ischemic fundus with regressing neovascularization, and extensive scarring from panretinal photocoagulation in the retina. The optic nerve showed severe pallor, and confrontational visual fields demonstrated peripheral constriction of the visual field to approximately 20º centrally.
The patient was diagnosed with chronic angle closure secondary to neovascular glaucoma, with quiescent proliferative diabetic retinopathy in his right eye.
HOW WOULD YOU PROCEED?
• Would you continue to treat the patient medically or
opt for a surgical procedure? If you chose the latter, what
procedure would you perform?
• What clinical findings would guide your choice of surgical
intervention?
• Would the patient's young age and monocular status
affect your choice and/or the urgency of intervention?
SURGICAL COURSE
Given this monocular patient's IOP of 34 mm Hg on
maximum tolerated medical therapy and clinical presentation with neovascular glaucoma, we decided to
implant a glaucoma drainage device. We implanted an
Ahmed Glaucoma Valve (New World Medical, Inc.,
Rancho Cucamonga, CA) and placed a Tutoplast pericardium
patch graft (IOP, Inc., Costa Mesa, CA) in the
superotemporal quadrant. We secured the patch graft to
the sclera at the limbus with a 7–0 Vicryl suture (Ethicon,
Inc., Somerville, NJ). Intraoperatively, the conjunctival tissue
was noted to be quite friable. The tube's placement
in the anterior chamber was deemed to be appropriate,
and the conjunctiva was closed without excessive tension.
No antimetabolite or cryotherapy was used during
the surgery.
The patient's IOP was 5 mm Hg OD on the first postoperative day and never exceeded 14 mm Hg over the course of the next 1 to 2 months. Three months after the surgery, the patient presented to the Emergency Department with a complaint of severe pain, foreign body sensation, and photophobia in his right eye. The BCVA was 20/400, and the IOP measured 13 mm Hg OD. On slit-lamp examination, the pericardial patch graft was not visible, and approximately 5 mm of the tube was exposed. The exposure started 3 mm from the limbus and extended posteriorly 1 to 2 mm anterior to the plate. The tube was well positioned in the anterior chamber, with no anterior chamber reaction or hypopyon. The bleb was elevated over the plate in the superotemporal quadrant without ischemia or injection.
Given the risk of endophthalmitis, the patient was started immediately on topical moxifloxacin 0.5% q2h (Vigamox; Alcon Laboratories, Inc.) and taken to the OR the following morning for a revision of the Ahmed Glaucoma Valve. We resected the conjunctival tissue around the site of erosion and placed amniotic membrane (Amniograft-G; Bio-Tissue, Inc., Miami, FL) over the tube. Conjunctival/Tenon's advancement was performed to cover the membrane and tube adequately, but the conjunctiva was noted to be under greater tension than after the primary surgery.
The patient's postoperative course was uneventful until approximately 3 months later, when extensive exposure of the tube in the same location was observed at a routine follow-up visit. The patient restarted Vigamox therapy q2h in his right eye and was taken back to the OR on the following day. After again resecting the conjunctival tissue, we placed a Tutoplast scleral patch graft (IOP, Inc.) over the tube. The conjunctival tissue was extremely friable, and we could not adequately cover the tube with a scleral patch graft using standard techniques. Given the patient's young age and potential need for future tube shunt surgery, we decided to leave as much intrinsic conjunctival tissue intact as possible in his right eye. A large 10 X 10-mm conjunctival graft was harvested from his blind left eye and transplanted to cover the tube in his right eye (Figure 2). The conjunctival graft was sutured in place with minimal tension over the scleral patch graft with a 10–0 Vicryl suture.
Fifteen months after the last revision, the patient's BCVA remains 20/400 OD, with the IOP ranging from 12 to 16 mm Hg off all glaucoma medications. During this period, he has received three intravitreal injections of antivascular endothelial growth factor and fill-in panretinal photocoagulation for his proliferative diabetic retinopathy. The tube remains covered with the contralateral eye conjunctival autologous graft, but the scleral patch graft has melted significantly during the past year (Figure 3).
DISCUSSION
As reported in retrospective reviews of glaucoma
drainage device implantation, the incidence of tubal erosion
ranges from 0% to 16%, with no association with
implant model.1-5 In a retrospective comparative series of
patients undergoing drainage device surgery that compared
single-thickness to double-thickness pericardium
grafts, Lankaranian et al showed a significantly lower rate
of erosion at 9 months, which was 16% (5/31) versus 0%
(0/59) in the double-thickness group. In a recent metaanalysis
by Stewart et al of more than 3,000 eyes receiving drainage devices, the incidence of conjunctival erosion
was 2.0% at an average of 26 months' follow-up.2 Further
subgroup analysis is warranted to determine the relative
risk of erosion for each particular type of glaucoma,
because it is likely that eyes that are more prone to
chronic inflammation and tissue friability are at higher
risk of this type of complication.
Our patient suffered multiple erosions, and his longterm prognosis remains guarded at best given his young age, monocular status, and advanced proliferative disease. His options included an interpolated pedicle graft from the superonasal or temporal conjunctiva,6 a free conjunctival graft, buccal mucosal graft,7 fascia lata graft,8 amniotic membrane, hinged scleral graft,9 scleral tunnel,10 or tubal extension with rerouting of the tube to a more superior location. Removal of the primary tube and inferonasal placement of a new implant will always remain an option for this patient. Godfrey et al advocated interpolated pedicle flaps in a case review of four patients with recurrent tubal erosions.6 The advantage of this technique is it maintains the vascular supply to the conjunctival graft. Our technique of a free conjunctival autograft from the contralateral eye in this case had the advantage of sparing conjunctival tissue in the patient's remaining seeing eye; this is of particular importance when future glaucoma drainage implant surgery is likely. Given the amount of prior surgical manipulation superotemporally, future interventions in this quadrant will likely be at higher risk of failure. Extension and repositioning of the tube to a more superior location will likely be our next step if further erosion occurs, assuming that the IOP remains controlled with the primary implant.
Anurag Shrivastava, MD, is an assistant professor in the Department of Ophthalmology at Albert Einstein Medical College, Bronx, New York. He acknowledged no financial interest in the products or companies mentioned herein. Dr. Shrivastava may be reached at (718) 920-5562; ashrivas@montefiore.org.
Jeffrey S. Schultz, MD, is an associate professor in the Department of Ophthalmology & Visual Sciences at Montefiore Medical Center, Bronx, New York. He acknowledged no financial interest in the products or companies mentioned herein. Dr. Schultz may be reached at (718) 920-5562; jschultz@montefiore.org.
