Glaucoma

Question 1

Where is aqueous humour made in the eye?

Answer 1

The ciliary body

Question 2

What is glaucoma?

Answer 2

A pathology where damage is sustained to the optic nerve due to raised intraocular pressure

Question 3

Where is the aqueous humour stored?

Answer 3

In the anterior and posterior chambers of the eye

Question 4

What is the pathway of the aqueous humour?

Answer 4

Made by ciliary body

Around lens under iris through anterior chamber, through trabecular meshwork into the canal of schlemm.

Enters general circulation and is reabsorbed into the body

Question 5

What is a normal intraocular pressure?

Answer 5

10-21mmHg

The pressure is created by resistance to flow through the trabecular meshwork

Question 6

Pathophysiology of open angle glaucoma?

Answer 6

Gradual increase in resistance through the trabecular meshwork leading to a gradual increase in intraocular pressure.

Question 7

Pathophysiology of closed angle glaucoma?

Answer 7

Iris bulges forward and seals off trabecular meshwork from the anterior chamber preventing aqueous humour from draining.

This leads to rapid build up in pressure - ophthalmological emergency

Question 8

Optic disc changes in open angle glaucoma?

Answer 8

Cupping of the optic disc. There is an increase in size of the optic cup compared to the disc. >50% of the size of the disc, this is abnormal.

Question 9

Risk factors for open angle glaucoma?

Answer 9

Increasing age

Family history

Myopia

Black ethnic origin

Question 10

Clinical presentation of open angle glaucoma?

Answer 10

Asymptomatic for a long period of time. Usually diagnosed by routine screening.

Peripheral vision affected first - gradual loss of peripheral vision leading to tunnel vision in later stages.

Fluctuating pain

Headaches

Haloes surrounding lights - worse at night time.

Question 11

How do you measure intraocular pressure?

Answer 11

1) Non-contact tonometry - shooting a puff of air at the cornea and measuring the corneal response to that puff of air. Increased pressure leads to reduced reaction of the cornea.
2) Goldmann applanation tonometry - gold standard method. Device mounted on slip lamp which makes contact with cornea and applies different pressures onto the eye to measure corneal response.

Question 12

How do we make a diagnosis of glaucoma?

Answer 12

Goldmann applanation tonometry

Fundoscopy

Visual field assessment - check for peripheral vision loss

Question 13

Medical management of open angle glaucoma?

Answer 13

Treatment started if IO pressure is >24mmHg

1) Prostaglandin analogues - e.g. Latanoprost. This increases uveoscleral outflow.
2) Topical beta blockers (e.g. Timolol - reduce production of humour)
3) carbonic anhydrase inhibitors (e.g. Dorzolamide - reduce production of humour)
4) sympathomimetrics (e.g. Brimonidine - reduce humour production, increase uveoscleral outflow)

Question 14

Side effects of topical prostaglandins?

Answer 14

Eyelash growth

Eyelid pigmentation

Iris pigmentation (browning of iris)

Question 15

Surgical procedure for open angle glaucoma?

Answer 15

Trabeculectomy - only if eyedrops are ineffective

New channel from anterior chamber through sclera to a location under the conjunctiva.

A bleb is created where the aqueous humour drains

Question 16

What is acute angle closure glaucoma?

Answer 16

Iris bulges forward and seals off trabecular meshwork from anterior chamber. This prevents aqueous humour from being able to drain away through the trabecular meshwork.

Question 17

In closed angle glaucoma, in what anatomical location does aqueous humour increase and worsen the presentation?

Answer 17

In the posterior chamber of the eye behind the iris

Question 18

What are the risk factors for acute angle closure glaucoma?

Answer 18

Increasing age

Females (4:1)

Family history

Chinese/East Asian ethnic origin

Shallow anterior chamber (anatomical variants)

Medication - e.g. Noradrenaline, anticholinergics and TCA’s.

Question 19

Clinical presentaiton of acute angle closure glaucoma?

Answer 19

SCROLL

Generally unwell

Orbital pain worsened on pressure

Red and tearing eye

Blurred vision

Haloes around lights

Associated headache, nausea and vomiting

Hazy cornea

Decreased visual acuity

Dilated pupil

Question 20

Management of acute angle closure glaucoma in the community?

Answer 20

Referred for same day assessment with ophthalmologist form primary care

Lie patient flat without pillow

Give Pilocarpine eye drops

Acetazolamide 500mg PO if available

Analgesia and antiemetics

Question 21

What does miosis mean?

Answer 21

pupillary contraction.

Question 22

Mechanism of action of pilocarpine?

Answer 22

Miotic agent - constricts pupils

Ciliary muscle contraction

Both mechanisms open the angle and drain aqueous humour from the eye

Question 23

Acetazolamide mechanism of action?

Answer 23

Carbonic anhydrase inhibitor - reduces production of aqueous humour production

Question 24

Management of acute angle closure glaucoma in secondary care?

Answer 24

Definitive treatment: Laser iridotomy

Pilocarpine

Acetazolamide

hyperosmotic agents - e.g. Glycerol or mannitol

Beta blockers - e.g. Timolol - reduces aqueous humour production

Sympathomimetics - reduce aqueous humour production