Glaucoma

Question 1

What are the three layers of the eye?

Answer 1

1. Retina (neural layer)
2. Choroid (vascular layer): choroid + ciliary body and iris forming the uvea
3. Sclera (fibrous layer, continuous with the cornea)

Question 2

What are the different segments involving the eye?

Answer 2

• Anterior segment in front of the lens, containing aqeuous humour
• Posterior segment behind the lens containing vitreous humour

Question 3

Describe the different chambers that contains the aqueous humour.

Answer 3

There is anterior chamber between the cornea and the iris, and posterior chamber between the iris and the lens.

Question 4

How is aqueous humour produced and how does it flow?

Answer 4

Aqueous humour is produced by the ciliary epithelium in the ciliary body.

There is conventional trabecular outflow (90%) which travels between the lens in the posterior chamber through the pupil into the anterior chamber.

Aqueous humour then drains into the trabecular meshwork located at the angle between the cornea and the iris, canal of Schlemm, into aqueous veins and episcleral veins.

There is uveoscleral outflow (10%) where aqueous humour travels straight through ciliary muscle to the scleral surface.

Question 5

What is pathophysiology of glaucoma?

Answer 5

There is blockage to the trabecular meshwork, and aqueous humour builds up in the anterior chamber causing increasing pressure transmitted to the posterior segment. There is intraocular HTN and damage of optic nerves posteriorly.

Question 6

Open angle glaucoma

Pathophysiology?

Answer 6

Angle between cornea and iris is normal.
There is either:
1. Overproduction of aqueous humour OR
2. Obstruction to drainage via trabecular meshwork

There is gradual loss of vision from peripheral to central. Patients don’t have any other symptoms so it’s late presentation.

Question 7

Closed angle glaucoma

Pathophysiology?

Answer 7

Angle between cornea and iris is narrow. The iris comes in contact with the lens. Depending on the extent of angle closure, there is reduced or complete obstruction of outflow of aqueous humour into anterior chamber of the eye and any fluid that does not enter anterior chamber cannot drain out through the trabecular meshwork due to obstruction by the iris.

This increases IOP and leads to optic nerve damage.

Question 8

How does closed-angle glaucoma acutely present?

Answer 8

Acutely, there is severe eye pain, redness of the eye, mildly dilated pupil, blurred vision and nausea.

Question 9

Which is more common?

A. Open angle glaucoma
B. Closed angle glaucoma

Answer 9

Answer: A. Open angle glaucoma

It occurs in 90% of the cases, and closed angle glaucoma occurs in 10% of the cases.

Question 10

Which is more acute?

A. Open angle glaucoma
B. Closed angle glaucoma

Answer 10

Answer: B. Closed angle glaucoma

Open angle glaucomas tend to be more chronic and progressive due to its lack of symptoms.

Question 11

What is normal tension glaucoma?

Answer 11

No increase in IOP, and iridocorneal angle is normal with no impaired drainage of aqueous humour.

There is some damage to optic nerve, and it is believed to be as result of a vascular compromise to the optic nerve (associated with diabetes and metabolic syndromes). Management is the same as other glaucomas.

Question 12

What are some examples of secondary glaucoma?

Answer 12

1. Diabetes-related neovascularisation
2. Surgical/trauma
3. Drug-induced (e.g. corticosteroids)
4. Uveitis

Question 13

What are risk factors of glaucoma?

Answer 13

• Underlying IOP HTN
• FHx of glaucoma
• Age
• Race (African people more common)
• Myopia
• Diabetes
• HTN
• Migraine