15 - Glaucoma - Part 1

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By: noor majeed rehani

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Definition:y It is a heterogenous group of diseases in which

damage to the optic nerve(optic neuropathy) isusually caused by raised ocular pressure (normalIOP is 15.5 mmHg) acting on the nerve head.range(11-21)

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Basic physiology ofaqueous

humour:

1. Convent

ional pat

hway2. Uveo-scleral pathway

LOP: Depends on the balance betweenproduction and removal of aqueoushumour

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Aqueous humour is secreted by the ciliary processes in the

posterior chamber. Then it passes through the pupil into the

anterior chamber.

It is drained in posterior chamber through the Trabecular

meshwork, Schlemms canal, and episcleral veins.

1. Conventional Pathway:

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Supra-choroidal space

choroid

Drains a small proportion of aqueous (4%).

It drains it across the ciliary body into the supra-coroidal space,

and into the venous circulation across the sclera.

. Uveo-scleral pathway

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Mechanism of Optic nerve fiber

damagey Mechanical damageTo optic nerve axons bythe raisedIOP

y Ischemia of nerve fibers caused by impaired perfusionpressure (reducing blood flow at optic nerve head)

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Classification of Glaucoma:

1. Primary glaucoma:1. Chronic open angle

2. Acute and chronic closed angle

2. Congenital glaucoma:

1. Primary2. Rubella

3. Secondayto other inherited ocular disorders (e.g. an-iridia; absense of iris)

3. Secondary glaucoma (causes):

1. trauma2. Ocular surgery

3. Associated with other ocular diseases (uveitis)

4. Raised episcleral venous pressure

5. Steroid induced

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Primary Glaucoma:Is the iris:

Covering theTrabecular meshwork

NOT covering theTrabecular meshwork

OPEN angle glaucoma CLOSED angle glaucoma

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Primary OPEN angle glaucomay Pathogenesis:

y Resistance of drainage of aqueous through the

Trabecular meshwok, due to:1. Thickening of Trabecular lamellae (reduces pore

size).

2. Reduction in number of lining Trabecular cells.

3. Increased extracellular material in the Trabecularmeshwork spaces.

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Open irido-corneal angle(Trabecular meshwork is not covered)

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Primary OPEN angle glaucoma:yIt is the most common type of glaucom

y

It is the 3rd

cause of blindness in the UKyIt is also called chronic open angle

glaucoma.

yIt causes SLOWdamage to the opticnerve, causing gradual loss of vision.

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y The patient first loses the peripheral visual fieldthen it progress to total blindness if leftuntreated.

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As fluids accumulates in the anterior chamber due to

decreased drainage, intra-ocular pressure increases and

cases damage to the optic nerve.

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Primary OPEN angle glaucoma

(cont.)y Symptoms:1. Because the vision loss is gradual, the patient

usually present when severe damage has occurred.

2. Most patients are detected by optometrist routineexamination.

y Risk groups:

1. Affects 1 in 200 of population over the age of 40.

2. Males and females are equally affected.

3. The prevalence increase with age to nearly 10% inthe over 80 population.

4. There maybe family history butthe exact mode ofinheritance is not clear.

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Normal tension glaucoma:y Some open angle glaucoma have normal intra-ocular

pressure called low-tension or normal-tensionglaucoma.(glucomatous change)

y In these cases, there will be damage to the opticnerve even though the intra-ocular pressure is within

normal range.y The eyes ofthe normal tension glaucoma have

normal angles, so its features are similar to that ofprimary open angle glaucoma.

y The causes of normal tension glaucoma is stillunknown. The optic nerve is susceptible to damageeven from normal IOP.

y Normal-tension glaucoma is thoughtto be related, atleast in part, to poor blood flow to the optic nerve.

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Normal tension glaucoma (cont.):y Risk factors:

1. Family history of glaucoma.

2. Cardiovascular diseases.

Treatment:

1. Even though the IOP is normal but medication todecrease IOP as much as possible are used.

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Acute angle closure glaucoma:y The condition occurs in small eyes (as in hyperopoia)

with shallow anterior chambers.

yNormallythere is some resistance between the pupilmargin and the lens.

y But sometimes.

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Acute angle closure glaucoma (cont.):Acute angle closure glaucoma (cont.):

Sometimes when the iris is dilated, the lens sticks to the back of the

iris causing obstruction of fluid flow from posterior to anterior

chambers.

Fluid will accumulate behind the iris and pushes

it on to the Trabecular meshwork preventing

drainage of aqueous from the eye.

This causes rapid increase in IOP

.

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Acute angle closure glaucoma

(cont.):y Symptoms:

1. The eyes becomes red and painful due to rapid

increase in IOP.

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(cont.):2. Blurred vision; because the cornea becomes

edematous.

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(cont.):3. Patient may notice haloes (circles of light)around light due to dispersed light inwaterlogged cornea.

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(cont.):y They may have similar symptoms in the pastthat are aborted by going to sleep, becausesleeping constricts the pupils pulling it fromthe lens.

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End of first part.

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15 - Glaucoma - Part 1