Malignant glaucoma


Malignant glaucoma

Description, Causes and Risk Factors:

Secondary glaucoma caused by forward displacement of the iris and lens, obliterating the anterior chamber; usually follows a filtering operation for primary glaucoma.

The term malignant glaucoma was used for the first time by von Graefe to describe a rare, severe form of glaucoma following an eye surgery, which was unresponsive to common therapies and had a bad prognosis. Malignant glaucoma is an event that occurs as a complication of anti-glaucoma surgery with a marked increase in IOP accompanied by abolition or extreme reduction of the anterior chamber. The malignant glaucoma embrace many different forms, characterized by common criteria, high IOP originating from the vitreal cavity, forward shift of the iris-lens diaphragm with reduction or abolition of the anterior chamber, deleterious effect of cholinergic drugs and favorable effect of cycloplegic agents, monolateral initial onset with development of bilateral glaucoma if similar circumstances occur.

Malignant glaucoma is an entity characterized by elevated intraocular pressure (IOP) with a shallow or flat anterior chamber in an eye with a patent peripheral iridotomy/iridectomy. This condition is reported to develop in 2-4% of patients with a history of acute or chronic angle closure glaucoma who have drainage surgery, although recently it is believed to be much less frequent. Malignant glaucoma has been described following cataract surgery with and without intraocular lens (IOL) implant, implantation of large IOLs, starting miotic treatment, stopping cycloplegic treatment, laser iridotomy, laser capsulotomy, glaucoma drainage device implantation, trabeculectomy, and intravitreal triamcinolone injection. Many terms have been used to describe this syndrome including aqueous misdirection, ciliovitreal block, ciliary block, and cilio-lenticular block.

The Pathophysiology of malignant glaucoma is not well understood. The underlying pathology of malignant glaucoma is believed to be aqueous misdirection into or posterior to the vitreous body with anterior displacement of the lens-iris diaphragm.

Although the cause of the aqueous misdirection has not yet been elucidated, many clinicians believe the anterior rotation of the ciliary body with ciliary processes pressed against the lens along with anterior displacement of the vitreous is responsible for the aqueous misdirection. The anterior displacement of the vitreous put it in apposition to the ciliary processes contributing to the misdirection.

Malignant glaucoma occurs significantly more frequently after penetrating surgery than in the case of non-penetrating surgery, after just the glaucoma surgery than after treatment combined with phacoemulsification, as well as in eyes with narrow angle glaucoma. It was most commonly observed after laser iridotomy, phacoemulsification of cataract, posterior capsulotomy using a laser/Nd:YAG laser (neodymium:yttrium aluminum garnet laser) cyclophotocoagulation, after implantation of large-sized IOLs, after local application of miotics, after suturolysis.

Symptoms:

Patients with malignant glaucoma will present with anterior chamber that is shallow both peripherally andcentrally, or axially shallow. Intraocular pressure will beelevated. Thepatient may complain of a red, painful eye and blurredvision. The patient may also experience nausea andvomiting as with an acute primary angle closure attack.

Diagnosis:

Epstein proposed minimum requirements for a diagnosisof malignant glaucoma including: an axially shallowanterior chamber; elevated IOP; presenceof a patent PI (peripheral iridotomy/iridectomy); and absence of suprachoroidal fluid. A careful ocular surgical history is alsoimportant to diagnosing malignant glaucoma as it mostcommonly follows glaucoma filtration surgery, cataractsurgery, combined filtration and cataract surgery, andsurgical peripheral iridotomy/iridectomy.More recently, UBM (ultrasound biomicroscopy) has proven useful in distinguishingmalignant glaucoma from other similar conditions and indetermining the efficacy of various treatments.

Other useful findingsin diagnosis of malignant glaucoma, slit lamp biomicroscopy willreveal an axially shallow or flat anterior chamber, gonioscopy will demonstrate a closed angle; tonometry willshow elevated IOP; and funduscopicexamination or B-scan ultrasonography will show noelevation of the retina and choroid.

Treatment:

The first line of treatment for malignant glaucoma is Medical therapy. Approximately 50% of patients with malignant glaucoma can be treated by medical therapy alone. Medical management consists of cycloplegic drops, aqueous suppressants, and hyperosmotic agents. Some authors also advocated mydriatic drops such as phenylephrine initially. This combination dehydrates the vitreous, decreases ongoing aqueous production, and promotes posterior movement of the lens-iris diaphragm. Atropine is the most commonly used agent for cycloplegia. Aqueous suppressants include topical beta-blockers, oral or topical carbonic anhydrase inhibitors (Diamox™ and Trusopt®™), and alpha agonists (brimonidine). To reduce vitreous volume, hyperosmotic agents can be given systemically (glycerol, mannitol). Medical treatment may take up to 5 days to be successful. Once the anterior chamber depth and IOP normalize, the medications can be gradually discontinued. Initially, the hyperosmotic agents should be discontinued; following this the aqueous suppressants can be withheld. Atropine may need to be continued long-term or even indefinitely. Not infrequently, the ciliary block will return after discontinuation of atropine.

Many patients do not adequately respond to medical therapy and require more invasive intervention. If after starting medical therapy there continues to be iridocorneal touch or the IOP is still high, surgical intervention is needed. Delay in surgery predisposes the eye to peripheral anterior synechiae, posterior synechiae, corneal endothelial decompensation, cataract formation, and optic nerve damage. Vitrectomy has become the preferred surgical treatment for malignant glaucoma since the advent of microsurgical techniques. Momoeda first described anterior vitrectomy with intracapsular cataract extraction as a treatment in 1983. This was shortly followed by pars plana vitrectomy being described by Lynch in 1986.

The Argon laser has been used through a patent peripheral iridectomy in the attempt to shrink ciliary processes and then presumably break the block. Argon laser settings are typically 100 to 300 mWs, 0.1-0.2 seconds duration, and a spot size from 50 to 100 microns.

In patients who are aphakic or pseudophakic, Epstein proposed the use of Nd:YAG laser to create flow from the vitreous around the IOL into the anterior chamber. Since this initial report, many others have shown success with this method as well. The Nd:YAG laser is used to create a posterior capsulotomy and an anterior hyaloidotomy. This method is technically difficult and not effective in eyes with large IOL's or capsular synechiae to the IOL. In IOL's with a dialing hole, making the capsulotomy through the hole may improve the flow from the vitreous to the anterior chamber.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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