Glaucoma

Question 1

List the different types of glaucoma?

Answer 1

Primary:
Open Angle Glaucoma (including normal pressure glaucoma)
Closed Angle Glaucoma

This is referring to the degree of the angle between the lens and the iris.

Secondary (to numerous conditions).

Question 2

Define glaucoma and ocular hypertension?

Answer 2

Glaucoma is a optic nerve neuropathy characterised by an increasing cup/disc ratio and reduction in visual fields and acuity.

It is usually associated with raised intraocular pressure.

Raised intraocular pressure in the absence of these glaucomatous changes is known as ocular hypertension.

Question 3

Describe the major features of POAG, and the associated symptoms?

Answer 3

Characterised by:

• Increasing cup disk ratio (normal is usually between 0.3-0.5) –> optic nerve damage
• Visual field loss (nasal & superior first)
• Elevated pressure >21mmHg

No pain
It is a very slowly progressing disorder and due to this patients often do not report symptoms until there is a significant visual loss.

Question 4

Describe the aetiology of POAG?

Answer 4

Not fully understood but thought to be to age related decreasing function of the trabecular meshwork (reduced number of vesicles; drains via pinocytosis).

Therefore there is excess aqueous humour increasing the pressure which damages the optic nn.

Question 5

Describe the mechanism in acute angle glaucoma?

Answer 5

It is caused by obstruction of the aqueous humour outflow due to the iris closing the angle between it and the lens, this occurs when the pupil is dilated.

Due to the pressure building up behind the iris it can force it to bulge aka iris bombe; this closes the angle of the acute chamber reducing the drainage via the trabecular network.

Question 6

Describe the symptoms of acute angle glaucoma?

Answer 6

Red eye
Very painful
Rapid progressive reduction in vision

Fixed mid dilated pupil.
Severe cases nausea and vomiting.

Question 7

What are the risk factors for developing acute angle glaucoma?

Answer 7

Shallow anterior chamber.

Hypermetropic (long sighted) individuals. (small globes)

Question 8

What are the causes of secondary glaucoma?

Answer 8

Inflammatory: Uveitis
Neovascular: Secondary to diabetic retinopathy 
Pigment dispersion syndrome
Pseudoexfoliation
Traumatic Hyphaema

Question 9

Describe the treatment aim and the different medical and surgical treatments used for primary open angle glaucoma?

Answer 9

Aim: to reduce the IOP by 30%.

Medical:

Prostaglandin agonist: (Latanoprost) - Lowers IOP by increasing the uveoscleral outflow of aqueous humour. S/e: red puffy eyes, increase melanin deposition, increase the length of the eye lashes.

Beta Blocker eye drops: (Timolol) - decreases aqueous secretions. But contraindicated in heart failure, asthma, COPD.

Alpha adrenergic agonist: (brimonidine) - slows down production and increases outflow

Carbonic Anhydrase Inhibitors (dorzolamide) -
Carbonic Anhydrase catalyses the reaction converting bicarbonate and oxygen into water and CO2.
By inhibiting this reaction you decraese the amount of fluid decreasing the pressure.

Cholinergic (pilocarpine) - increases outflow

Surgery:

Laser Trabeculectomy: Make a hole between subconjunctival space and acute angle increasing drainage.

Question 10

Describe the management of primary angle closure glaucoma?

Answer 10

Medical emergency.

Miotic treatment pilocarpine (as it occurs during mydriasis).

Oral carbonic anhydrase inhibitors: acetazolamide

Treat opposite eye prophylactically.