Open angle Glaucoma

Question 1

What is glaucoma?

Answer 1

Optic neuropathy with death of many retinal ganglion cells and their optic nerve axons
IOP may be raised.

they can be classified based on whether the peripheral iris is covering the trabecular meshwork which is important for the drainage of aqueous humour from the anterior chamber of the eye.
In open-angle glaucoma the iris is clear of the meshwork.

The trabecular network functionally offers an increased resistance to aqueous outflow causing increased IOP.

Question 2

What are risk factors for POAG?

Answer 2

Increasing age >35
Genetics - FHx
Black patients
Myopia
Hypertension
DM
Corticosteroids

High risk groups get free screening - screening is important as patients are symptomatic until visual field changes become very advanced

Question 3

What are features of POAD?

Answer 3

Peripheral visual field loss - nasal scotomas progressing to tunnel vision
Decreased visual acuity
Optic disc cupping

Typically present following ocular pressure measurement during a routing examination by an optometrist

Question 4

What are fundoscopy signs of POAG?

Answer 4

Optic disc cupping - cup to disc ratio >0.7
(normal =0.4-0.7)
- Occurs as loss of disc substance makes optic cup widen and deepen
- Large optic cup in small disc is probably pathological.

Optic disc pallor (optic atrophy)

Bayonetting of vessels
- As damage progresses the disc pales and the cup widens and deepens so vessels emerging from the disc appear to have breaks as they disappear into the cup and are seen at the base again.

Cup notching - usually inferior where the vessels enter the disc

Question 5

How is POAG diagnosed?

Answer 5

IOP measurement using tonometry
Central corneal thickness measurement
Peripheral anterior chamber configuration and depth assessments using gonioscopy
Visual field measurement
Optic nerve assessment using a slit lamp + pupil dilation with fundus examination
Automated perimetry to assess the visual field

Question 6

What is the aim of management in POAG?

Answer 6

Reduce intraoccqular pressure by 30% of baseline

Pharmacological and surgical management

Question 7

What is the first line treatment for POAG?

Answer 7

Prostaglandin analogue eye drops - Latanoprost

• Increase uveoscleral outflow
• OD
• ADR - brown pigmentation of iris

Question 8

What is second line for POAG?

Answer 8

BEta blockers (timolol 0.25-0.5%)
BD
Reduce production of aqueous
Avoid in asthma or heart failure - systemic absorption occurs without 1stPM

Alpha agonists (brimonidine, apraclonidine)
Reduce production of aqueous and increase uveoscleral outflow
ADR - lethargy, dry mouth

Carbonic anhydrase inhibitors (dorzolamide, brinzolamide drops, acetazolamide PO)
Reduce aqueous production
Avoid if pregnant
ADR of acetazolamide: lassitude, dyspepsia, hypokalaemia, paraesthesia)

Miotics (pilocarpine - muscarinic agonist)
Increase uveolsacral outflow
Causes mitosis , reduced visual acuity and headache from ciliary muscle spasm.

Question 9

What can be used if pharmacological management fails?

Answer 9

Laser therapy - trabeculoplasty - increased aqueous outflow, reduced IOP

Surgery trabeulectomy is a filtration surgery that establishes a pressure valve at the limbus so aqueous can flow into a conjunctival bleb.