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September 24,2006 Dr Sanjay Shrivastava 1

Angle Closure GlaucomaCurrent Concepts

Dr Sanjay ShrivastavaProfessor of Ophthalmology

Regional Institute of OphthalmologyGandhi Medical College, Bhopal


Definition

• Angle Closure Glaucomas are characterized by apposition of peripheral iris against trabecular meshwork, resulting in obstruction of aqueous outflow.


• Primary Angle Closure Glaucoma term is used when mechanism of angle closure glaucoma is not felt to be associated with other ocular or systemic abnormalities or because the mechanisms are not well understood. In this condition pupillary block glaucoma, plateau iris and combined mechanism glaucoma have been included.


• Secondary Angle Closure Glaucoma is associated with ocular or systemic abnormalities or due to apparent mechanism such as membrane contraction or space occupying lesions pushing iris forward to close angle.


Epidemiology

• Glaucoma is second leading cause of blindness world wide. It has been estimated that by 2010 there will be 60.5 million glaucoma affected people with approximately 26% with angle closure glaucoma.

• Angle closure glaucoma is less common than chronic open angle glaucoma.

• Angle closure glaucoma is common among Asians and Eskimos but uncommon among Africans and Caucasians


Epidemiology

• The precise ratio between the two has not been established. Reported figures from some of the western countries indicates incidence of angle closure glaucoma as 0.5% in general population and 2-3 % in >40 years age group.

• Prevalence of 1.58% has been reported in rural south Indian population by Lingam & co-workers (2006)


Epidemiology

• West Bengal study has reported glaucoma in 2.63% cases in 1594 individuals >50 years examined.

• Another study has estimated that ½ of 67 million people diagnosed with glaucoma has primary angle closure glaucoma. According to this study 6.7 million people globally are irreversibly blind due glaucoma.


Stages of Glaucoma

1. Initiating events

2. Structural alterations

3. Functional alterations

4. Optic nerve damage

5. Visual loss


Stages of Glaucoma

Stages representing:

* The series of events, leading to

* Tissue changes, leading to

* Physiologic changes, leading to

* Axonal loss, leading to

* Visual field loss (progressive)


Stages of Glaucoma

* Stage I – Initiating events may be genetic or acquired

* Stage II- Tissue changes are associated with aqueous outflow system with vascular and structural alteration in optic nerve head.

* Stage III- Physiologic changes are associated with elevated IOT, reduced vascular perfusion, laminar deformity


Stages of Glaucoma

* Stage IV – Axonal Loss leads to

*Stage V - Glaucomatous optic neuropathy that is associated with Glaucomatous field loss


Classification of the Glaucomas Based on Initial events

A. Open Angle GlaucomasB. Angle Closure Glaucomas

1. Pupillary Block Glaucoma2. Plateau Iris Syndrome3. Combined mechanism Glaucomas

C. Developmental GlaucomasD. Glaucomas Associated with other ocular and systemic disorders


Pupillary Block Glaucoma

• Also called primary angle closure Glaucomas – Acute– Sub-acute– Chronic angle closure

• Creeping angle closure• Combined mechanism glaucoma


Classification of the Glaucomas based on mechanism of outflow obstruction

I. Open Angle Glaucoma mechanism

II. Angle Closure Glaucoma Mechanism

III. Developmental Anomalies of the Anterior Chamber Angle


Angle Closure Glaucoma Mechanism

A. Anterior (Pulling Mechanism)

1. Contracture of Membranes (Neovascular Glaucoma, ICE Syndrome, Post polymorphous dystrophy, Ocular Trauma)

2. Contracture of Inflammatory precipitates


Angle Closure Glaucoma Mechanism… Contd.

B. Posterior (Pushing Mechanism)

1. With Pupillary block : Pupillary Block Glaucoma- Lens Induced Mechanism (Intumescent lens, subluxation of lens, mobile lens syndrome), Post synechiae (Iris-vitreous block, pseudophakia, Uvietis)


Angle Closure Glaucoma Mechanism… Contd.

2. Without Pupillary block- Plateau iris syndrome, malignant glaucoma, forward vitreous shift, scleral buckling, following PRP, CRVO, Intra ocular tumours , cysts of iris & ciliary body, ROP, PHPV


Pupillary Block Glaucoma

Is characterized by functional block between pupillary border of iris and ant lens surface, usually associated with mid dilated pupil. This leads to build up of aqueous pressure in posterior chamber leading to forward shift of the peripheral iris and a closed anterior chamber.


Theories of mechanism of angle closure glaucoma

• Relative Pupillary Block: Increased resistance to aqueous flow from posterior to anterior chamber between iris and lens , the musculature of iris exert a backward pressure against the lens that increases the resistance to flow of aqueous into AC resulting in increase in pressure in PC causes forward bulge in peripheral iris.


Stages of Angle Closure

1. Iridocorneal contact

2. Iridotrabecular contact


Anatomical Risk Factors for Pupillary Block

• Shallow AC, Thick anteriorly placed lens , smaller diameter of cornea, shorter posterior curvature of cornea, shorter axial length , relative anterior insertion of iris, narrow angle of AC and loose zonular ligaments.


Pupillary Dilatation

• Mid dilated pupil of 3.5 to 6 mm is critical limit of dilatation to cause acute attack

• Pupillary block force of dilator and sphincter muscle and stretching force of iris are greatest on iris in mid dilated position (of 3.5 to 4.5 mm size)


Mechanism of Chronic Angle Closure Glaucoma

• Peripheral Anterior Synechiae (PAS) may develop with prolonged or recurrent acute or subacute attack leading to chronic angle closure glaucoma

• PAS in acute angle closure are broad based and are seen in superior quadrant and correlate with duration of acute attack


Mechanism of Chronic Angle Closure Glaucoma

• Synechial closure is referred to as shortening of the angle – creeping angle closure. This condition can be prevented by timely peripheral iridotomy.


Irido- corneal Contact

Ten major factors may combine to produce irido-corneal contact:

Static factors

1. Curvature of Cornea

2. Curvature of Anterior lens surface

3. Modulus of elasticity of iris stroma


Irido- corneal Contact… Contd

Factors that can develop an acute change

4. The sphincter muscle force

5. The dilator muscle force

6. The force that results from iris stromal strech E

7. Anterior Chamber depth


Irido- corneal Contact… Contd

Subsidiary factors

8. Aqueous inflow

9. Facility of out flow

10 Pigment release


Occludable Angle

• Occludable angle is the eye in which the pigmented trabecular meshwork is not visible without indentation in atleast 3 out of 4 quadrants. The drainage angle in such eyes is generally grade II or less i.e. less than 20 degrees. No other gonioscopic abnormality is present


Occludable Angle

• Some reports have concluded that considering definition of occludable angle for epidemiological studies will lead to misclassification of many subject with PACG as POAG as the current definition of occludable angle is too stringent. According to these authors history, clinical examination and static and dynamic gonioscopy remains the diagnostic gold standard. (Foster P.J. et al 2003).


Types of Angle Closure Glaucoma

(Based on symptoms and Clinical Findings)

1. Acute angle closure glaucoma

2. Sub-acute angle closure glaucoma (also called intermittent/ prodromal or sub-clinical glaucoma). Sub-acute glaucoma may lead to acute angle closure glaucoma or chronic angle closure glaucoma


Types of Angle Closure Glaucoma

3.Chronic Angle Closure Glaucoma

4. Combined Mechanism Glaucoma


Plateau Iris

Plateau Iris Configuration and Plateau Iris Syndrome

• The definitions of these entities are included here because they are primary conditions that are often difficult to distinguish from the PAC entities resulting from pupillary block.


Plateau Iris

Plateau iris configuration is characterized by a near-normal-depth central anterior chamber, a flat iris profile, and crowding of the anterior-chamber angle by the iris base. The IOP may be normal or elevated. The condition appears to be related to a forward displacement of the ciliary processes that causes anterior displacement of the peripheral iris and angle closure. Such closure occurs without a significant pupillary block component.


Plateau Iris

• Plateau iris syndrome is defined as having a plateau iris configuration with a closed anterior-chamber angle and usually with elevated IOP, which persists despite the elimination of anypupillary block component by a patent iridotomy. Intraocular pressure elevation that was presentbefore iridotomy may persist; the IOP typically increases after pupil dilation, which causes greater occlusion of the angle by the peripheral iris.


Combined Mechanism Glaucomas

• Combined mechanism glaucomas refers to condition in which both, open angle and angle closure components are present

• After successful treatment of angle closure glaucoma with iridotomy , eliminating all appositional closure the IOP still remains elevated. PAS may or may not be present


Combined Mechanism Glaucomas

• An eye with open angle glaucoma may develop angle closure due to natural development of pupillary block or result from miotic therapy


Mechanism of Combined Glaucoma

I. Open angle glaucoma complicated by angle closure

• Co-incidental occurrence

• Miotic induced

• Swelling of lens

• Flat AC after intraocular surgery

• PAS after ALT, PAS following inflammation



II Primary angle closure with trabecular damage (due to acute, sub-acute or chronic angle closure)

III Secondary open angle glaucoma with superimposed secondary angle closure glaucoma (post traumatic , idiopathic, uveitic glaucoma is complicated by PAS due to recurrence of inflammation)



IV Primary open angle glaucoma with superimposed secondary open angle glaucoma (Secondary to trauma or inflammation)

V. Elevated episcleral venous pressure casing impaired outflow facility (Thyroid Ophthalmopathy, Carotico cavernous fistula, Struge Weber Syndrome)


Diagnostic Situations

• During the course of ocular examination, on the basis of suspicious findings

• Patient may present with symptoms and signs suggestive of angle closure glaucoma.


Risk Factors

I. General Features of Patients

a. Age: Bimodal peak, at ages 53 – 58 years and at 63-70 years

b. Race: Less common amongst black

c. Sex: significant predominance of females

d. Refractive Error: More common in hypermetropes


Risk Factors

e. Family History: generally believed to be inherited

f. Systemic disorders: type II Diabetes is associated with decreased anterior chamber depth


Precipitating Factors

I Factors that produce mydriasis

a. Dim illumination

b. Emotional stress

c. Drugs (Mydriatics – anticholinergics including Botulinum toxin and adrenergics


Precipitating Factors

II Factors that produce miosis, strong cholinesterase inhibitor miotics like di-isopropyl fluorophosphate and ecothiophate iodide

III Sulpha based compound that produce transient myopia due to lens swelling and forward movement of lens iris diaphragm


Clinical Features

OCULAR FINDINGS

a. Intraocular tension (IOT) – tonometry, tonography

b. Evaluation of peripheral anterior chamber

* Penlight examination

* Slit lamp examination for peripheral anterior chamber depth


Clinical Features .. contd

Slit Lamp examination (ven Herick’s method)

Grade IV or larger – PAC > or equal to 1CT

Grade III – PAC = ¼ - ½ CT

Grade II – PAC = ¼ CT

Grade I – PAC < ¼ CT


Clinical Features … contd

Slit Lamp examination (van Herick’s method)

Peripheral anterior chamber depth of < ¼ is considered dangerously narrow anterior chamber angle

* Gonioscopy is indicated particularly when peripheral AC depth is shallow, Static and dynamic (indentation)


The Grading System for Van Herick’s Technique

Classification - Gonioscopic Appearance

Wide open - All structures visible

Grade I narrow - Difficult to see over iris root into recess

Grade II narrow - Ciliary body band obscured

Grade III narrow - Posterior trabeculum obscured

Grade IV narrow (closed) - Only Schwalbe’s line visible


Gonioscopic Interpretation

• Sheie proposed system based on extent of visualization of anterior chamber angle structures.

• Shaffer suggested grading on the basis of angular width of angle recess

• Spaeth suggested evaluation of angular width of angle recess, configuration of peripheral iris and apparent insertion of iris root.


Newer Techniques

• Ultrasound Biomicroscopy

• Radioimaging

• OCT

• Optic nerve head (ONH) and retinal nerve fiber layer (RNFL) assessments


ONH and layer RNFL assessments

Qualitative

o Slit lamp biomicroscopy examination using non-contact lenses (eg, 90-D lens) or contact lenses (eg, central lens in Goldmann 3-mirror lens). Green filter may aid in the identification of RNFL thinning.

o Fundus photography for documentation (stereoscopic or nonstereoscopic)


ONH and layer RNFL assessments

Quantitative

o GDx VCC nerve fiber analyzer

o Heidelberg retinal tomography (HRT)

o Optical coherence tomography (OCT)


Shaffer’s Gonioscopic Classification of the Anterior Chamber Angle

• Grade Angular Width Clinical Interpretation• A Wide open (20° to 45° Closure

improbable• B Moderately narrow

(10° to 20°) Closure possible• C Extremely narrow Closure possible• D Partially/totally closed

Closure present


Spaeth’s Gonioscopic Classification of the Anterior Chamber Angle

Site of iris insertion Anterior to trabecular meshwork, Schwalbe's

line Behind Schwalbe's line, trabecular

meshworkScleral spur Deep angle recess, anterior ciliary body

band Extremely deep, posterior ciliary body band


Peripheral iris configuration

• b = bowed

• f = flat

• p = plateau

• c = concave

• Degree of iris bowing (IB): 0 to 4+


Provocative tests

1. Mydraitic Provocative test: topical Tropicamide 1% rise of IOT of 8 mm of Hg or more is considered positive test.

2. Dark Room Provocative test: Exposure to dark for 60 – 90 min – rise of 8 mm of Hg or more is considered positive test.

3. Prone Provocative test : Prone position for 60 min , rise of 8 mm of Hg or more is considered positive test


Provocative tests … contd

4. Pilocarpine/Phenylephrine Provocative Test: 2% Pilocarpine and 10% Phenylephrine are instilled simultaneously every minute for 3 applications to achieve mid dilated pupil – rise of 8 mm of Hg or more is considered positive test.If negative repeat the test . If negative after 90 min, test is terminated by 0.5% Thymoxamine (alpha adrenergic agonist)


Value of Provocative Tests

Questionable

Accurate history and meticulous physical examination provides the best guide.


Symptoms of Angle Closure Glaucoma

• Sub-acute angle closure Glaucoma – dull ache, slight blurring

• Acute angle closure Glaucoma – Pain, redness, blurred vision

• Chronic angle closure glaucoma – Asymptomatic or visual field defects


Signs

1. External Ocular Examination

2. Slit lamp examination

3. Gonioscopy including compressive gonioscopy to differentiate appositional angle closure from synechial closure

4. Fundus examination (Hyperaemic and edematous disc. CRVO may occur during acute angle closure glaucoma


Signs

5. Visual fields shows non-specific constriction. It may be constriction of upper field or nerve fibre bundle defect.


Differential Diagnosis of acute angle closure Glaucoma

1. Neovascular Glaucoma

2. Inflammatory causes (Post synechiae , iris bombe)

3. Iridocorneal endothelial Syndrome (ICE)

4. Ciliary body engorgement or suprachoroidal effusion caused by systemic drugs like Topiramate, Sulphonamide and Phenothiazine



5. Ciliary body engorgement associated with retinal vein occlusion or PRP

6. Ciliary body block syndrome

7. After incisional or LASER PI

8. Phacomorphic lens induced glaucoma



9. Developmental anomalies like nanophthalmos, ROP, PHPV

10. Iris or ciliary body mass lesion

11. Open angle glaucoma.


Management


Management Goals

• Identification of patients at risk of developing primary angle closure (PAC) glaucoma or to identify patients with PAC

• To manage an acute attack

• To prevent permanent damage to angle of anterior chamber

• To ensure that patient leads a symptom free life


Management Goals

• To determine other mechanism of angle closure glaucoma than pupillary block

• To reverse or prevent angle closure by LASER PI or incisional iridectomy

• To determine residual angle closure after iridotomy

• To observe for chronic IOP elevation, progression of synechial angle closure / optic nerve damage and treat as indicated


MEDICAL THERAPY

Approaches

a. To reduce IOP

b. To relieve the angle closure


a. Reduction of IOP

• ORAL THERAPY

1. Acetazolamide

2. Glycerol

3. Isosorbid

• INTRAVENOUS THERAPY

1. Mannitol

2. Acetazolamide


a. Reduction of IOP

TOPICAL THERAPY

1. Beta-adrenergic blockers

2. Alpha 2 Adrenergic Agonist

3. Topical carbonic anhydrase inhibitor

4. Topical miotic


b. Relief of Angle Closure

1. Pilocarpine 1 or 2 %

2. Topical thymoxamine 0.5% (Eserine and Echothiopate Iodide are not indicated)

3. LASER PI

4. If not possible then surgical / incisional iridectomy

5. Lensectomy


Prophylactic Iridotomy

• Previously normal IOP is elevated• A potentially occludable angle is present• PAS that are attributable to episodes of angle

closure are present• There is progressive narrowing of the angle• Medication is required that may provoke

pupillary block• Symptoms are present that suggest prior angle

closure


Prophylactic Iridotomy

• The patient's occupation/avocation makes it difficult to access immediate ophthalmic care (e.g., the patient travels frequently to developing parts of the world or works on a merchant vessel).

• For the fellow eye in patients who have had an attack of acute PAC (as described in the section about “acute primary angle closure” under Orientation).


Follow-up Protocol

• Follow up to evaluate

a. Patency of Iridotomy

b. IOP measurement

c. Gonioscopy

d. Pupillary dilatation to decrease risk of posterior synechiae

f. Fundus examination


Follow up Protocol

• Patient should be examined to evaluate history and ocular examination at one week to 4 months if target IOP has been achieved but if damage is progressive every 3 months to every 12 months if target IOP has been achieved and no progressive damage.


Follow up Protocol

• If target IOP has not been achieved then patient should be followed up frequently

• Optic Disc should be evaluated after every 2 –12 months interval and visual field should be checked every 1 to 6 months depending on achieving target IOP


Counseling

• Patient at risk may be warned about taking decongestants, motion sickness medication and Anticholinergic agents. Patients should be informed about symptoms of acute angle closure glaucoma and to consult Ophthalmologist immediately if symptoms occur.