Glaucoma

Question 1

Glaucoma

Answer 1

a condition characterised by optic disc cupping and visual field loss in which the intraoccular pressure is sufficiently raised to impair normal optic nerve function

Question 2

Type of glaucoma

Answer 2

Primary (unknown cause)
- primary open angle glaucoma (POAG)
- primary acute angle glaucoma
Secondary
- open/closed
- cause - inflammation, trauma, neurovascular, congenital

Question 3

occular hypertension

Answer 3

Raised IOP >21mmHg, but normal optic disc and visual field

Question 4

Primary open angle glaucoma (POAG)

Answer 4

syndrome of:

• raised IOP
• open aqueous humor drainage angle
• glaucomatous visual field loss (peripheral –> central)
• pathalogically cupped optic disc

Question 5

Pathogenesis of POAG

Answer 5

• direct mechanical theory - raised IOP mechanically damages optic nerve
• indirect ischamia theory - ischaemia to optic nerve due to raised IOP interfering with microcirculation and perfussion pressure is too low to compensate

Question 6

Causes of PAOG

Answer 6

ageing, corticosteroids, inherited (dominant)

Question 7

Associations with PAOG

Answer 7

• family history
• occular: high myopia, central retinal vein occlusion
• systemic e.g. DM

Question 8

drainage of aqueous humour

Answer 8

anterior chamber –> trabecular meshwork –> canal of schlemm –> retinal veins

Question 9

Symptoms of POAG

Answer 9

• usually asymptomatic, never painful
• white eye
• vision loss when condition advanced - doesn’t affect central vision till late on, you can lose a lot of your peripheral vision without realising

Question 10

POAG examination

Answer 10

• usually normal distance visual acuity
• raised IOP using the Goldmann aplantation tonometer
• open drainage angle on gonioscopy
• pathologically cupped optic disc (cup:disc ration >0.5), pallor, nasal shift of vessels
• visual field loss

Question 11

POAG complications

Answer 11

• retinal vein occlusion

- visual field loss: nasal –> superior and inferior scotoma’s –> temporal and central islands –> blind

Question 12

Measuring visual fields

Answer 12

• Goldmanns fields

- Humphrey fields (computerised version)

Question 13

What factors make occular hypertension more likley to progress to POAG

Answer 13

• age
• increased cup:disc ratio
• increased level of IOP
• decreased central corneal thickness

Question 14

Monitoring patients with glaucoma

Answer 14

Measure IOP
Optic disc
Visual fields

Question 15

Treatment sumary for POAG

Answer 15

Medical - reduce production of aqueous humour or increase drainage (outflow)
Surgical - increase drainage/outflow

Question 16

Topical medications for glaucoma

Answer 16

Increase drainage
- prostaglandin F2a analogues (e.g. latanoprost)
Reduce aqueous production
- B-blockers e.g. timilol
- Carbonic anhydrase inhibitors e.g. dorzolamide
Both
- alpha agonists - brimonidine

Question 17

Systemic medications for glaucoma

Answer 17

• temporary/emergency treatment due to systemic side effects

- carbonic anhydrase inhibitor - acetazolamide (reduce aqueous production)

Question 18

Surgery for glaucoma

Answer 18

• trabeculectomy - create passage from anterior chamber to subconjunctival space for aqueous humour to drain
• give topical chemotherapy at time of therapy to prevent scar formation