Ophthalmology - Open-Angle Glaucoma

Question 1

What does glaucoma refer to?

Answer 1

Optic nerve damage caused by a rise in intraocular pressure

Question 2

What causes raised intraocular pressure in glaucoma?

Answer 2

A blockage in aqueous humour trying to escape the eye

Question 3

Name the types of glaucoma

Answer 3

• Open-angle glaucoma
• Acute angle-closure glaucoma
• Normal-tension glaucoma (rare- caused by hypoperfusion)

Question 4

What is the vitreous chamber of the eye filled with?

Answer 4

Vitreous humour

Question 5

What are the two chambers filled with aqueous humour?

Answer 5

• Anterior chamber (between the cornea and iris)
• Posterior chamber (between the lens and iris)

Question 6

What is the function of aqueous humour?

Answer 6

Supplies nutrients to the cornea

Question 7

What produces aqueous humour?

Answer 7

Ciliary body

Question 8

Where does aqueous humour flow?

Answer 8

Through posterior chamber

Around iris to anterior chamber

Then drains through the trabecular meshwork to the canal of Schlemm

Aqueous veins (part of the episcleral venous system)

Question 9

What is the normal range for intraocular pressure?

Answer 9

10-21 mmHg

Created by resistance to flow through the trabecular meshwork

Question 10

Label the diagrams

Answer 10

Question 11

What causes the gradual open-angle glaucoma?

Answer 11

Gradual increase in resistance to flow through the trabecular meshwork

Pressure slowly builds up within eye

Question 12

What happens in acute angle-closure glaucoma?

Answer 12

The iris bulges forward, sealing off the trabecular meshwork, preventing drainage

Continual build-up of pressure and acute symptom onset

Ophthalmological emergency

Question 13

What does raised intraocular pressure lead to?

Answer 13

Cupping of the optic disc

In the centre of the optic disc there is an indent - optic cup

Question 14

What causes cupping in glaucoma?

Answer 14

Pressure on optic nerve causing thinning of the outer nerve

Question 15

What is the cup-disk ratio considered abnormal?

Answer 15

Greater than 0.5.

Question 16

List risk factors for open-angle glaucoma

Answer 16

• Increasing age
• Family history
• Black
• Myopia (nearsightedness)

Question 17

How does glaucoma present?

Answer 17

Gradual onset of peripheral vision loss (tunnel vision) (due to gradual onset of outer nerve atrophy)
- Fluctuating pain
- Headaches
- Blurred vision
- Halos around lights, particularly at night

Question 18

What causes halos around lights in glaucoma?

Answer 18

Acute closed angle glaucoma

Spike in intraocular pressure leads to intracorneal oedema

Corneal endothelial cells pump aqueous humour out of the cornea and become unable to compete with the high pressure pushing the fluid into cornea

Cornea fills with AqH, leading to temporary loss of visual acuity, halos form around sources of light due to increased dispersion of light

Open angle glaucoma
Night-time
Iris moves as the pupils dilate to allow more light in at night, further reducing ability of AqH to drain (also during raised adrenalin activities)

Causes increases dispersion of light

Question 19

How is intraocular pressure measured?

Answer 19

Non-contact tonometry

Puff of air shot at cornea and corneal response measured

Question 20

What is the gold-standard method for measuring intraocular pressure?

Answer 20

Goldmann applanation tonometry

Slip lamp makes contact with cornea and applies pressure

Question 21

What are the key components of glaucoma diagnosis?

Answer 21

• Goldmann applanation tonometry for intraocular pressure
• Slit lamp assessment for cup-disk ratio and optic nerve health
• Visual field assessment for peripheral vision loss
• Gonioscopy to assess the angle between the iris and cornea
• Central corneal thickness assessment

Question 22

At what intraocular pressure is treatment typically started?

Answer 22

24 mmHg or above.

Question 23

What is 360° selective laser trabeculoplasty used for?

Answer 23

Improving drainage of aqueous humour

Laser is directed at trabecular meshwork, can delay or prevent need for eye drops

Used for all patients

Question 24

What are the first-line medical treatment eye drops for glaucoma?

Answer 24

Prostaglandin analogue eye drops (e.g., latanoprost)

Increases uveoscleral outflow

Question 25

Name notable side effects of prostaglandin analogue eye drops.

Answer 25

• Eyelash growth
• Eyelid pigmentation
• Iris pigmentation (browning)

Question 26

What other eye drop options can be used in glaucoma?

Answer 26

Beta-blockers
- Reduces aqueous humour production
- Timolol

Carbonic anhydrase inhibitors
- Reduces aqeuous humour production
- Dorzolamide

Sympathomimetics
- Reduces aqeuous humour production
- Increases uveoscleral outflow
- Brimonidine

Question 27

What surgical procedure may be required if other treatments are ineffective?

Answer 27

Trabeculectomy

Question 28

What does trabeculectomy surgery involve?

Answer 28

Creating a new channel from the anterior chamber through the sclera to a location under the conjunctiva causing a bleb on the conjunctiva

The reasborbed into general circulation