Pars Plana Tube Insertion of Aqueous Shunt With Vitrectomy in Malignant Glaucoma

Medical treatment, laser surgery, and vitreous surgery have been useful options to treat aqueous misdirection (malignant glaucoma). Two patients with pseudophakic malignant glaucoma unresponsive to medical treatment underwent pars plana vitrectomy and tube shunt implantation through the pars plana. The outcome was favorable in both patients. The implantation of the tube shunt through pars plana can help prevent recurrence of this condition by avoiding reaccumulation of fluid in the posterior segment of the eye, and can help in long-term control of intraocular pressure (IOP) in these glaucomatous patients.

"Aqueous misdirection" or "malignant glaucoma" is characterized by flattening of the anterior chamber without pupillary block or choroidal effusion or suprachoroidal hemorrhage, usually with an accompanying rise in IOP. To explain the pathogenesis of this condition, Shaffer¹ proposed that aqueous is diverted posteriorly toward the vitreous cavity. Medical treatment,² laser surgery,^3,4 and vitreous surgery^5-9 have all been useful options to treat this condition.

We report a new method of surgical treatment for malignant glaucoma, consisting of vitrectomy and tube shunt implantation through the pars plana.

An 86-year-old white woman was first seen in our service in September 1996 because of a shallow anterior chamber associated with episodes of high IOP in the right eye. The patient had had 2 Nd:YAG laser peripheral iridotomies after cataract extraction, which had been performed 6 years before coming to us. The IOP was quite labile despite medicinal treatment. The left eye was amblyopic and had developed "pupillary block" after cataract extraction; a peripheral iridectomy had not helped control the IOP and the vision in the left eye had been lost.

On presentation, the visual acuity was 20/100 OD and no light perception in the left eye. The IOP was 42 mm Hg in the right eye and 12 mm Hg in the left. Treatment for the right eye was 2% dorzolamide hydrochloride thrice daily, 0.5% timolol maleate twice daily, 0.005% latanoprost at bedtime, and 50 mg of methazolamide orally twice daily, and treatment for the left eye was 1% prednisolone acetate twice daily and 1% atropine sulfate twice daily. The right eye had a shallow anterior chamber, 0.9 mm in depth (Figure 1). There were 2 patent peripheral iridotomies. The left eye had a deep anterior chamber. The anterior chamber angle was closed by peripheral anterior synechiae, 360° in both eyes. The optic disc of the right eye showed advanced glaucomatous cupping; the cupping was total in the left eye. Visual field examination of the right eye with a computerized perimeter (threshold strategy) revealed a severe constriction of the visual field, and with a marked depression of the retinal sensitivity in the arcuate areas. Ultrasound biomicroscopy ruled out ciliary or choroidal effusion or suprachoroidal hemorrhage.

Additional medical treatment was prescribed: 1% tropicamide 4 times daily, 1% atropine sulfate 4 times daily, and 2.5% phenylephrine hydrochloride 4 times daily. Topical and systemic aqueous suppressants were continued, but 24 hours later the anterior chamber depth and IOP were unchanged in the right eye. Neodymium:YAG laser capsulotomy was considered, but believed unlikely to be of adequate immediate benefit. The severity of the glaucomatous damage and high IOP, which prompted an urgent and effective intervention, and the presence of peripheral anterior synechiae in the anterior chamber angle, which would probably impede a satisfactory long-term control of IOP, were the factors considered in the surgical planning. The patient underwent a standard 3-port pars plana vitrectomy, removing the anterior vitreous and adhesions around the peripheral iridectomies; a Baerveldt (350 mm²) tube shunt was implanted through the pars plana. This surgical technique has been described elsewhere.^5-9 During the procedure, the anterior chamber deepened. The postoperative outcome was uncomplicated (Figure 2). Six months later, the visual acuity in the right eye was 20/80, IOP was 13 mm Hg with no medical treatment, the anterior chamber was deep, and there was no apparent complication.

A 72-year-old white woman developed pain and blurred vision in the left eye. She had previously had Nd:YAG laser peripheral iridotomies in both eyes and 2 weeks before coming to us had undergone an uncomplicated phacoemulsification with posterior chamber intraocular lens implantation in the left eye. The visual acuity was 20/30 OD and counting fingers at 120 cm OS. The IOP was 15 mm Hg in the right eye and 48 mm Hg in the left. Treatment in the left eye consisted of 0.5% timolol maleate twice daily, 0.2% brimonidine tartrate thrice daily, 2% dorzolamide thrice daily, and 1% cyclopentolate hydrochloride twice daily. The right eye had a clear cornea, a moderately shallow anterior chamber, 2 patent iridotomies, and a moderately dense nuclear cataract. The cornea of the left eye had diffuse corneal edema and a very shallow central anterior chamber but without lens-corneal touch. Two patent iridotomies were present at the 12- and 2-o'clock positions. Gonioscopy with indentation revealed a closed anterior chamber angle. The retina was attached, without peripheral choroidal or retinal abnormalities. The optic disc had moderate glaucomatous damage. Visual field examination was not performed.

The patient was treated with intravenous mannitol solution and oral acetazolamide; the current topical treatment was supplemented with 2.5% phenylephrine hydrochloride 4 times daily. The following day the corneal edema in the left eye persisted, the anterior chamber depth was unchanged, and the IOP was 29 mm Hg. Neodymium:YAG laser was not performed because of the lack of corneal clarity. The patient underwent a pars plana vitrectomy and a Baerveldt (250 mm²) tube shunt implantation. The tube tip was placed in the posterior segment through the pars plana. The anterior chamber deepened during the procedure. The postoperative period was uneventful. Four months after surgery in the left eye, the best-corrected visual acuity was 20/25, the anterior chamber was deep, and IOP was 10 mm Hg.

Malignant glaucoma or aqueous misdirection is initially managed with mydriatic-cycloplegic drops, aqueous suppressants, and hyperosmotics.² If medicinal therapy is unsuccessful, laser or surgical intervention is usually advised. Pars plana vitrectomy can be effective when other therapies fail, especially in pseudophakic and aphakic eyes.^5-9 However, after resolving the attack of aqueous misdirection itself, the IOP can remain elevated or even increase due to other factors. Chronic angle closure glaucoma and/or failure of previous filtering surgery can occur in cases of malignant glaucoma after successful pars plana vitrectomy: all 5 cases reported by Momoeda et al⁵ required medicinal treatment, and 2 of 5 patients required further filtration surgery after successful reversal of malignant glaucoma by pars plana vitrectomy, associated with intracapsular cataract extraction. The filtering bleb failed in 1 of the 2 patients with pseudophakic malignant glaucoma, which was treated by vitrectomy, as described by Lynch et al.⁶ Byrnes et al⁷ observed failure of the bleb after vitrectomy for ciliary block glaucoma in 4 of 19 cases. Harbour et al⁸ recently described 21 patients with malignant glaucoma treated with vitrectomy; 4 had postoperative visual loss due to progressive glaucoma.⁸

Although pars plana tube insertion with vitrectomy has been used to treat neovascular glaucomas and glaucomas associated with pseudophakia and aphakia,^10-12 to our knowledge, the use of this technique to treat malignant glaucomas has not been reported previously.

In the 2 patients described herein, prompt surgical intervention was indicated owing to the lack of response to the initial medicinal treatment, the level of IOP, the advanced glaucomatous damage (case 1), and the presence of corneal edema (case 2). In patients without advanced glaucomatous damage, medical treatment should be tried for 2 to 4 days before surgical intervention, and, when possible, Nd:YAG laser treatment can be tried. The satisfactory postoperative outcome probably reflects the efficacy of pars plana vitrectomy in treating the aqueous misdirection and tube shunt implantation in controlling the IOP. It is also likely that the tube inserted through the pars plana will prevent recurrence of this condition. However, it is not known whether more prolonged medical therapy or pars plana vitrectomy without tube shunt implantation would have been sufficient.

We suggest that pars plana tube insertion with vitrectomy can be a useful technique to treat patients with malignant glaucoma and a closed anterior chamber angle. This technique can effectively relieve the aqueous misdirection. The implantation of the tube shunt through pars plana can help prevent recurrence of this condition, and can help in long-term control of IOP in glaucomatous patients. This technique appears to be especially appropriate for patients with moderate or severe glaucomatous damage.

Dr Azuara-Blanco is now with Queen's Medical Centre, University of Nottingham, Nottingham, England.

Corresponding author: L. Jay Katz, MD, Wills Eye Hospital, 900 Walnut St, Philadelphia, PA 19107 (e-mail: ljk22222@aol.com).