BS - Anterior Chamber - Week 3

Question 1

What is the normal intraocular pressure?

Answer 1

10-20 mmHg.

Question 2

Define the anterior chamber angle. From what structure on the anterior surface of the eye can it be reached?

Answer 2

The junction between the iris and cornea.

Can be reached from the limbus, directly deep.

Question 3

What is the scleral sulcus, and what is its anterior border?

What bridges the sulcus?

Answer 3

The sulcus is the inside surface of the limbal depression. The anterior border is the canal of Schlemm.
The trabecular meshwork bridges the scleral sulcus.

Question 4

What is the scleral spur? What is its purpose?

Answer 4

The posterior border of the scelral sulcus. Prevents the canal of Schlemm from collapsing under cilliary muscle contraction.

Question 5

What is Schwalbe’s line? Is it precisely defined? What transition happens here?

Answer 5

The point on the cornea where Descemet’s membrane ends.

Is a smooth transition, and not a defined sharp line. Transition from endothelium to trabecular meshwork occurs.

Question 6

What forms the trabecular meshwork?

Answer 6

Connective tissue beams enclosed by trabecular cells.

Question 7

What are the inner layers of the trabecular meshwork like?

Answer 7

Plate-like cribriform

Question 8

What does the outer layers of the trabecular meshwork form?

Answer 8

Lamellated meshwork

Question 9

Which areas of the trabecular meshwork drain/dont drain?

Answer 9

The anterior border of the meshwork is non-draining.

The posterior trabecular meshwork is where the bulk of draining occurs.

Question 10

Name and describe the two zones of the lamellated meshwork.

Answer 10

Uveal - ropelike, large irregular openings

Corneoscleral - sheets perforated by elliptical openings

Question 11

Describe the deepest layer of the trabecular meshwork. What kind of network does it contain, and what is it continuous with?

Answer 11

Juxtacanalicular (cribriform) - sieve-like plates
High resistance
Has a network of elastic fibres, continuous with the ciliary muscle tendons.

Question 12

Where do ciliary muscles insert, and what is a consequence of ciliary muscle contraction?

Answer 12

They insert into the juxtacanalicular/cribriform plexus.

Contraction results in the widening of their intercellular spaces.

Question 13

What do cells of the trabecullar meshwork produce, and how is the meshwork cleaned of debris?

Answer 13

They produce GAGs, glycoproteins, and fibrils.

Are highly phagocytic, removing debris from the meshwork.

Question 14

What lines the canal of Schlemm?

Answer 14

Endothelial cells.

Question 15

How does the bulk of the aqueous humour reach the canal of Schlemm?

Answer 15

The formation of giant vacuoles within the endothelial cells.

Question 16

Describe the 5 steps of trabecular outflow.

Answer 16

• Through the trabecular meshwork
• Through Schlemm’s canal
• Through external collector channels of Maggiore
• Through the deep intrascleral venous plexus
• To the episcleral veins and vortex system

Question 17

Aqueous humour flows from the anterior chamber to the episcleral veins. What is the pressure within these structures?

Answer 17

Episcleral veins - 9 mmHg

Intraocular pressure - 10-20 mmHg

Question 18

Aside from the trabecular pathway of drainage, describe the second pathway, and the percentage of outflow it accounts for vs the trabecular pathway.

Answer 18

Uveoscleral pathway
Between uveal trabeculae and ciliary muscle bundles, aqueous humour is absorbed by blood vessels here, and drain to the episclera.
Accounts for 10-15% of aqueous humour drainage.
Trabecular pathway forms 80-85%.

Question 19

Describe the effect of ciliary muscle contraction on the two aqueous drainage pathways.

Answer 19

Trabecular - opens trabecular pores, increasing drainage

Uveoscleral - Reduces space between ciliary muscle fibres, reducing drainage

Question 20

What is a pupillary block, and when is it performed?

Answer 20

A laser is used to burn a hole in the iris, used when aqueous drainage is blocked.

Question 21

What 5 anatomical abnormalities would predisposition an individual to obstructed aqueous outflow?

Answer 21

• Narrow anterior chamber angle
• Shallow anterior chamber depth
• Thicker lens
• Lens positioned more anteriorly
• Small corneal diameter/shorter axial length

Question 22

What happens to the trabecular meshwork with age?

Answer 22

Accumulates with collagen, resulting in smaller pores, and decreased outflow.

Question 23

Describe gonioscopy.

Answer 23

Using a 3-4 mirrored instrument to look at the anterior chamber angle.

Question 24

During gonioscopy, describe the structures seen, going from superior to inferior.

Answer 24

Cornea
Anterior chamber
Schwalbe's line
Trabecular meshwork
Scleral spur
Ciliary bodies
Iris
Pupil

Question 25

Define glaucoma.

Answer 25

Increased intraocular pressure.