Erosion of conjunctiva over the suture knot with a leak in an eye with a non-flow restrictive aqueous drainage device

Abstract

We report a case of conjunctival erosion due to ligature suture knot exposure following Aurolab aqueous drainage device (AADI) implantation. A 48-year-old man, a known case of primary angle-closure glaucoma, had failed trabeculectomy with mitomycin-C and Ahmed glaucoma valve (AGV) in the right eye. The right eye had a large posterior AGV bleb with hypertropia and limitation of extraocular movement on downward gaze and uncontrolled intraocular pressure (IOP). An inferonasal AADI was performed uneventfully. At the 1-month postoperative visit, a small conjunctival erosion was noted over the ligature (6-0 vicryl) suture knot. However, there was no leak. Two weeks later, there was hypotony and a leak was noted at the site of the absorbed ligature. Immediate surgical repair was performed by re-ligature of the AADI tube with 8-0 vicryl and the ligature knot was placed under the scleral patch graft and the conjunctival defect was sutured. Early intervention helped in successfully healing the conjunctival erosion, reversal of the hypotony and well-controlled IOP. Adequate covering of the entire subconjunctival tube including its ligated part by a patch graft may prevent this complication.

Background

Non-flow restrictive glaucoma drainage devices (GDDs) are available and are being used increasingly in refractory glaucoma.¹ They have been shown to provide better long-term intraocular pressure (IOP) control compared with flow-restrictive devices.¹ However, the hypotony-related complications can be sight-threatening and are often related to ligature opening in the early postoperative period and plate or tube erosion in the late postoperative period.² Several risk factors for conjunctival and tube erosion have been reported in the literature, the most important being diabetes mellitus, long-term use of antiglaucoma medications (AGMs), multiple previous intraocular surgeries with conjunctival scarring and female gender.² Several mechanisms have been hypothesised, including mechanical trauma of the lids by blinking or eye rubbing, especially in high-risk eyes.²

Donor patch graft or scleral tunnel technique is used to cover the entire length of the subconjunctival tube to prevent conjunctival erosion. To prevent hypotony in the early postoperative period, in eyes with non-valved implants, flow restriction is provided by complete tube ligation using one or two ligatures with 6-0/7-0 vicryl sutures. They are placed with the knots lying posteriorly or sideways to prevent knot exposure. However, the knot may be displaced anteriorly and may erode the conjunctiva when not adequately covered with a patch graft and when the conjunctiva is thin or under traction. We would like to present the consequences of the erosion of the conjunctiva due to knot exposure and its management following implantation of a non-flow restrictive drainage device.

Case presentation

A 48-year-old male was referred to us with uncontrolled IOP in his right eye. He was a known case of primary angle-closure glaucoma in both eyes. His earlier interventions were trabeculectomy with mitomycin-C in both eyes, followed by bleb needling and Ahmed glaucoma valve (AGV) implantation in the right eye. On examination, the best-corrected visual acuity was 20/20, N6 in both eyes. There was hypertropia with −2 limitation of extraocular movement on downward gaze in the right eye. On slit-lamp examination, the right eye was pseudophakic with a posteriorly located large encapsulated bleb, sulcus placed AGV tube at 11 0’clock and surgically patent iridectomy at 12 0’clock. Ultrasound B-scan of the right eye showed posteriorly positioned (beyond 12 mm from the limbus) a large bleb measuring about 13.5×8.7 mm (figure 1A). Slit-lamp examination of the left eye was normal with superior patent surgical iridectomy, well-functioning superior diffuse bleb and pseudophakia. The IOP recorded with Goldmann applanation tonometer in the right eye was 23 mm Hg on maximum medical therapy and in the left eye, IOP was 14 mm Hg on single AGM. On fundus examination, the right showed a tilted disc with cup-disc-ratio of 0.9, and a bipolar notch, while the left eye had early disc damage with 0.7 cup-disc-ratio with superior and inferior equal rims.

Figure 1.

(A) B-scan of the right eye showing posterior positioning of a large bleb covering the Ahmed glaucoma valve plate measuring about 13.5×8.7 mm. (B) Slit-lamp picture of the right eye showing inferonasal placement of Aurolab aqueous drainage device tube in the sulcus, seen through the pupillary area from 5 to 7 o’clock.

Because of uncontrolled IOP, the decision for implanting a second GDD was made and a non-flow restrictive device, the Aurolab aqueous drainage device (AADI) was placed in the inferonasal quadrant. The surgery was performed by a limbal based conjunctival incision. The implant was placed behind the inferior and medial recti muscles and fixed with 9-0 polypropylene sutures. The tube was ligated with two 6-0 vicryl sutures with the knots placed laterally. The tube was placed in the ciliary sulcus through a 4 mm needle track created using a 24G needle, and the tube was fixed to the underlying sclera with a 10-0 nylon suture. Anterior fenestrations were performed on the tube and the tube was covered with a scleral patch graft. The patch graft covered one ligature completely, and the second suture was not covered with a patch graft to allow for suture lysis if required.

Postoperatively, the conjunctival suture line was intact, the tube was well placed in the sulcus (figure 1B). Topical AGMs, soft steroids (Loteprednol Etabonate in tapering doses) and lubricants were continued. Because of the long-term use of topical AGMs and multiple intraocular surgeries, he was started on prophylactic oral doxycyclline 100 mg twice daily for 3 weeks. At the 1-month postoperative visit, there was a small area of conjunctival erosion noted over the area of vicryl ligature knot which stained fluorescein positive but without any leak as shown in figure 2A, B. He was unable to follow-up with us due to travel restrictions imposed during the COVID-19 pandemic and was asked to follow-up with a glaucoma specialist locally. When seen 2 weeks later, the ligature knot had degraded with an active leak from the conjunctival erosion (figure 2C), and the globe was hypotonus with an IOP of 4 mm Hg. There was no choroidal detachment on examination of the fundus.

Figure 2.

(A) Slit-lamp examination of the right eye showing exposed 6-0 vicryl ligature knot through the conjunctiva. (B) The conjunctival defect was taking up the fluorescein stain, but there was no leak noted. (C) Six weeks postoperative period, the slit-lamp picture shows aqueous leak from the conjunctival erosion noted with fluorescein stain. (D) Slit-lamp picture of the right eye 3 weeks post-re-suturing that shows well-healed conjunctiva and adequately covered sclera patch graft.

Investigations

A B-scan of the right eye was performed to see the position and extent of the bleb. This showed posterior positioning of a large bleb measuring about 13.5×8.7 mm.

Treatment

AADI being a non-flow restrictive implant, with the possibility of serious sight-threatening complications due to hypotony, the patient was taken up for immediate surgical repair. The conjunctiva was explored at the area of the leak, and the tube was re-ligated with 8-0 vicryl. The knot was covered with the scleral patch graft and the conjunctiva was sutured with 8-0 vicryl. Two weeks post-re-ligature, the conjunctiva healed well (figure 2D), and 5–6 weeks later the IOP was well controlled when the ligature was absorbed.

Outcome and follow-up

Currently, he is not on any AGM with a well-controlled IOP at 15 mm Hg. However, his right eye (RE) exotropia and hypertropia increased following inferonasal placement of AADI and awaiting its management.

Discussion

The GDDs are used in refractory glaucomas.³ Valved implants have outflow restriction, hence do not require any suture ligation or stenting to resist outflow.³ However, the non-flow restrictive devices do not offer resistance until the bleb around the plate is formed, which offers resistance to outflow after 4–6 weeks. Until this time, tube ligature with or without intraluminal stent resists outflow and prevents hypotony.¹ This ligature suture is performed with a 6-0 or 7-0 vicryl and is well covered with a patch graft to prevent knot exposure.¹ A loose suture may lead to hypotony, hence some surgeons use two ligatures to be cautious. These ligature knots may be exposed by mechanical trauma to the overlying conjunctiva, especially when the conjunctiva is thin and stretched or not adequately mobile.⁴

Our patient had conjunctival erosion over the area of the ligature knot that was not adequately covered by the scleral patch graft. Although there was no leak when the suture was intact, once the suture was absorbed, a leak was noted at the site of erosion which resulted in hypotony. Since this complication was partly anticipated, the patient was followed up closely and was taken up for immediate surgical repair. The conjunctiva was explored in the area of erosion, and re-ligature of the tube was performed. The edge of the conjunctiva was freshened and sutured meticulously. Could this have been managed with only suturing of the conjunctiva is a question? However, in our experience, for the conjunctiva to heal well, the leak has to be stopped and the filtration has to be restricted by tube re-ligature. Although a rare complication, this can occur in predisposed cases that need early identification and appropriate intervention. Care should be taken for meticulous closure of the conjunctiva in eyes with scarred or fibrosed conjunctiva. Adequate dissection of the adjacent conjunctiva to allow traction-free closure and relaxing incision over the forniceal conjunctiva (taking care to leave the tenon’s capsule intact) would allow the tissue to slide anteriorly and allow traction-free closure. Early intervention helped in preventing serious complications like extensive choroidal detachment or suprachoroidal haemorrhage. Although rare, endophthalmitis can also occur as reported in a case with late-onset endophthalmitis 4 years post-non-valved implant with conjunctival buttonhole that occurred due to exposed suture knot securing the implant plate.⁵ Another case report of aqueous tube shunt erosion with signs of infection was managed by a pericardial tissue patch graft covering the tube and a large conjunctival peritomy performed to adequately mobilise conjunctiva for traction-free closure.⁶

Patient’s perspective.

I have been very apprehensive about multiple surgeries. However, I am thankful for the services provided by the timely intervention during the pandemic COVID-19, which has helped me in control of IOP and also prevented serious complications that may have needed explanation of the device as explained by my treating doctor.

Learning points.

• The importance of adequate covering of the tube and the ligature knot in non-valved implants by a patch graft during surgery.

• Always examine the area of the bleb and evaluate the health of the conjunctiva for any signs of tube or plate erosion or predisposition for the same at each postoperative visit. In case of any suspicion or erosion, it has to be managed appropriately.

• Early identification and appropriate intervention will go a long way to prevent the eye from serious implant-related complications.

Ethics statements

Patient consent for publication

Obtained.