Goniosynechialysis Combined with iStent Implantation for Refractory Angle Closure Following Tectonic Penetrating Keratoplasty: A Case Report

Abstract

Aim and background

To report a case in which a targeted early minimally invasive glaucoma surgery (MIGS) approach successfully prevented irreversible sight loss from acute secondary angle closure following tectonic penetrating keratoplasty (PKP) in an eye with a prior porcine-derived corneal stromal implant (Xenia®) as treatment for advanced keratoconus.

Case description

The authors describe successful surgical treatment of a patient who developed acute intraocular pressure (IOP) elevation following tectonic PKP for perforated bacterial microbial keratitis. We demonstrate that combined goniosynechialysis (GSL) and iStent Inject® trabecular micro-bypass implantation are effective in reversing postoperative synechial angle closure, restoring angle integrity, and preventing progressive glaucomatous optic neuropathy and, thus, irreversible sight loss in an eye with a functioning PKP.

Conclusion

The authors highlight the importance of early recognition and referral to a glaucoma specialist for prompt mechanism-targeted MIGS to manage postkeratoplasty secondary angle closure.

Clinical significance

Early targeted MIGS intervention may prevent the need for complex glaucoma filtration surgery in eyes with secondary synechial angle closure following corneal transplant surgery.

Introduction

Tectonic penetrating keratoplasty (PKP) is a useful therapeutic option in selected cases of corneal thinning and perforation as a result of infection, immunologic causes, or trauma. Prognosis is poor, with high failure rates due to risk factors such as active corneal inflammation, peripheral grafts, lid disease, and larger donor and recipient graft sizes.¹ One of the major complications of tectonic PKP is the formation of peripheral anterior synechiae (PAS) and secondary angle closure, with reported rates ranging from 9.76 to 41.8%.^2,3 Due to active inflammation and comorbidities, PAS formation following tectonic PKP can be aggressive and rapidly lead to acute or subacute angle closure that warrants major interventional glaucoma filtration surgery. Traditionally, this would be in the form of glaucoma drainage device (GDD) implantation with or without prior transscleral cyclophotocoagulation.

Both of these options are highly proinflammatory and do not directly address the mechanisms of angle closure compared to a targeted minimally invasive glaucoma surgery (MIGS) approach. GDD implantation has been shown to increase the risk of tectonic PKP failure and necessitates close early postoperative follow-up due to its higher-risk profile.⁴ There is also the long-term risk of endothelial cell loss, GDD exposure, and infection. Transscleral cyclophotocoagulation also carries a significant risk of PKP failure and the additional risk of chronic sight-threatening hypotony.⁵ Goniosynechialysis (GSL) has been described as an effective treatment for PAS formation after posterior segment surgeries such as vitrectomy and is a common technique in primary angle-closure glaucoma surgery.^6,7 Office-based argon laser treatment for postoperative sectoral iridocorneal adhesion has also been previously described, but there are limited reports in the published literature on the effectiveness of a targeted MIGS approach in treating acute synechial angle closure following keratoplasties.⁸

Case Description

A 27-year-old myopic Caucasian female underwent emergency tectonic PKP for perforated microbial keratitis following a novel porcine-derived intrastromal implant (Xenia, Gebauer Medizintechnik GmbH, Neuhausen, DE) for advanced keratoconus. One week postoperatively, she developed raised intraocular pressure (IOP) as measured with Goldmann applanation tonometry (38 mm Hg) and was commenced on maximal medical treatment before an early glaucoma referral was sought.

Initial glaucoma examination at 8 weeks post-PKP showed a clear graft with intact sutures. The best-corrected Snellen visual acuity (BCVA) was 6/24 in the affected eye, with an IOP of 22 mm Hg. The anterior chamber was deep centrally, and there was no intraocular inflammation. Gonioscopy revealed 360° of synechial angle closure, with low-lying PAS in the nasal quadrant and broad high PAS superiorly and inferotemporally. She was noted to have early lens opacities and a normal cup-to-disk ratio of 0.3 with a healthy neuroretinal rim. Optical coherence tomography (OCT) imaging confirmed a healthy retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) in this eye. Antiglaucoma medications at this point were topical preservative-free latanoprost 50 µg/mL, topical preservative-free fixed-combination dorzolamide 20 mg/mL + timolol 5 mg/mL, and oral acetazolamide 250 mg three times a day. The IOP rose to 46 mm Hg the following week after the patient discontinued oral acetazolamide due to systemic side effects.

A diagnosis of secondary synechial angle closure was made, and the patient underwent urgent phakic GSL with iStent Inject® implantation under direct visualization using a surgical gonioprism (Swan Jacob, Ocular Instruments®, Washington, USA) and 25-gauge micrograsping forceps (MicroSurgical Technology, Redmond, USA) under sub-Tenon local anesthesia. After making a three-stepped paracentesis using a 20-gauge microvitreoretinal blade, the anterior chamber was initially deepened with a cohesive viscoelastic device (Healon GVTM Pro) to create space and attempt to release some of the high PAS. The micrograsping forceps were then utilized to carefully and gently release all the PAS without causing excessive bleeding from the angle until the scleral spur was visualized (Figs 1A to C). An iStent Inject® trabecular micro-bypass implant was placed through the nasal pigmented trabecular meshwork after 360° of GSL had been performed to relieve the widespread PAS (Fig. 1D). Good reflux of blood from the canal of Schlemm through the iStent Inject® and into the anterior chamber was observed intraoperatively and confirmed adequate implant placement. Intracameral dexamethasone (0.2 mL of 3.3 mg/mL solution for injection, Hameln Pharma GmbH, 31787 Hameln, Germany) and orbital floor triamcinolone (1 mL of 40 mg/mL KenalogTM, Bristol Myers Squibb) were administered at the end of surgery to minimize the inflammatory response.

Figs 1A to D.

Preintervention intraoperative photograph showing diffuse broad PAS viewed using a direct goniolens (A). Intraoperative gonioscopic photograph showing surgical release of the PAS using micrograsping forceps to carefully pull the adherent iris tissue away from the angle (B), with some bleeding from the angle observed (C). Intraoperative gonioscopic photograph showing placement of an iStent Inject® implant through the trabecular meshwork after the PAS were released from the trabecular meshwork (D)

At postoperative day one, the BCVA was 6/36, with an IOP of 26 mm Hg but without the need for any antiglaucoma medications. The anterior chamber was deep, and the angle was open to the level of the ciliary body band as examined on gonioscopy. There was significant postoperative inflammation and fibrin, which responded well to intense long-term topical steroid (preservative-free dexamethasone 0.1%) use.

At 48 months' follow-up, BCVA was 6/6 (6/9 unaided) in the affected eye following phacoemulsification cataract extraction and intraocular lens implantation at the 16-month time point. The tectonic PKP remained clear, with corneal sutures in situ (Fig. 2A). The patient maintained a normal IOP without the use of any antiglaucoma medications throughout the entire postoperative period (Fig. 3).

Figs 2A to D.

Postintervention slit-lamp photograph showing a clear and functioning tectonic PKP 32 months after the glaucoma surgery (A). Slit-lamp gonioscopic view at 32 months postintervention showing good patency and placement of the iStent Inject® with no reformation of the PAS (B). Optical coherence tomography (OCT) images demonstrating no structural glaucomatous damage on the retinal nerve fiber layer (RNFL) and macular ganglion cell complex (GCC) scans (C and D, respectively)

Fig. 3.

Postintervention IOP control vs time; IOP (mm Hg), IOP measured with Goldmann applanation tonometry; NGM, number of topical antiglaucoma medications

Gonioscopy demonstrated open angles with good patency and positioning of the iStent Inject® implant without PAS reformation at the 32-month time point (Fig. 2B). The corneal graft remained clear, with both RNFL and GCC OCT imaging demonstrating no structural evidence of glaucomatous damage (Figs 2C to D). The patient remains on long-term once-daily dosing of topical preservative-free dexamethasone 0.1% alone and continues to be monitored regularly in the cornea service.

Discussion

To the best of the authors' knowledge, this represents one of the first reported cases of GSL combined with iStent Inject® implantation for treating secondary angle closure due to acute PAS following tectonic PKP. There are a number of mechanisms of PAS development in such cases. When tectonic PKP is performed as a therapeutic treatment secondary to a perforated corneal ulcer, a larger graft size is usually selected, and consensus is to remove at least 1 mm of healthy corneal tissue in order to provide a stable recipient bed with the aim of salvaging an eye that might otherwise have been lost.⁹ However, a larger graft size increases the risk of iris incarceration and, therefore, PAS formation during corneal graft suturing to host tissue. Secondly, such cases of infected corneal ulcers often generate an intense inflammatory reaction that has also been thought to contribute to the rapid development of PAS and subsequent secondary angle closure.¹⁰ In the present case, targeted GSL was able to release all the PAS to enable restoration of normal angle anatomy and provide normal trabecular outflow access for the aqueous.

Although it is possible that GSL alone may have sufficed for initial IOP control, the iStent Inject® was implanted in addition for two reasons. First, it was not known whether lasting trabecular dysfunction had already ensued following 8 weeks of synechial angle closure and, if so, GSL alone may not have been sufficient to achieve IOP control. Second, it would preempt a potential future steroid-induced open-angle glaucoma, given that the patient would need to be on long-term topical steroids and was already at greater risk of a steroid response because of her preexisting myopia. This prophylactic surgical approach therefore addressed the current and potential future issues with the patient's IOP control in a minimally invasive manner. We do, however, acknowledge that the additive value of the iStent Inject® when utilized in this prophylactic and adjunctive manner cannot be determined from a single case.

One could also have utilized an implant-free trabecular bypass procedure such as Kahook Dual-Blade® goniotomy, gonioscopy-assisted transluminal trabeculotomy (using iTrack™ or OMNI®), or excimer laser trabeculostomy (using ELIOS™) for the same reasons. Theoretically, these may have been even better for the survival of the tectonic PKP by having a lesser impact on the corneal endothelial cell loss rate postoperatively. The authors did not, however, have access to these implant-free MIGS alternatives and therefore felt that the iStent Inject® was the safest available MIGS option for the desired aim of avoiding transscleral cyclophotocoagulation or GDD implantation and their respective greater-risk profiles.

Conclusion

In conclusion, the authors demonstrate that a timely MIGS approach in the form of targeted GSL combined with iStent Inject® trabecular micro-bypass implantation following tectonic PKP can successfully reverse secondary synechial angle closure, restore angle integrity, and prevent progression to glaucomatous optic neuropathy and, thus, irreversible sight loss without compromising the survival of a PKP. In this case, early glaucoma input also meant a minimal duration of cornea-toxic topical antiglaucoma medications, which is also likely to have helped the long-term survival of the keratoplasty.

Clinical Significance

This case highlights the importance of timely mechanism-targeted MIGS in keratoplasty patients in order to directly address the secondary causes of raised IOP and obviate the need for glaucoma filtration surgery altogether.

Acknowledgment

Nil.

Author's Contribution

UK contributed to data collection, writing of the manuscript, and data analysis. AAM contributed to the conceptualisation of, reviewing of and editing of the manuscript, methodology, supervision, and data analysis. LJ contributed to data collection, reviewing of and editing the manuscript. BI contributed to the methodology, reviewing of the manuscript and supervision.

AI Disclosure

The authors declare that no artificial intelligence (AI) tools, large language models (LLMs), or AI-assisted technologies were used in the generation, writing, or editing of this manuscript.

Orcid

Abhijit A Mohite https://orcid.org/0000-0002-9270-136X