Primary open-angle glaucoma

Question 1

What are glaucomas?

Answer 1

Optic neuropathies associated with raised intraocular pressure (IOP)

Glaucomas can be classified based on the position of the peripheral iris relative to the trabecular meshwork.

Question 2

How can glaucomas be classified?

Answer 2

Based on whether the peripheral iris covers the trabecular meshwork

This is important for the drainage of aqueous humour from the anterior chamber of the eye.

Question 3

What is primary open-angle glaucoma (POAG)?

Answer 3

A type of glaucoma where the iris is clear of the trabecular meshwork

In POAG, the trabecular network offers increased resistance to aqueous outflow, leading to increased IOP.

Question 4

What factors may indicate the presence of POAG?

Answer 4

Peripheral visual field loss, decreased visual acuity, optic disc cupping

Peripheral visual field loss may progress to ‘tunnel vision’.

Question 5

What is the normal cup-to-disc ratio?

Answer 5

0.4-0.7

A cup-to-disc ratio greater than 0.7 indicates optic disc cupping.

Question 6

What are some fundoscopy signs of POAG?

Answer 6

• Optic disc cupping
• Optic disc pallor
• Bayonetting of vessels
• Cup notching
• Disc haemorrhages

These signs indicate various structural changes in the optic disc.

Question 7

What is the role of an optometrist in glaucoma diagnosis?

Answer 7

Case finding and provisional diagnosis

Referral to an ophthalmologist is done via the GP.

Question 8

What investigations are performed for glaucoma diagnosis?

Answer 8

• Automated perimetry
• Slit lamp examination
• Applanation tonometry
• Central corneal thickness measurement
• Gonioscopy

These investigations assess visual field and measure IOP among other factors.

Question 9

What is the aim of glaucoma treatment?

Answer 9

To lower intra-ocular pressure

Lowering IOP helps prevent progressive loss of visual field.

Question 10

What is the first-line treatment for glaucoma according to NICE guidelines?

Answer 10

360° selective laser trabeculoplasty (SLT) for IOP of ≥ 24 mmHg

SLT can delay the need for eye drops.

Question 11

What are the next line treatments after SLT?

Answer 11

• Prostaglandin analogue (PGA) eyedrops
• Beta-blocker eye drops
• Carbonic anhydrase inhibitor eye drops
• Sympathomimetic eye drops
• Trabeculectomy (in refractory cases)

These medications aim to further reduce IOP.

Question 12

What is the mechanism of action of prostaglandin analogues?

Answer 12

Increases uveoscleral outflow

Example: Latanoprost, administered once daily.

Question 13

What should be avoided when prescribing beta-blockers?

Answer 13

Asthmatics and patients with heart block

Examples include timolol and betaxolol.

Question 14

What is a significant side effect of sympathomimetics?

Answer 14

Hyperaemia

Example: Brimonidine, which also reduces aqueous production.

Question 15

What adverse effects can carbonic anhydrase inhibitors cause?

Answer 15

Sulphonamide-like reactions

Example: Dorzolamide, which reduces aqueous production.

Question 16

What are the side effects of miotics?

Answer 16

• Constricted pupil
• Headache
• Blurred vision

Example: Pilocarpine, a muscarinic receptor agonist.

Question 17

True or False: A minority of patients with raised IOP do not have glaucoma.

Answer 17

True

Conversely, some patients with glaucoma may have normal IOP.

Question 18

What is the relationship between age and glaucoma prevalence?

Answer 18

Affects < 1.5% under 55 years, up to 10% over 80 years

Increasing age is a significant risk factor for glaucoma.

Question 19

What is the chance of first-degree relatives developing open-angle glaucoma?

Answer 19

16%

Genetics is a key risk factor for glaucoma.

Question 20

Fill in the blank: _______ is a risk factor for glaucoma associated with certain ethnicities.

Answer 20

Afro Caribbean ethnicity

This demographic shows increased prevalence of glaucoma.