Glaucoma

Question 1

What is the pathophysiology of open angle glaucoma?

Answer 1

Increased resistance to aqueous outflow through the trabecular meshwork
Pressure-induced strain and stress results in compression and remodelling of lamina –> axonal damage

Question 2

What is the weakest point in the wall of the pressurised eye?

Answer 2

Lamina cribrosa - mesh-like structure at the optic nerve head that surrounds the retinal ganglion cell axons

Question 3

Why do some people have glaucomatous optic neuropathy when IOP is in normal range?

Answer 3

Could be due to an abnormally low CSF pressure in optic nerve subarachnoid space
Resulting in a large pressure gradient across the lamina

Question 4

What is the range for normal IOP?

Answer 4

10-21 mmHg

Question 5

How does glaucoma present?

Answer 5

Progresses asymptomatically until disease is so advanced that marked vision loss occurs

Question 6

What is the fundoscopic appearance of glaucoma?

Answer 6

Increased cup to disc ratio (cup increases in size)

Question 7

How do prostaglandin analogues work?

Answer 7

Increase uveoscleral outflow of aqueous humour

eg latanoprost, bimatoprost, tafluprost

Question 8

How do b-adrenergic blockers work?

Answer 8

Reduce aqueous humour production

eg timolol, betaxolol, carteolol

Question 9

How do a-adrenergic agonists work?

Answer 9

Initially reduce aqueous humour production which subsequently causes an increase in outflow
eg brimonidine

Question 10

How do carbonic anhydrase inhibitors work?

Answer 10

Reduce aqueous humour production

eg dorzolamide, acetazolamide

Question 11

How do cholinergic agonists work?

Answer 11

Increase aqueous humour outflow

eg pilocarpine

Question 12

How does laser trabeculoplasty treat glaucoma?

Answer 12

Induces biological changes in the trabecular meshwork resulting in increased aqueous outflow

Question 13

How do trabeculectomies treat glaucoma?

Answer 13

Excision of a portion of the trabecular meshwork

This provides a drainage route for aqueous humour to travel under the conjunctiva where it can be absorbed

Question 14

What is the pathophysiology of closed angle glaucoma?

Answer 14

The angle is obstructed by apposition of the iris (defined as at least 270 degrees of the angle being occluded)
NB angle is site of aqueous outflow

Question 15

How does acute angle closure present?

Answer 15

Very high IOP >30 mmHg
Red eye
Mid-dilated unresponsive pupil
Pain, nausea, haloes

Question 16

What causes closed angle glaucoma?

Answer 16

Pupillary block - resistance to aq humour flow from posterior to anterior chambers at the pupil
Other iris, lens and retrolenticular disorders

Question 17

How do you view the angle on examination?

Answer 17

Gonioscopy

Question 18

How is closed angle glaucoma treated?

Answer 18

Laser peripheral iridotomy (hole in iris to eliminate pupillary block)
If IOP remains high, long-term medical treatment (similar to open-angle) can be commenced

Question 19

What are some risk factors for glaucoma?

Answer 19

Smoking
PMH of obesity, hypertension, diabetes
Age >60
Afro-caribbean ethnicities
Corticosteroid use
FH