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INTRODUCTION TO GLAUCOMA

� Anatomy

1. Aqueous outflow

� Physiology

3. Tonometers

2. Classification of secondary glaucoma

4. Gonioscopy

5. Anatomy of retinal nerve fibres

6. Optic nerve head7. Humphrey perimetry

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Aqueous outflow

Anatomy

a - Uveal meshwork 

b - Corneoscleral meshwork c - Schwalbe line

d - Schlemm canale - Collector channelsf - Longitudinal muscle of 

ciliary bodyg - Scleral spur

c - Iris outflow

a - Conventional outflow

b - Uveoscleral outflow

Physiology

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Classification of secondary glaucomas

a. Pre-trabecular - membrane overtrabeculum

Open-angle

b. Trabecular - µclogging up¶ of trabeculum

c. With pupil block - seclusio pupillae andiris bombé

Angle-closure

d. Without pupil block - peripheral anteriorsynechiae

c d

a b

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Tonometers

GoldmannContact applanation

PerkinsPortable contact applanation

Pulsair 2000 (Keeler)Air-puff 

Schiotz

Portable non-contact applanationNon-contact indentation

Contact indentation

Tono-Pen

portable contact applanation

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GoniolensesGoldmann

� 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

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Indentation gonioscopy

Differentiates µappositional¶ from µsynechial¶ angle closure

Press Zeiss lens posteriorlyagainst cornea

Aqueous is forced intoperiphery of anterior chamber

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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

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Angle structures

Schwalbe line

Schlemm canal

Trabeculum

Scleral spur

Iris processes

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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 perhapstop 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

04

Grade 0 (0 )

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Optic nerve head

a - Nerve fibre layerSmall 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

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Types of physiological excavation

Small dimple central cupLarger and deeperpunched-out central cup

Cup with sloping temporalwall

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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

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Humphrey perimetry

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Reliability Indices

� Detected by presenting stimuli in blind spot

1. Fixation losses

� Stimulus accompanied by a sound

� High score suggests a µtrigger 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

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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

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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 fromage-matched normals

4. Corrected pattern standard deviation

� Departure of visual field from age-matched normals2. Pattern standard deviation