Glaucoma

Question 1

What is glaucoma?

Answer 1

A group of eye conditions that damage the optic nerve. Most commonly because of raised intraocular pressure.

Question 2

Types of glaucoma

Answer 2

Open angle (considering the iridocorneal angle)
Closed angle
Normal tension glaucoma
Secondary glaucoma (e.g. to diabetes or other vascular problems ; drugs)

Question 3

Normal physiology of outflow

Answer 3

Aqueous humour is produced in the ciliary epithelium.

Drainage: Posterior segment - anterior segment –> ciliary epithelium - trabecular meshwork –> canal of Schlemm –> aqueous veins –> episcleral veins

Outflow can be mechanical obstruction (closed angle) or open angle (dysfunctional outflow network)

Question 4

Investigations

Answer 4

Tonometry: measure IOP (normal 12-22mmHg)
Gonioscopy: measures the iriocorneal angle
Fundoscopy: visualise the optic disc cup:disc ratio (normal <0.3)
Slit Lamp: visualise the interior eye and see if there is any leakage of humour
Perimetry: visual fields assessment

Question 5

Pharmacological agent classes

Answer 5

Prostaglandin analogues 
Alpha-2 agonists 
Carbonic anhydrase inhibitors 
Cholinergics 
(Non-selective Beta blockers)

Question 6

MOA and adverse effects of Prostaglandin analogues

Answer 6

MOA: increase aqeous outflow through increasing sclera permeability

A/E: ocular - eyelash lengthening, iris hyperpigmentation ; systemic: flu-like symptoms, headache

Question 7

MOA and adverse effects of Alpha-2 agonists

Answer 7

MOA: reduce aqueous humour production, reduce sympathetic effects by reducing noradrenaline uptake, increases outflow

A/E: high allergy rate, lid retraction, pupil dilation, stinging

Question 8

MOA and adverse effects of carbonic anhydrase inhibitors

Answer 8

MOA: reduce bicarbonate availability for ciliary epithelium and subsequently reduce aqueous humour production

A/E: blepharoconjunctivitis, bitter taste, depression, anxiety

Question 9

MOA and adverse effects of cholinergics

Answer 9

MOA: Act on M3 receptors so that there is ciliary muscle contraction and mechanically openinig of the iridocorneal angle

A/E: reduced visual acuity because of ciliary spasm, bronchospasm, bradycardia

Question 10

Follow-up considerations

Answer 10

Remember to check tonometry, fundoscopy and perimetry.

Check for systemic side effects

Question 11

Tips to optimise medications and also reduce systemic complications

Answer 11

DOT x DOT
digital occulusion at the punctum
do not open the eyes 2-3 minutes after drops in!

Question 12

MOA and adverse effects of beta blockers?

Answer 12

Topical beta blockers reduce IOP by blockade of sympathetic nerve endings in the ciliary epithelium causing a fall in aqueous humour production. They can be nonselective, or cardioselective (beta 1 only).
Examples include timolol and levobunolol and betaxolol (cardioselective). They can also be combined with other glaucoma agents e.g. latanoprost/timolol (xalacom).

Most serious side effect is exacerbation of COPD and precipitation of bronchospasms