Spontaneous onset pseudophakic malignant glaucoma secondary to zonular weakness and cilio-lenticular block.

Malignant glaucoma (MG), also known as aqueous misdirection and cilio-vitreo-lenticular block, is an infrequent cause of secondary angle closure glaucoma. Despite conventional treatment, it often has a poor visual outcome. It is recognized clinically by raised intraocular pressure associated with shallowing of the peripheral and central anterior chamber in the presence of a patent peripheral iridotomy/iridectomy. Despite being known to occur after a variety of surgical procedures, it most commonly presents following filtration surgery in hypermetropic eyes with angle closure glaucoma. It can present within a range of postsurgical latencies, ranging from 1 day to many months. We describe a case of pseudophakic MG that was unusual in that it presented spontaneously many years following cataract surgery. We postulate the etiology of our spontaneous onset pseudophakic MG was the anterior subluxation of the large diameter intraocular lens secondary to zonular weakness.

Introduction

Malignant glaucoma (MG) is rare, secondary angle-closure glaucoma. The term, introduced by Von Graefe, describes a condition that worsened despite conventional therapy, with poor visual outcome.[1] It's recognized by raised intraocular pressure (IOP), flattening of the central and peripheral anterior chamber (AC), patent peripheral iridectomy/iridotomy (PI) and the absence of suprachoroidal haemorrhage/effusion. IOP may remain normal initially; the first symptom being improved near vision from myopic shift. It mostly occurs following filtration surgery in hypermetropic eyes,[2] but can follow laser iridotomy/capsulotomy,[3] cyclophotocoagulation,[4] and cataract surgery.[5] Management is challenging, medical therapy forming the mainstay of initial treatment, achieving resolution within 4–5 days in 50%. Patients often require long-term medications.[6]

We describe an unusual case, presenting spontaneously years following cataract surgery.

Case Report

A 70-year-old with no history of glaucoma or previous trabeculectomy, was referred to the vitreo-retinal clinic with MG. She had routine bilateral cataract surgery 16-year previously. Medical treatment for 2 weeks prior referral with per oral acetazolamide 250 mg QDS, IV mannitol, G travatan, iopidine 1%, timolol 0.25%, cyclopentolate 1% and maxidex failed to reduce the IOP or deepen the AC. YAG laser PI had been performed. She presented with a history of a red, painful right eye. Unaided LogMAR visual acuities were 1.38 and 0.06 in the right and left eyes respectively, with myopic shift in the right. Her right eye had a patent PI, a diffusely shallow AC, no iris bombe or pupil block. The intraocular lens (IOL) was displaced anteriorly, with corneal-endothelial contact [Figure 1], with inferior subluxation. IOP was 26 and 12 mmHg in the right and left eyes, respectively. The cornea remained clear. Ultrasound biomicroscopy ruled out choroidal effusion/hemorrhage, demonstrating anterior rotation of the ciliary body. The retina was flat. The IOL optic was noted to be of large diameter, with no visible peripheral margins. Laser posterior capsulotomy and hyaloidotomy would have been difficult to perform peripheral to the optic. It was felt unlikely a central posterior capsulotomy would result in free flow of aqueous into the AC.

Figure 1

Color photograph of right eye showing shallowing of the peripheral and central anterior chamber. There is anterior displacement of the iris and the intraocular lens implant

Standard 20-gauge pars plana vitrectomy (PPV) with transcleral cyclodiode laser was performed. During core vitrectomy, the AC deepened and was reformed using viscoelastic. Zonular weakness became apparent, with dehiscence and IOL subluxation. On IOL repositioning, complete 360° zonular dehiscence occurred, with the IOL dropping posteriorly. This one-piece lens had a very large diameter optic and was removed with heavy liquid. The patient was left temporarily aphakic. Ten weeks postoperatively the AC was deep, with normal IOP's [Figure 2].

Figure 2

Color photograph of right eye post pars-plana vitrectomy and removal of intraocular lens. The anterior chamber is now deep

Discussion

Spontaneous onset MG is rare, with less than a handful of cases.[78] MG is an infrequent complication of surgery for primary angle-closure glaucomas, occurring in phakic, pseudophakic, or aphakic eyes. MG can present within various postoperative latencies, mostly in the immediate postoperative period. It may present many years later.[9] This case is unusual given its spontaneous onset, 16 years following cataract surgery.

Mechanisms for MG remain unclear, but are likely multifactorial, occurring in eyes with anatomical predispositions, including short axial length. The final pathway is anterior displacement of the ciliary body, iris and lens-diaphragm. Shaffer and Hoskins suggested posterior aqueous flow and accumulation behind the anterior hyaloid is responsible for establishing a one-way valve, creating positive vitreous pressure.[10] Quigley et al. proposed increase vitreous pressure secondary to choroidal expansion.[11] Exact mechanisms remain unexplained.

We postulate the etiology was anterior subluxation of the large diameter IOL secondary to zonular weakness; an association first suggested by Chandler.[12] Miotics have been implicated in precipitation or worsening of MG through similar mechanisms of ciliary muscle contraction, zonular loosening, and anterior lens displacement.[13] In this case, zonular weakness was manifest by lens subluxation and drop, following minimal manipulation and no posterior capsule contact during vitrectomy. We suggest a threshold level of weakness was reached, allowing IOL displacement anteriorly, sufficient to create a direct lens-block. This case represents the longest reported delay for the onset of MG, 16-year following surgery.

Zonular weakness secondary to pseudoexfoliation is a known association of MG.[14] Our patient had no history of pseudoexfoliation or glaucoma. We acknowledge pseudoexfoliative deposits are infrequently found in pseudophakic eyes, but examination revealed no evidence on the IOL. The contralateral trabecular meshwork was not excessively pigmented.

An intact hyaloid face plays an important role in MG; its disruption forms a key part in management. In pseudophakic/aphakic eyes, Nd: YAG-laser capsulotomy and purposeful anterior vitreous disruption may resolve aqueous misdirection.[15] In cases with large diameter optics, aqueous flow into the AC can be difficult to re-establish. Some authors advocate performing capsulotomies through lens dialing holes if present.[16] Given the failure of medical therapy, a definitive surgical option was undertaken.

Success of PPV for managing MG varies depending on lens status. Byrnes et al. reported persistence or recurrence in 50% (5 of 10) of phakic eyes and 10% (1 in 10) pseudophakic eyes.[17] Sharma et al. described success of vitrectomy – phacoemulsification-plus vitrectomy in 5 cases for the management of MG in phakic individuals.[18] Surgical success disparity reflects difficulty disrupting the anterior hyaloid face behind the crystalline lens, without inadvertent lens touch. Techniques to assist disruption include intraocular video-endoscope-guided and fluorescein-assisted PPV.[19] In the main-stay, adequate management of MG in phakic individuals invariably requires the combination of phacoemulsification with vitrectomy, posterior capsulotomy, and subsequent IOL implant. Staged approaches, with initial vitrectomy to soften the eye, deepening the AC are advocated, overcoming difficulties associated with performing phacoemulsification in eyes with shallow AC's and raised IOP.[18] After lens removal and IOL implantation, residual vitrectomy with disruption of the anterior hyaloid and posterior capsule should be performed. Some authors recommend the additional step of a hyaloido-zonulectomy.[20]

Recurrence in pseudophakic individuals could represent inadequate disruption of the anterior hyaloid. We suggest caution in individuals with known zonular weakness and large diameter optic posterior chamber lenses, postulating these could pose potential risk of recurrence through direct cilio-lenticular block secondary to an anteriorly displaced lens.

This case demonstrates MG can occur following significant delay in patients with zonular weakness, highlighting the need to consider IOL optic size, as this may play a significant role in the pathogenesis of aqueous misdirection through direct cilio-lenticular block when combined with zonular weakness. Such cases may require removal of the IOL to prevent recurrence.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.