Glaucoma

Question 1

What is the pathophysiology of glaucoma?

Answer 1

Optic nerve damage caused by a rise in intraocular pressure. Raised pressure is caused by a blockage in aqueous humour trying to leave the eye.

Question 2

What is the pathway of aqueous humour?

Answer 2

1. Produced by ciliary body.
2. Flows around lens and under iris.
3. Flows through anterior chamber and trabecular meshwork and into canal of Schlemm.
4. Eventually enters general circulation.

Question 3

What is the normal intraocular pressure and what causes it?

Answer 3

10-21 mmHg, resistance to flow through trabecular meshwork into canal of Schlemm.

Question 4

What is the pathophysiology of open angle glaucoma?

Answer 4

Gradual increase in resistance of trabecular meshwork, more difficult for aqueous humour to exit eye, pressure build-up (slow and chronic).

Question 5

What is the pathophysiology of acute angle-closure glaucoma?

Answer 5

Iris bulges forward and seals off trabecular meshwork from anterior chamber preventing aqueous humour leaving eye. Continual build-up of pressure. Emergency.

Question 6

What is the effect of glaucoma on the optic disc?

Answer 6

Causes disc cupping, abnormal if cup becomes greater than 0.5 the size of disc.

Question 7

What are the risk factors for open angle glaucoma?

Answer 7

Increasing age, family history, black ethnic origin, near-sightedness (myopia).

Question 8

What is this a presentation of:
Routine screening diagnosis, peripheral vision affected first, gradual tunnel vision, fluctuating pain, headaches, blurred vision, halos around lights?

Answer 8

Open angle glaucoma

Question 9

What are the two methods of measuring intraocular pressure and how do they work?

Answer 9

1. Non-contact tonometry - shoots air at cornea and measures corneal response, less accurate.
2. Goldmann applanation tonometry - gold standard, device on slit-lamp that contacts cornea and applies different pressures for accurate measurement.

Question 10

How is open angle glaucoma diagnosed?

Answer 10

1. Goldmann applanation tonometry - for intraocular pressure
2. Fundoscopy - optic disc cupping and optic nerve health
3. Visual field assessment - peripheral vision loss

Question 11

What are the medication options for glaucoma?

Answer 11

1. Prostaglandin analogue eye drops - latanoprost, started at 24mmHg
2. Beta-blockers - timolol
3. Carbonic anhydrase inhibitors - IV acetazolamide, dorzolamide
4. Sympathomimetics - brimonidine

Question 12

How does latanoprost work on the eye and what are it’s side effects?

Answer 12

Increase uveoscleral outflow to lower intraocular pressure.

Eyelash growth, eyelid pigmentation, iris pigmentation.

Question 13

How do timolol/dorzolamide/brimonidine work on the eye?

Answer 13

They all reduce production of aqueous humour.

Brimonidine also increases uveoscleral outflow.

Question 14

What is the surgical technique used in open angle glaucoma and what are the steps?

Answer 14

Trabeculectomy surgery (if eye drops ineffective)/

1. Creation of new channel from anterior chamber through sclera to location under conjunctiva.
2. Causes a ‘bleb’ under the conjunctiva where aqueous humour drains.
3. Then reabsorbed from this ‘bleb’ into general circulation.

Question 15

What are the risk factors for acute angle-closure glaucoma?

Answer 15

Increasing age, female, family history, Chinese/east Asian ethnic origin (rare in black ethnic origin), shallow anterior chamber, long-sightedness (hypermetropia).

Question 16

Which medications can predispose someone to getting acute angle-closure glaucoma?

Answer 16

1. Adrenergic - noradrenaline
2. Anticholinergic - oxybutynin and solifenacin
3. Tricyclic antidepressants - amitriptyline (anticholinergic effects)

Question 17

What is this a presentation of:
Generally unwell, severely painful red eye, blurred vision, halos around lights, associated headache, nausea, and vomiting?

Answer 17

Acute angle-closure glaucoma

Question 18

What do these findings on examination indicate:

Red eye, teary, hazy cornea, decreased visual acuity, semi-dilated non-reacting pupil, firm eyeball on palpation?

Answer 18

Acute angle-closure glaucoma

Question 19

What is the initial management of acute angle-closure glaucoma?

Answer 19

1. Lie patient on back without pillow.
2. Give pilocarpine eye drops
3. Give acetazolamide PO/IV
4. Give analgesia and antiemetic if required

Question 20

How does pilocarpine help glaucoma?

Answer 20

Acts on muscarinic receptors in sphincter muscles in the iris and causes pupil constriction, miotic agent.
Also causes ciliary muscle contraction and opens pathway for flow of aqueous humour.

Question 21

What is the definitive treatment for acute angle-closure glaucoma and what are the steps?

Answer 21

Laser iridotomy.

1. Laser makes a hole in the iris to allow aqueous humour to flow into anterior chamber.
2. Relieves the pressure that was pushing the iris against the cornea.