Partial-Thickness Corneal Patch Graft with Fibrin Glue for Tube Shunt Exposure: Case Report

Abstract

Introduction

Tube exposure is a serious complication of glaucoma drainage device implantation. We describe a novel surgical approach using a partial-thickness corneal patch graft with conjunctival autograft and fibrin glue in a setting of severe conjunctival deficiency.

Case Presentation

We describe a 72-year-old man with chronic angle-closure glaucoma who presented with tube exposure 1 year after Ahmed valve implantation. Risk factors included diabetes mellitus, a failed trabeculectomy, and prior vitrectomy. The conjunctiva surrounding the exposed tube was ischemic and immobile, and the original corneal patch graft had partially degraded. Revision surgery involved suturing a 4-mm partial-thickness corneal button over the exposed tube, anchored to the residual graft edge and sclera. Due to insufficient mobile conjunctiva, a 4 × 3 mm conjunctival autograft was harvested from the temporal bulbar conjunctiva and secured with fibrin glue at the border of the corneal button, partially covering it, to promote epithelialization. At 1-year follow-up, the tube remained fully covered with no recurrence.

Conclusion

This unique surgical approach using a partial-thickness corneal button and conjunctival autograft offers a viable alternative in cases of tube exposure with severe conjunctival deficiency, where traditional techniques such as conjunctival advancement are not feasible.

Introduction

Glaucoma drainage devices have become a cornerstone in managing refractory glaucoma, particularly in complex cases or when trabeculectomy has failed [1]. In order to prevent erosion of the tube through the conjunctiva, it is commonly covered with a patch graft – which can be made of several materials including processed pericardium, sclera, fascia lata, dura, and cornea [2]. Nevertheless, tube exposure remains a known complication. In the Ahmed Baerveldt Comparison study [3], the incidence of tube exposure at 5 years was 1% and 3% in the Ahmed glaucoma valve and Baerveldt glaucoma implant groups, respectively. In the TVT study [4], the total incidence of exposure in the tube shunt group was 5%.

Tube exposure is associated with a significantly increased risk of endophthalmitis [3], necessitating urgent surgical repair. Risk factors for tube exposure include female gender, white race, older age, diabetes mellitus, ocular inflammation, previous conjunctival surgery, and inferior tube placement [5, 6]. Mitomycin C exposure from prior trabeculectomy may also contribute to conjunctival immobility and ischemia. Repair of tube exposure depends on several factors including the presence of infection, device functionality, and the condition of the surrounding tissue. Surgical repair options include complete removal of the implant (e.g., in cases of major plate exposure), tube repositioning (such as sulcus or pars plana placement), and patch grafting with different materials. Secondary patch grafts are crucial, as their use significantly reduces reexposure risk [7]. Closure options vary depending on conjunctival availability and include conjunctival advancement, conjunctival autografts, forniceal pedicle flaps, buccal mucosal grafts, amniotic membrane, or synthetic materials. Each technique must be adapted to the degree of tissue loss and the overall ocular condition [8–10].

In challenging cases where conjunctival integrity is compromised, achieving watertight coverage becomes particularly difficult. Wide tissue dissection may be required to mobilize sufficient conjunctiva and avoid tension at the limbus during closure. Moreover, the use of secondary patch grafts plays a key role in minimizing the risk of recurrent exposure. As secondary patch grafts are crucial in minimizing the risk of recurrent exposure, some surgeons also prefer to alternate the graft material when the first patch has eroded (e.g., using cornea after sclera, or sclera after cornea). The following case describes a challenging instance of tube exposure in a high-risk patient, showing the surgical difficulties and the customized approach needed when the surrounding conjunctiva is scarred or immobile.

Case Presentation

A 72-year-old man with a history of diabetes mellitus, systemic hypertension, and chronic obstructive pulmonary disease presented with tube exposure in the right eye. He had been followed for chronic angle-closure glaucoma and previously underwent bilateral laser peripheral iridotomy, followed by cataract surgery in both eyes. He also had retinal vein occlusion in the right eye, treated with monthly intravitreal aflibercept injections and pars plana vitrectomy due to secondary epiretinal membrane.

The patient initially underwent trabeculectomy due to uncontrolled glaucoma, followed by Ahmed glaucoma valve implantation in the superotemporal quadrant. One year postoperatively, he presented with tube exposure approximately 2 mm posterior to the limbus, with surrounding ischemic and scarred conjunctiva.

Surgical Technique

Revision surgery was performed 3 days after tube exposure was noted (video is attached as online suppl. material; for all online suppl. material, see https://doi.org/10.1159/000548727). Intraoperatively, the conjunctiva was found to be immobile and scarred, and the previously placed corneal patch graft had partially melted. A 4-mm trephination was performed over the area of tube exposure, and a new partial-thickness corneal button was prepared from a residual donor corneal rim following Descemet Stripping Automated Endothelial Keratoplasty preparation. The anterior lamella was separated manually to create a tectonically stable partial button [11]. The button was sutured over the exposed tube using interrupted 10-0 nylon sutures, anchored to both the residual graft margin and the underlying sclera.

Due to extensive ischemia, adjacent conjunctiva could not be advanced for closure. Instead, a 4 × 3 mm conjunctival autograft was harvested from the temporal bulbar conjunctiva and secured using fibrin glue at the border of the corneal button, partially covering it. This placement enabled vascularization from adjacent conjunctiva, which promoted graft survival and subsequent reepithelialization across the corneal button (shown in Fig. 1). At 2-year follow-up, the tube remained fully covered without any signs of recurrent exposure (shown in Fig. 2).

Fig. 1.

Tube shunt revision using partial-thickness corneal patch graft. a Tube exposure is noted approximately 2 mm posterior to the limbus with surrounding ischemic and immobile conjunctiva (black arrow). b A 4-mm partial-thickness corneal button is sutured over the exposed tube using interrupted 10-0 nylon sutures, anchored to the residual graft edge and underlying sclera. c Conjunctival autograft (4 × 3 mm) is excised from the temporal bulbar conjunctiva (red arrow). d The conjunctival autograft is placed over the corneal graft and secured with fibrin glue (red arrows), providing complete tube coverage.

Fig. 2.

One-year postoperative follow-up. Slit-lamp photograph demonstrating stable tube coverage with well-integrated corneal button and conjunctival autograft. No signs of recurrent exposure or conjunctival breakdown are observed.

Discussion

Tube exposure following glaucoma drainage device implantation is a serious complication, associated with a significantly increased risk of endophthalmitis [3]. Surgical revision is required to restore coverage, but achieving durable and watertight closure can be especially challenging in the presence of conjunctival scarring or ischemia.

In this case, the patient had multiple known risk factors for tube exposure, including diabetes mellitus, advanced age, intravitreal anti-VEGF injections, a history of failed trabeculectomy with mitomycin C, and pars plana vitrectomy. Intraoperatively, the conjunctiva was immobile and ischemic, and the previously placed patch graft had partially degraded. These findings necessitated a creative surgical approach.

Although the use of corneal patch grafts for the repair of exposed glaucoma drainage implants has been previously described, reports remain limited. Singh et al. [12] reported successful outcomes using full-thickness corneal patch grafts to cover exposed glaucoma drainage implant tubes, with good long-term tectonic stability. However, their technique required complete conjunctival coverage over the corneal graft – by either advancement or free graft – and did not involve the use of fibrin glue or partial-thickness corneal buttons. Other authors have described the use of stromal lenticules obtained by small incision lenticule extraction surgery as partial-thickness patch grafts for similar purposes [13].

In contrast, our modified approach is specifically tailored to cases with severe tissue deficiency, with use of fibrin glue to secure a small conjunctival autograft over the corneal patch graft border, allowing vascular ingrowth and subsequent reepithelialization across the graft surface. While the use of conjunctival autografts is not novel and has been previously described for the repair of glaucoma drainage device exposure (e.g., interpolated conjunctival pedicle flaps) [14], its combination with a partial-thickness corneal button in this context has not been reported to our knowledge. Additionally, the use of fibrin glue in this setting has not, to the best of our knowledge, been previously documented.

At 2-year follow-up, the tube remained fully covered, supporting the long-term durability of this technique. While larger studies are needed, this case demonstrates that using a corneal button and autologous conjunctiva can provide effective and lasting tube coverage, even in high-risk settings.

Statement of Ethics

This case report was reviewed and granted exemption from ethics approval by the Institutional Review Board of Tel Aviv Medical Center, in accordance with institutional policy for single-case reports that do not contain identifying information. Written informed consent was obtained from the patient for publication of the details of their medical case and any accompanying images. The CARE Checklist has been completed by the authors for this case report, attached as online supplementary material.

Conflict of Interest Statement

Prof. Shimon Kurtz was a member of the journal’s Editorial Board at the time of submission. The rest of the authors have no conflicts of interest to declare.

Funding Sources

This study was not supported by any sponsor or funder.

Author Contributions

M.N. contributed to data collection and manuscript writing and editing, and coordinated the submission process. D.R. contributed to data collection and manuscript writing. D.V., S.K., and M.W. performed the surgical procedure and contributed to critical revision of the manuscript. M.W. additionally provided supervision and guidance throughout the project. All authors reviewed and approved the final version of the manuscript and agreed to be accountable for all aspects of the work.

Funding Statement

This study was not supported by any sponsor or funder.

Data Availability Statement

All data generated or analyzed during this case report are included in this article and its online supplementary material files. Further inquiries can be directed to the corresponding author.