GLAUCOMA

By

Mohammed Fotouh El-Ashri

Msc, MD, FICO

Defenition

• Optic neuropathy
• IOP
• Field defect

INTRODUCTION TO GLAUCOMA

• Anatomy

1. Aqueous outflow

• Physiology

3. Tonometers

4. Gonioscopy

5. Anatomy of retinal nerve fibres

6. Optic nerve head

7. Humphrey perimetry

Aqueous outflow

Anatomy

a - Uveal meshwork

b - Corneoscleral meshwork

c - Schwalbe line

d - Schlemm canal

e - Collector channels

f - Longitudinal muscle of

ciliary body

g - Scleral spur

c - Iris outflow

70 process

BAB

a - Conventional outflow 80%

b - Uveoscleral outflow 15%

Physiology

• Function of Aqueous:

1- IOP

2- Metabolic

• Composition of Aq.

1- BAB

2- Small molecular wt amino acids

​

Tonometers

Goldmann

Contact applanation

Perkins

Portable contact applanation

Pulsair 2000 (Keeler)

Air-puff

Schiotz

Portable non-contact applanation

Non-contact indentation

Contact indentation

Tono-Pen

portable contact applanation

Goniolenses

Goldmann

• Single or triple mirror

Zeiss

• Contact surface diameter 12 mm

• Coupling substance required

• Four mirror

• Coupling substance not required

• Contact surface diameter 9 mm

• Suitable for ALT

• Not suitable for indentation gonioscopy

• Suitable for indentation gonioscopy

• Not suitable for ALT

Indentation gonioscopy

Differentiates ‘appositional’ from ‘synechial’ angle closure

Press Zeiss lens posteriorly

against cornea

Aqueous is forced into

periphery of anterior chamber

Indentation gonioscopy in iridocorneal contact

• Part of angle is forced open

During indentation

• Part of angle remains closed by PAS

• Complete angle closure

Before indentation

• Apex of corneal wedge not visible

Angle structures

Schwalbe line

Schlemm canal

Trabeculum

Scleral spur

Iris processes

Shaffer grading of angle width

• Ciliary body easily visible

Grade 4 (35-45 )

• At least scleral spur visible

Grade 2 (20 )

Grade 3 (25-35 )

Grade 1 (10 )

• Only trabeculum visible

• Only Schwalbe line and perhaps

top of trabeculum visible

• High risk of angle closure

• Iridocorneal contact present

• Apex of corneal wedge not visible

• Angle closure possible but unlikely

• Use indentation gonioscopy

3

2

1

0

4

Grade 0 (0 )

Anatomy of retinal nerve fibres

Horizontal

raphe

Papillomacular

bundle

Optic nerve head

a - Nerve fibre layer

Small physiological cup

b - Prelaminar layer

c - Laminar layer

• Normal vertical cup-disc ratio is 0.3 or less

• 2% of population have cup-disc ratio > 0.7

• Asymmetry of 0.2 or more is suspicious

Total glaucomatous cupping

Large physiological cup

a

c

b

Types of physiological excavation

Small dimple central cup

Larger and deeper

punched-out central cup

Cup with sloping temporal

wall

Pallor and cupping

Cupping and pallor correspond

Pallor - maximal area of colour contrast

Cupping is greater than pallor

Cupping - bending of small blood vessels crossing disc

Methods of field examination:

• Confrontation test
• Light projection
• Amsler chart
• Perimetry; Static, Kinetic

​

Humphrey perimetry

Reliability Indices

• Detected by presenting stimuli in blind spot

1. Fixation losses

• Stimulus accompanied by a sound

• High score suggests a ‘trigger happy’ patient

• Failure to respond to a stimulus 9 dB brighter than previously seen at

same location

• High score indicates inattention, or advanced field loss

3. False negatives

2. False positives

Deviations

• Upper numerical display shows difference (dB) between

patient’s results and age-matched normals

1. Total

• Lower graphic display shows these differences as grey scale

• Similar to total deviation

2. Pattern

• Adjusted for any generalized depression in overall field

Global Indices

• Deviation of patient’s overall field from normal

1. Mean deviation (elevation or depression)

• p values are < 5%, < 2%, < 1% and < 0.5%

• The lower the p value the greater the significance

• Consistency of responses

3. Short-term fluctuation

• 2 dB or less indicates reliable field

• > 3 dB indicates either unreliable or damaged field

• Departure of overall shape of patient’s hill of vision from

age-matched normals

4. Corrected pattern standard deviation

• Departure of visual field from age-matched normals

2. Pattern standard deviation

1. Pathogenesis

3. Intermittent

2. Classification

4. Acute congestive

PRIMARY ANGLE-CLOSURE GLAUCOMA

5. Post congestive

6. Chronic

Anatomical predispositions

• Convex iris-lens

diaphragm

• Shallow anterior

chamber

• Narrow entrance to

chamber angle

Pupil block

• Increase in physiological

pupil block

• Dilatation of pupil renders peripheral

iris more flaccid

• Increased pressure in posterior

chamber causes iris bombe

• Angle obstructed by peripheral iris

and rise in IOP

1. Latent - asymptomatic

3. Acute

2. Subacute - intermittent angle closure

4. Chronic - ‘creeping or latent’ angle closure

• IOP may remain normal

• May progress to subacute, acute or chronic

angle closure

• May develop acute or chronic angle closure

• Congestive - sudden total angle closure

• Postcongestive - follows acute attack

• Follows intermittent angle closure

5. Absolute

Classification

• No PL following acute attack

Intermittent angle-closure glaucoma

• Treatment - bilateral YAG laser

iridotomy

• Epithelial oedema and closed angle

during attack

Signs

Treatment

Acute congestive angle-closure glaucoma

• Severe corneal oedema

• Complete angle closure

(Shaffer grade 0)

• Dilated, unreactive,

vertically oval pupil

• Shallow anterior

chamber

• Ciliary injection

Signs

Treatment of Acute Congestive

Angle-Closure Glaucoma

2. Hyperosmotic agents - if appropriate

• Oral glycerol 1-1.5 g/kg of 50% solution in lemon juice
• Intravenous mannitol 2g/kg of 20% solution

3. Topical therapy

• Pilocarpine 2% to both eyes
• Beta-blockers
• Steroids

1. Acetazolamide 500 mg i.v.

4. YAG laser iridotomy

• To both eyes when cornea is clear

Signs of postcongestive angle-closure glaucoma

• Folds in Descemet

membrane

• Stromal iris atrophy with

spiral-like configuration

• Posterior synechiae

• Fixed dilated pupil

• Fine pigment on iris

• Glaukomflecken

Chronic angle-closure glaucoma

• Similar to POAG with

cupping and field loss

• Easily missed unless routine

gonioscopy performed

• Variable amount of angle closure

Signs

Definition and risk factors

IOP > 21 mmHg

Glaucomatous disc damage

Open angle of normal appearance

Visual field loss

Risk Factors

1. Age - most cases present after age 65 years

2. Race - more common, earlier onset and more

severe in blacks

3. Inheritance

• Level of IOP, outflow facility and disc size are inherited
• Risk is increased by x2 if parent has POAG
• Risk is increased x4 if sibling has POAG

4. Myopia

Theories of glaucomatous damage

Direct damage by pressure

Capillary occlusion

Interference with

axoplasmic flow

Early visual field defects

• Small arcuate scotomas

• Tend to elongate circumferentially

• Isolated paracentral scotomas

• Nasal (Roenne) step

Progression of visual field defects

• Formation of arcuate defects

• Enlargement of nasal step

• Development of temporal wedge

• Peripheral breakthrough

• Appearance of fresh arcuate

inferior defects

Advanced visual field defects

• Development of ring scotoma

• Peripheral and central spread

• Residual temporal island

• Residual central island

Drugs to treat glaucoma

1. Beta blockers

2. Sympathomimetics

3. Miotics

4. Prostaglandin analogues

5. Carbonic anhydrase inhibitors

• Topical
• Systemic

Laser trabeculoplasty

• Failed medical therapy

Indications

• Primary therapy in non-compliant patients

to junction of pigmented and

non-pigmented trabeculum

• Correct focus with round

aiming beam

• Incorrect focus with oval

aiming beam

• Application of 50-100 burns

Indications for Trabeculectomy

1. Failed medical therapy and laser trabeculoplasty

• Inability to adequately visualize trabeculum

3. As primary therapy in advanced disease

• Poor patient co-operation

2. Lack of suitability for trabeculoplasty

Technique (1)

a. Conjunctival incision

b. Conjunctival undermining

d. Outline of superficial flap

e. Dissection of superficial flap

f. Paracentesis

c. Clearing of limbus

f

d

b

a

c

e

a. Cutting of deep block -

anterior incision

b. Posterior incision

d. Peripheral iridectomy

e. Suturing of flap and

reconstitution of

anterior chamber

f. Suturing of conjunctiva

c. Excision of deep block

f

d

b

a

c

e

Technique (2)

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