MALIGNANT GLAUCOMA

Guest author

NAZMI USMANI

Ajmal Khan Tibbiya College

Aligarh

India

Introduction:

It is also known as:

Aqueous misdirection syndrome

Ciliary block glaucoma

Cilio-lenticular block

or Direct lens block glaucoma

The term “malignant glaucoma” was used by Von Graefe (1869) for a condition characterized by: “A shallow or flat anterior chamber with an inappropriately high intraocular pressure (IOP), despite a patent iridectomy”. 

As it was a violent form of secondary glaucoma (especially in the post-operative setting), that was resistant to treatment and often resulted in blindness (poor prognostic outlook), it was termed “malignant”.

It is regarded as a multifactorial condition that is thought to occur in anatomically predisposed eyes.

Etiology:

It may occur in phakic, pseudophakic or aphakic eyes.

It can occur following:

• Glaucoma filtering surgery (GFS) [especially in angle closure eyes].
• Other surgeries, such as: cataract surgery (with or without intra-ocular lens), scleral buckle, pars plana vitrectomy.
• Laser procedures: Nd:YAG cyclophotocoagulation, after laser-iridotomy or -sclerotomy 
• Implantation of a large optic intra-ocular lens (>7 mm).
• Use of miotics in predisposed eyes.

Idiopathic cases of malignant glaucoma (MG) have also been reported.

Prevalence:

2-4% angle closure glaucoma patients undergoing GFS develop malignant glaucoma.

2.3% post-keratoplasty patients and 1.3% patients who undergo GFS alone or combined with cataract extraction develop MG.

Females have 3 times higher risk of developing MG, as compared to men (apparently due to smaller ocular dimensions).

Predisposing factors:

• Axial hyperopia
• Nanophthalmos
• Chronic angle closure with plateau iris configuration 
• H/O malignant glaucoma in fellow eye
• A thick sclera may cause partial stenosis of vortex veins, impairing normal venous outflow and cause engorgement of choroid. Opening of anterior chamber during surgery lowers IOP suddenly with forward movement of the lens-iris diaphragm. This triggers MG in these eyes.
• A lens which is too large for the eye (disproportion between the volumes of the lens and eyeball predispose the eye to MG). The choroid gets edematous due to accumulation of blood when outflow is impaired. The ciliary body and iris rotate to the front closing access to the filtration angle from the back.
• In nanophthalmos the lens is larger in volume; there is decreased axial length and thickened choroido-scleral layer. This causes crowding of the anterior segment.
• A peripheral iridotomy does not prevent overfilling of the choroid (which leads to progressive angle closure).
• Eyes predisposed to develop MG have connective tissue related pathologies and accumulation of glycosaminoglycans in the vitreous.

  

Pathogenesis:

There are different theories which explain the development of malignant glaucoma=

I. Schaffer and Hoskins theory (“Posterior pooling of aqueous”): Aqueous flow is diverted posteriorly causing pooling (accumulation) of aqueous behind a posterior vitreous detachment. This shifts the lens-iris diaphragm anteriorly causing a pupillary block.

II. Chandler and Grant theory (“Slackness of lens zonules”): Laxity of lens zonules coupled with positive vitreous pressure causes a forward movement of lens. This sets up a vicious cycle in which the higher the pressure in the posterior segment, the more firmly is the lens pushed forward.

III. Quigley et al. (“Choroidal expansion”): The precipitating event is choroidal expansion which increases vitreous pressure. The initial compensatory outflow of aqueous along the postero-anterior pressure gradient causes shallowing of the anterior chamber.

IV. Final common pathway:

Establishment of vicious cycle whereby the transvitreal pressure cannot be established by outflow of aqueous humor -> Fluid buildup behind the vitreous leads to vitreous condensation which exerts a forward force -> Anterior displacement of the lens-iris diaphragm 

Classification:

Classical malignant glaucoma: It is a rare complication of incisional surgery for primary angle-closure glaucoma. It is independent of the type of surgery and preoperative IOP. It can occur immediately after surgery to many years later. In the early postoperative period it is related to cessation of cycloplegic drugs. There is partial or total closure of the drainage angle at the time of surgery and axial hypermetropia is associated with increased risk of MG.

Nonphakic malignant glaucoma: Develops in patients after cataract extraction. It may occur with or without antecedent glaucoma.

   

Malignant glaucoma in aphakia

Malignant glaucoma in pseudophakia

Miotic induced malignant glaucoma: Perhaps associated with contraction of ciliary body or associated with forward shift of the lens leading to shallowing of anterior chamber. 

Others: Malignant glaucoma associated with bleb needling, infection and inflammation and other ocular disorders.

Spontaneous malignant glaucoma: MG may develop spontaneously in the absence of previous surgery, miotic therapy or any other apparent cause. 

Evaluation:

Medical history=

1. Determination of predisposing factors

2. Symptoms: Patients usually present with red, painful eye, decreased vision (similarly to pupillary-block glaucoma). Headache, nausea and vomiting may also occur, depending on IOP. Myopic shift related to anterior movement of lens-iris diaphragm, with secondary improvement of near vision occurs. Persistent symptoms due to anterior synechiae associated with long-standing shallowing of anterior chamber.

Slit-lamp examination:

Anterior chamber depth= Central & peripheral shallowing of the anterior chamber.

Patency of iridotomy should be examined. If none is visible, an iridotomy should be attempted.

Iris is not bowed anteriorly (iris bombe’ of Angle Closure Glaucoma)

Vitreous may have optically clear spaces. This can also be seen on B-scan ultrasound.

Seidel test should be performed to exclude filtering bleb leaking after filtration surgery. Such cases present with hypotony.

Posterior segment should be examined or assessed by ultrasound to rule out choroidal detachment or suprachoroidal hemorrhage.

Tonometry and gonioscopy should be performed.

Ultrasound Biomicroscopy (UBM):

Anterior rotation of ciliary processes, which press against the lens equator (or the anterior hyaloid in aphakia) and prevents forward flow of aqueous (hence the term ciliary block glaucoma). 

In some cases UBM has shown the size of the lens to be smaller than normal, that may allow the lens to move forward within the eye.

Differential diagnosis:

1. Acute angle closure glaucoma: Anterior chamber depth is not uniform (centre deeper). Responds to peripheral iridotomy. 
   
2. Choroidal detachment/effusion: Usually inflammatory in nature (trauma, following surgery, scleritis, chronic uveitis, Vogt-Koyanagi-Harada disease, following cyclo-photocoagulation/cryotherapy). IOP is normal or reduced. 
3. Suprachoroidal hemorrhage: Shallowing of anterior chamber, increased IOP, sudden pain, hemorrhagic/non-serous detachment of the choroid. Usually occurs within one week of surgery.

Management:

Shallow AC beyond 5 days may cause formation of peripheral anterior synechiae, posterior synechiae, cataract and damage to corneal endothelium.

• Medical
• Laser
• Surgery
• Management of fellow eye

Hyperosmotic agents= 20% mannitol IV reduces the pressure exerted by vitreous (oral glycerol can also be substituted if mannitol is not available or contraindicated).

Mydriatic-cycloplegic= Combination therapy with 1% Atropine and 10% phenylephrine drops causes relaxation of ciliary muscle and tighten the zonules, pulling the anteriorly displaced lens backwards.

Aqueous suppressants= Beta-blockers or alpha2-agonists or carbonic anhydrase inhibitors are utilized to reduce the IOP.

Anti-inflammatory agents= Topical steroids are used to control the inflammation. 

Maintenance therapy= The patient is put on life-long atropine drops to prevent recurrence. Atropine can be instilled once every 4-6 weeks and every time patient notices any refractive change due to AC shallowing the treatment can be re-instituted. 

Miotics are contraindicated for life.

In case there is no response within 5 days, laser and/or surgery is employed.

Laser treatment= Nd-YAG laser hyaloidectomy, to disrupt the anterior vitreous face and establish proper flow of aqueous, can be undertaken in aphakic and pseudophakic eyes. (3-11 mJ energy). 

Argon laser for photocoagulation of the ciliary processes to destroy the ciliary processes and reduce aqueous production can be attempted. If not possible through an iridotomy, trans-scleral cyclphotocoagualtion can be done.

Surgery= When Medical or laser therapy fails surgical intervention is required. It involves vitrectomy to reduce the vitreous volume and promote aqueous flow into the anterior chamber. Usually a combination of posterior scelerectomy and air injection in the anterior chamber, anterior pars plana vitrectomy and lens extraction is done.

Prophylactic measures:

Cessation of miotic drops should be done as soon as possible.

Conclusion:

Malignant glaucoma is a therapeutic challenge.

Patients with H/O malignant glaucoma in fellow eye and PACG should be closely followed after glaucoma surgeries.

Patients have relatively good prognosis with current therapeutic modalities. More than 50% patients apparently respond to conservative management.