BASICS

DESCRIPTION

• An uncommon form of secondary glaucoma occurring post intraocular surgery characterized by a flat or shallow anterior chamber, absence of pupillary block, and elevated intraocular pressure. Expansion in vitreous volume due to sequestration of aqueous in the posterior segment with resultant anterior shift in the lens iris diaphragm.

• “Malignant glaucoma” – named by Von Graefe in 1869 – refers to the likelihood that this progressive condition will not improve spontaneously.

– Synonyms: Aqueous misdirection syndrome, ciliary block glaucoma, and ciliovitreal block.

EPIDEMIOLOGY

Incidence

• 2–4% in eyes undergoing glaucoma filtration surgery for angle closure glaucoma (1)

• Can occur at any time following surgery

• No established racial, sexual predilection

RISK FACTORS

• Small eyes with small anterior hyaloid surface

• Filtering surgery in eye with history of angle closure such as shallow chamber and peripheral anterior synechia

• History of malignant glaucoma in fellow eye

Genetics

Unknown for malignant glaucoma – but smaller eyes with angle closure have predisposition to development of malignant glaucoma, and eye size has a genetic basis with many genes associated with angle closure (2).

GENERAL PREVENTION

Involves preoperative identification of high risk eyes – small eyes with a history of angle closure or that of malignant glaucoma.

PATHOPHYSIOLOGY

• Under homeostatic conditions, aqueous volume flows predominantly anteriorly exiting through trabecular and uveoscleral outflow pathways and, to a lesser degree, aqueous circulates posteriorly into and around the vitreous body.

• Under pathologic conditions, a shift to greater aqueous flow posteriorly occurs incited by sudden anterior chamber decompression (i.e., anterior chamber entry, overfiltration). When combined with a fundamentally decreased rate of aqueous exchange from the ciliary processes both across the anterior hyaloid and through the vitreous gel, the result is vitreous volume expansion through aqueous sequestration, and an anterior shift of the lens–iris diaphragm axis. The anterior chamber space is consequentially shallowed or flattened, further obstructing aqueous outflow through angle closure resulting in elevated IOP.

ETIOLOGY

• The exact initiating event is not known but appears strongly related to an abnormal interaction between the ciliary processes, the lens, and the anterior vitreous face, seemingly induced by postoperative anterior chamber decompression leading to an anterior shift in the lens–iris diaphragm and diversion of aqueous into the vitreous cavity (3).

• Smaller/hyperopic eyes – with tendency toward angle closure glaucoma, have correspondingly smaller anterior hyaloid surface area, and less space between the ciliary processes and the anterior hyaloid. Consequentially, if a shift in the lens–iris diaphragm occurs abruptly, contact between the ciliary processes and anterior hyaloid occurs. Aqueous is then disproportionately circulated posteriorly with resultant vitreous volume expansion and further flattening of the anterior chamber with elevation in intraocular pressure.

COMMONLY ASSOCIATED CONDITIONS

• Chronic angle closure

• Hyperopia

• Nanophthalmos

DIAGNOSIS

HISTORY

Malignant glaucoma can present any time after any intraocular surgery in phakic, pseudophakic, or aphakic eyes, but most typically arises in eyes with a history of angle closure undergoing glaucoma filtration surgery. It has been reported rarely after laser iridotomy and miotic administration.

PHYSICAL EXAM

• Shallow anterior chamber: Uniform decrease in anterior chamber depth centrally and peripherally.

• Absence of pupillary block: Reflected by presence of patent iridotomy/iridectomy.

• Elevated intraocular pressure (IOP)

– IOP may not be present, or only modestly elevated in the early stages of ciliary block in the presence of a filtering procedure.

• Absence of simulating conditions causing posterior volume expansion: Choroidal effusion, hemorrhage: As visualized with indirect ophthalmoscopy.

DIAGNOSTIC TESTS & INTERPRETATION

Lab

• Slit-lamp exam may reveal elevated bleb initially with gradual flattening and disappearance upon further posterior misdirection and sequestration of aqueous.

• Gonioscopy may reveal closed angle or obscured angle structures, and possibly visualization through the iridotomy of ciliary processes pushed forward.

Imaging

• Ultrasound biomicroscopy (UBM) can demonstrate irido-corneal contact, decreased anterior chamber depth, forward displacement of the lens–iris diaphragm, and ciliary processes.

• B-mode ultrasound can confirm absence of posterior space-occupying mechanism such as choroidal hemorrhage or effusion if visualization is poor with indirect ophthalmoscopy.

Diagnostic Procedures/Other

• Anterior-segment optical coherence tomography (AS-OCT): Can noninvasively demonstrate anterior chamber angle structures and quantitatively assess the anterior chamber angle

• Laser iridotomy: Must be performed if not already present to diagnostically exclude pupillary block, and therapeutically relieve block if present

• Fluorescein injection through peripheral vein, with visualization of fluorescein-tinged aqueous fluid flowing posteriorly shortly thereafter can confirm diagnosis

Pathological Findings

• Smaller eyes have thicker sclera with a reduced ability to remove suprachoroidal fluid.

• Malignant glaucoma has been proposed to involve a pathologic behavior of the vitreous gel with poor vitreous conductivity of fluid (4).

DIFFERENTIAL DIAGNOSIS

• Pupillary block

– Will typically demonstrate elevated IOP, preserved central anterior chamber depth, closed angle, and iris bombé of variable degrees. If patency of iridotomy is doubted, then another should be performed to exclude pupillary block.

• Choroidal effusion

– Serous: Gray–light brown choroidal elevation directly visualized or observed with B-scan ultrasound. Typically associated with low IOP, and shallow anterior chamber. Must consider overfiltration or wound leak if following filtration surgery.

– Hemorrhagic: Dark-brown or red effusion directly visualized or observed with B-scan ultrasound. Typically associated with uniform anterior chamber shallowing or flattening, increased IOP, and frequently preceded by pain.

• Overfiltration

• Shallow anterior chamber associated with low IOP. If low IOP is accompanied by high/diffuse bleb morphology: Likely overfiltration. If low IOP is accompanied by low/flat bleb: Must exclude bleb leak.

• Lens related angle closure: With anterior shift of lens–iris diaphragm and resultant angle closure.

– Phacomorphic glaucoma: Anterior shift due to intumescent lens

– Lens dislocation: Anterior shift due to zonular laxity as in pseudoexfoliation or other predisposing condition (i.e., Marfan’s, trauma, etc.)

• Infusion misdirection syndrome

– Intraoperative condition due to misdirection of irrigating fluid posteriorly, potentially through iridotomy or zonular dehiscence – expanding vitreous volume and resultant anterior shift of iris/posterior capsule.

TREATMENT

MEDICATION

• Cycloplegia/mydriasis: Widens ciliary body diameter through contraction of dilator muscle of iris increasing diffusional area for aqueous; pulls lens posteriorly by tightening zonules through unopposed action of longitudinal muscle with circular muscle paralysis.

• IOP management

– Aqueous suppression: Beta-blockers, carbonic anhydrase inhibitors, and alpha-agonist

– Osmotic agents (Mannitol, Isosorbide): Decrease vitreous volume by increasing osmotic gradient between blood and ocular fluids causing fluid to be drawn intravascular

Geriatric Considerations

Osmotics are relatively contraindicated in patients with renal or cardiovascular compromise. Signs of atropine toxicity should be monitored in elderly patients.

Pediatric Considerations

Alpha agonists have potentially serious adverse effects in children and are contraindicated in children <2 years old.

Pregnancy Considerations

Aqueous suppressants and osmotic agents are classified as class C in pregnancy – with fetal risk revealed in animal studies, but not established or studied in humans.

ADDITIONAL TREATMENT

General Measures

• Miotics contraindicated

• If attack broken medically (chamber deepening, normalization of IOP), can taper off hyperosmotics, and aqueous suppressants with long-term use of cycloplegia/mydriasis due to risks of reoccurrence

Issues for Referral

• Patients not adequately responding to medical therapy require surgical intervention.

• Response may develop days after initiating medical therapy.

SURGERY/OTHER PROCEDURES

• Nd: YAG laser disruption of anterior hyaloid face: Can be attempted in typically aphakic or pseudophakic patients not responding to medical therapy (5)[C]. Response can be observed as progressive deepening of anterior chamber over hours–days. If view is precluded by posterior capsule opacification, capsulotomy should be undertaken prior to vitreous face disruption.

• Surgical vitrectomy with opening/disruption of anterior hyaloid face, removal of sufficient vitreous to disrupt pockets of aqueous, with ultimate goal to create unicameral eye – with a direct communication between the anterior and posterior chamber (6)[C].

IN-PATIENT CONSIDERATIONS

Initial Stabilization

Medical consultation and consideration for admission is necessary if medical comorbidities such as cardiac, respiratory, renal conditions are present.

Admission Criteria

Hospital admission may be required for monitoring during parenteral osmotic administration, and/or pain control, or urgent surgical intervention if warranted.

IV Fluids

• Osmotics agents

• Intravenous carbonic anhydrase inhibitor can be administered for aqueous suppression.

Nursing

Adherence to parenteral medication administration guidelines, and topical medication schedule administration with appropriate monitoring during therapy.

Discharge Criteria

Controlled pain, stabilization/improvement in condition.

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Degree and duration of flat anterior chamber, level of IOP, and degree of patient comfort are all carefully monitored with urgency and frequency of follow-up based on response to intervention and progress.

Patient Monitoring

• Long term surveillance for reoccurrence is required with careful monitoring upon cessation of cycloplegia.

• If any intraocular surgery is required in fellow eye, precautionary measures taken to avoid sudden anterior chamber decompression or overfiltration, and consideration should be given for pre/postoperative cycloplegia/mydriasis.

PATIENT EDUCATION

• Risks of malignant glaucoma with surgery in fellow eye, and risks of reoccurrence in operated eye should be discussed with patient.

• Adherence to prescribed medical therapy, particularly long term cycloplegia should be emphasized.

PROGNOSIS

• Approximately 50% of cases will respond medically within 5 days.

• Surgical success rates are higher in pseudophakic eyes as compared to phakic eyes (6)[C].

COMPLICATIONS

• Reoccurrence/persistence

• Corneal decompensation

• Cataract progression

• Glaucomatous progression

• Vitreous traction with retinal tear/detachment

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