Eye drainage system (aqueous)

Question 1

What is the vitreous humour made of?

Answer 1

A gelatinous mass held together by fine fibrils of elongated proteoglycan fibres
Sits behind lens and in front of retina

Question 2

What are the functions of the humours?

Answer 2

Keeps eyeball appropriately distended (maintains IOP)

Provides nutrition to avascular structures of the eye especially cornea and lens (aq)

Question 3

Which muscles are in the iris and control the size of the pupil?

Answer 3

Dilator pupillae

Sphincter pupillae

Question 4

What are the posterior and anterior parts of the ciliary body called?

Answer 4

Posterior = Pars plana
Anterior = pars plicata (folded)

Question 5

Which structure plays a major part in formation of aqueous humour?

Answer 5

Ciliary epithelium which lines folds of ciliary bodies

Folds are formed by vascular stroma

Question 6

How is aqueous humour formed?

Answer 6

Active transport of Na+ out of ciliary epithelial cells into posterior chamber
Followed by passive transport of Cl- and HCO3-into posterior chamber
Followed by H2O
Including glucose, amino acids and ascorbic acid (vit C)

Question 7

What are ciliary processes?

Answer 7

Projections of ciliary epithelium which actively secrete aqueous humour

Question 8

What is the ciliaris?

Answer 8

Muscle within ciliary body

Question 9

What rate is aqueous humour produced at?

Answer 9

2.5 ul / min

Question 10

Roughly what volume of aqueous humour is normally present in the posterior and anterior chamber?

Answer 10

0.3 ml

Replaced roughly every hour

Question 11

Where is aqueous humour drained?

Answer 11

Iridocorneal angle (in the sclera) which contains the trabecular meshwork
Meshwork offers resistance to outflow of aqueous humour
Enters canal of Schlemm

Question 12

Where does the aqueous humour go after entering the Canal of Schlemm?

Answer 12

Drains into collector channels
Into aqueous veins
Into the episcleral veins
Into larger ophthalmic veins

Question 13

What is the path of the uveo-scleral pathway?

Answer 13

Passes through ciliaris muscle into choroid
Into suprachoroidal space
Into sclera
Into episcleral venous network

Question 14

What is the function of the uveo-scleral pathway?

Answer 14

An accessory pathway
Drains 10-15% of aqueous humour
Used when there is pathology blocking main pathway eg haemorrhage, infection –> debris leading to increased resistance in trabecular meshwork

Question 15

Where do phagocytic cells reside?

Answer 15

1. On surface of plates that make up trabecular meshwork
2. Interstitial jelly surrounding canal of schlemm
3. Epithelial posterior surface of iris
   KEEPS HUMOUR CLEAR

Question 16

Where is the iridocorneal angle?

Answer 16

Anterior to iris

Question 17

What is the main consequence of increased IOP?

Answer 17

1. Mechanical pressure on ganglion cells of retina and nerve axons leads to degeneration
2. Mechanical pressure on central retinal artery and its branches leads to ischaemia
   - -> Optic nerve becomes smaller and optic cup becomes pathologically deep