ANTERIOR CHAMBER ANGLE

Question 1

Which 2 of the following structures create the peripheral boundary of the anterior chamber?

Answer 1

Trabecular meshwork, ciliary body

Question 2

Which of the following statements best describes the convection current of the aqueous humor in the anterior chamber?

Answer 2

Aqueous flows up posteriorly near the iris and down anteriorly near the cornea

Question 3

Which of the following structures lies directly internal to the Schlemm’s canal?

Answer 3

Juxtacanalicular meshwork

Question 4

Which of the following best describes the anterior chamber structures seen with gonioscopy from posterior to anterior?

Answer 4

Ciliary body - scleral spur - trabecular meshwork - Schwalbe’s line

Question 5

If the most posterior structure seen on gonioscopy is the trabecular meshwork, which 2 of the following structures are NOT visible?

Answer 5

Scleral spur, Ciliary body

Question 6

Which 2 of the following characteristics is consistent with the conventional outflow pathway of aqueous humor?

Answer 6

Involves Schlemm’s canal, pressure dependent

Question 7

Giant vacuoles that play a role in aqueous humor outflow are found at which of the following locations?

Answer 7

Inner wall of Schlemm’s canal

Question 8

Which of the following paths best describes the pathway used by the aqueous veins?

Answer 8

Schlemm’s canal - aqueous veins - episcleral veins - anterior ciliary veins

Question 9

The longitudinal fibers of the ciliary body are connected to which 4 of the following structures?

Answer 9

Scleral spur, corneoscleral meshwork, juxtacanalicular meshwork, uveal meshwork

Question 10

Which of the following statements best describes the impact of ciliary body contraction on aqueous outflow?

Answer 10

Uveoscleral outflow will decrease; conventional outflow will increase

Question 11

If the most posterior structure seen is anterior trabecular meshwork, which angle structures are NOT visible?

Answer 11

Scleral spur, ciliary body, posterior trabecular meshwork

visible = TM, SL

Question 12

Which of the following internal to external structure sequences best represents the anterior chamber structures at the tip of the arrow?

Answer 12

Uveal meshwork - ciliary body - sclera

Question 13

A traumatic detachment of the ciliary body from the sclera spur is termed:

Answer 13

Cyclodialysis

Question 14

What is the conventional outflow pattern for aqueous humor?

Answer 14

The bulk of the aqueous humor (80-90%) then leaves the anterior chamber via the trabecular meshwork & Schlemm’s canal (a continuous narrow channel that completely encircles (360°) the anterior chamber angle). Aqueous humor exits Schlemm’s canal, travels via a series of venous plexuses in the sclera and ultimately drains to the episcleral venous plexuses.

Question 15

What are all the structures seen in the anterior chamber angle from posterior to anterior if the angle is wide open?

Answer 15

Structures in the anterior chamber angle starting posteriorly & moving anteriorly are:
> Ciliary Body muscle (its anterior surface)
> Scleral Spur
> Trabecular meshwork
> Schwalbe’s line or ring (peripheral termination of
Descemet’s membrane)

Question 16

What is Schwalbe’s line?

Answer 16

Schwalbe’s line is the anterior limit of the anterior chamber angle. It may blend with the corneal dome and not be distinguishable, appear as a light band above the TM, or pigmented to a variable degree especially in the inferior angle (since pigment accumulates in inferior angle due to gravity).

Schwalbe’s line/ring represents termination of Descemet’s membrane peripherally at limbus.

Question 17

What attaches to the sclera spur anterior? Posteriorly?

Answer 17

The scleral spur is a small ridge of sclera that projects into the anterior chamber. All the fibers of the ciliary body muscle insert into the posterior surface of the scleral spur. The trabecular meshwork inserts into the anterior surface of the scleral spur.

Question 18

What does the ciliary body muscle attach to anteriorly? Be specific and complete.

Answer 18

The longitudinal fibers (meridional), which are the most external, attach the ciliary body anteriorly to the scleral spur and trabecular meshwork at the limbus, and posteriorly to the suprachoroidal lamina (fibers connecting choroid and sclera) as far back as the equator of the eye.

Question 19

Why do trabecular endothelial cells decrease in number as we get older? There are 2 answers to this

Answer 19

1. it is widely held that after a certain amount of phagocytosis the trabecular cells round up, leave the beams and migrate out of the eye, leading to a decrease in the number of trabecular cells with increased age
2. The trabecular endothelial cells of the meshwork also have limited mitotic activity to replace lost trabecular cells. This could also explain the decrease in number of trabecular endothelial cells seen with increased age.

Question 20

What are 2 possible vessels that the aqueous veins arise from?

Answer 20

1. **Aqueous veins may arise directly from outer wall of Schlemm’s canal: Schlemm’s canal ® aqueous veins ® episcleral veins ® anterior ciliary veins ®
   muscular veins ® superior or inferior ophthalmic veins

OR

2. **Aqueous veins may arise from the deep scleral venous plexus:
   Schlemm’s canal ® external collector channels ® deep scleral venous plexus ®
   aqueous veins ® episcleral veins ® anterior ciliary veins ® muscular veins ® superior or inferior ophthalmic veins

Question 21

Blood in the deep sclera plexus will directly interconnect these 2 venous structures:

Answer 21

External collector channels and the intrascleral venous plexus

Question 22

Describe the path of uveoscleral outflow starting at the anterior chamber and ending at lymphatic vessels of the conjunctiva.

Do prostaglandins increase or decrease uveoscleral outflow? What is their mechanism of action?

Answer 22

From the suprachoroidal space the aqueous humor can either:
1. pass through the sclera itself (uveoscleral outflow) to the lymphatic vessels of the conjunctiva (or orbit lymphatics) or beyond to eventually reach the systemic circulation.
2. pass through the scleral emissarial channels for the vortex veins (uveovortex outflow) to the lymphatic vessels of the conjunctiva (or orbit lymphatics) or beyond to eventually reach the systemic circulation.
(It takes 2 hours or more for aqueous humor to travel from the anterior chamber to the general circulation via this route).

Prostaglandin analogs can reduce intraocular pressure 25-30% by increasing uveoscleral outflow (e.g. latanoprost = Xalatan) by remodeling the extracellular matrix in the CB muscle. Acts on CB muscle prostanoid receptors to increase synthesis of matrix metalloproteinases and dissolve CT matrix between smooth muscle fibers. Collagen content is altered, as the metalloproteinases dissolve collagen types 1 and 3.
> The result is widening of CT spaces between longitudinal fibers and increased uveoscleral outflow

Question 23

What is cyclodialysis?

Answer 23

Trauma to one eye, could lead to the ciliary body muscle being torn away from its scleral spur attachment, termed cyclodialysis.

With cyclodialysis the longitudinal muscle of the ciliary body is detached from its normal scleral spur attachment site. It usually in a small area but it can also occur over a larger area.

It effectively creates open communication between the anterior chamber and the supraciliary space (which then leads into the suprachoroidal space). This results in markedly enhanced uveoscleral outflow causing decreased intraocular pressure (ocular hypotony)

Question 24

If the anterior trabecular meshwork is the most posterior structure visible with gonioscopy, what angle structures are NOT seen?

Answer 24

Ciliary body and scleral spur

Question 25

How does CB muscle contraction affect aqueous outflow out the TM and what is the mechanism of action?
How does it affect uveoscleral outflow and what is the mechanism of action?

Answer 25

CB muscle contracting leads to a mechanical opening of the trabecular meshwork spaces (via pulling on the scleral spur and trabecular meshwork) and resist collapse of Schlemm’s canal (via the cribriform plexus’ elastin-containing fibrils) leading to increased aqueous humor outflow via the corneoscleral pathway.

However, contraction of CB muscle compresses the intercellular channels between the ciliary body muscle fibers, thus DECREASING aqueous humor outflow via this route.

Question 26

How are the anterior and posterior parts of the TM different?

Answer 26

Trabecular meshwork is a triangular wedge of tissue that encircles the outer circumference of the anterior chamber 360° and lies directly internal to Schlemm’s canal.
□ The apex of this triangle is attached to Schwalbe’s line. Expanding from this apex posteriorly, the trabecular meshwork attaches to the scleral spur & the stromas of
the ciliary body and the peripheral iris.
□ Projecting into the base of this triangle is the shelf-like lip of sclera termed the scleral spur.

> UVEAL MESHWORK is the portion of the trabecular meshwork that lies closer to the anterior chamber (innermost). It extends from Schwalbe’s line to the stroma of the ciliary body & iris (which are “uveal” tract structures and hence it name “uveal” meshwork) where it attaches to the longitudinal ciliary body muscle fibers. It does NOT attach to the scleral spur; rather IT LIES INTERNAL TO THE SCLERAL SPUR.

> CORNEO-SCLERAL MESHWORK (middle)
is the part of the trabecular meshwork lying just external to the uveal meshwork. It likewise extends from Schwalbe’s line anteriorly, but posteriorly it connects to the anterior surface of the scleral spur (so it essentially runs from cornea (Schwalbe’s line ) to the scleral spur; hence its name “corneoscleral” meshwork).

> JUXTA-CANALICULAR MESHWORK (outermost) is the part that lies directly adjacent to Schlemm’s canal.

Question 27

Name the layers of a trabecular beam starting closest to the lumen of the meshwork. Which of the 3 parts of the meshwork have trabecular beams?
Which part of the trabecular meshwork has the smallest openings (spaces of Fontana)? Which part of the TM lies closest to the anterior chamber?

Answer 27

Trabecular beams of the uveal & corneoscleral meshwork consists of an inner core of collagen & elastic fibers covered by single layer of endothelial cells (called “trabecular cells”) that rest on a basement membrane.

The cribriform layer, the corneoscleral meshwork, and the uveal meshwork have trabecular beams.

The uveal and corneoscleral meshwork have a similar structure, being composed of sponge-like, connective tissue beams with intervening spaces (called the “spaces of Fontana”) that are arranged as superimposed perforated sheets. The spaces become progressively smaller from its inner part (by the anterior chamber) to its outer part (by Schlemm’s canal).

Question 28

While doing gonioscopy, you push too hard and see blood in Schlemm’s canal. What part of the angle are you seeing this blood through? Why?

Answer 28

If the episcleral venous pressure is elevated above the intraocular pressure, as in pressing down on the cornea with a gonioscopy lens (compressing the episcleral veins), Schlemm’s canal will be back-filled with blood.

This technique of applying pressure to the eye with the gonioscopy lens is sometimes used clinically to identify the location of the trabecular meshwork if its location is in doubt.

Since Schlemm’s canal lies directly external to the trabecular meshwork, blood in Schlemm’s canal will be seen through the meshwork as a thin red line if blood is
backed up in Schlemm’s canal.

Question 29

What is angle recession? Be specific. How does it appear with gonioscopy?

Answer 29

If there is a history of trauma to one eye, the ciliary body band may appear much thicker compared to the normal eye and the clinical term for this is “angle recession”.

In angle recession, there is a tear of the anterior face of the ciliary body muscle usually between the longitudinal and circular muscle fibers of the CB.

While the insertion of the longitudinal CB muscle fibers to the scleral spur remains intact, the circular fibers are displaced posteriorly along with the iris root & pars plicata. As a result, more longitudinal CB muscle is exposed when viewed with gonioscopy so the ciliary body band may appear much thicker compared to the normal eye.

Question 30

What types of junctions join adjacent trabecular endothelial cells? What types of junctions join adjacent endothelial cells of the inner wall of Schlemm’s canal? What types of junctions join adjacent endothelial cells of the outer wall of Schlemm’s canal?

Answer 30

ADJACENT TRABECULAR ENDOTHELIAL CELLS
Trabecular endothlelial cells are directly continuous with the corneal endothelial cells, but are larger and more irregular in shape than the corneal endothelial cells.
> The trabecular endothelial cells are joined by:
- gap junctions & desmosomes
- short, discontinuous tight junctions (but NO ZONULA OCCLUDENS JUNCTIONS) so aqueous humor can readily permeate the core of the trabecular
beams

ADJACENT ENDOTHELIAL CELLS OF INNER WALL OF SCHLEMM’S CANAL
Schlemm’s canal is lined by an endothelium. The endothelial cells lining the inner wall are continuous non-fenestrated endothelial cells interconnected by zonula occludens junctions of variable complexity.

ADJACENT ENDOTHELIAL CELLS OF OUTER WALL SCHLEMM’S CANAL
The endothelial cells on the outer wall are longer & flatter. These endothelial cells are joined by zonula
occludens junctions but DO NOT form vacuoles.

Question 31

What 3 cell types are found in the area of the TM and which are phagocytic?

Answer 31

Collagen + elastic fibers
Endothelial cells
Basement membrane

The trabecular endothelial cells are phagocytic while on the beams, so they play a role in keeping the trabecular spaces free of potential obstructive debris like blood, pigment, etc.

Question 32

If you note an aqueous vein on a patient during slit lamp exam, what was unique about it that you could recognize it definitely as an aqueous vein? Explain how this feature occurs.

Answer 32

Aqueous veins are channels that take a less tortuous route (bypassing the scleral plexuses) & drain directly into the episcleral veins. These aqueous veins are clear since they normally contain only clear aqueous humor, not blood (hence their name).

The aqueous veins are clinically identifiable near the limbus at 3 o’clock & 9 o’clock position because the aqueous & blood has not yet mixed by the time they reach the episcleral veins, so a clear stream of aqueous humor is noted in the center of the vessel lumen while slower moving blood borders it on either side (i.e. “laminar flow” of aqueous humor and blood). Further downstream, the aqueous humor does mix with the blood.

Question 33

(CO) 1. Describe the boundaries of the anterior chamber

Answer 33

The boundaries of the anterior chamber are:

• anterior: posterior surface of the cornea
• posterior: anterior surface of the iris & anterior surface of lens (that lies in the pupillary aperture
• peripheral: trabecular meshwork and anterior surface of ciliary body

Question 34

(CO) 2. State the difference in depth of the anterior chamber for hyperopes vs. myopes and how the
depth changes with advanced age as the lens has gotten bigger.

Answer 34

The anterior chamber is shallower in hyperopes and deeper in myopes, but it is usually equal in size between the two eyes of an individual.
As lens gets bigger, the anterior chamber will become narrower for both.

Question 35

(CO) 3. Name and describe the structures in the anterior chamber angle starting posteriorly and
ending anteriorly.

Answer 35

see previous question

Question 36

(CO) 4. Name the structures that insert into the scleral spur anteriorly and posteriorly

Answer 36

The scleral spur is a small ridge of sclera that projects into the anterior chamber. All the fibers of the ciliary body muscle insert into the posterior surface of the scleral spur. The trabecular meshwork inserts into the anterior surface of the scleral spur.

Question 37

(CO) 5. Name the three regions of the trabecular meshwork. Be sure to know:

• which region lies closest to Schlemm’s canal
• which region lies closest to the anterior chamber and is visible with gonioscopy.

Answer 37

see previous question *uveal (closest to anterior chamber, visible with gonio)

Question 38

(CO) 6. Describe the anatomy/histology of the three regions of the trabecular meshwork, including
similarities and differences.
- Be able to describe the attachments of the three regions of the trabecular meshwork.

Answer 38

UVEAL MESHWORK -> closest to anterior chamber; made of a series of slender endothelial cell lined beams (trabeculae=beams) or cords separated by large spaces (25-75 μm wide), so it has a Swiss cheese- like appearance.

• anterior to scleral spur
• posteriorly blends with stroma of CB/iris and anteriorly extends to Schwalbe’s line
• attaches to the longitudinal fibers of the CB muscle posteriorly & Schwalbe’s line anteriorly

CORNEOSCLERAL MESHWORK

• broader, flatter endothelial cell-lined beams with fewer/smaller openings more elliptical (Havarti cheese)
• adjacent sheets are not aligned (convoluted path)
• posteriorly, attaches to scleral spur

JUXTACANALICULAR MESHWORK

• adjacent to inner wall of Schlemm’s canal; “cribiform” meshwork
• a cell-rich connective tissue zone with no permanent spaces
• open connective tissue matrix of collagen, glycoprotein, GAGs, elastin, >fibroblast-like cells

Question 39

(CO) 7. Describe the differences between the anterior and posterior TM in terms of pigment
amounts, amounts of aqueous outflow and relationship to Schlemm’s canal.

Answer 39

The trabecular meshwork (TM) is often seen as two stripes: a minimally pigmented anterior meshwork and a more heavily pigmented posterior meshwork.

The posterior portion of the TM is called the “filtering” meshwork because it lies directly internal to Schlemm’s canal and is a dark band (located above the white scleral spur when viewed with the gonioscopy lens; or reddish if there is blood in Schlemm’s canal). Aqueous outflow is greater here and thus the amount of pigment phagocytized by the trabecular endothelial cells in this area is greater.

The anterior portion of the TM has NO Schlemm’s canal external to it and is therefore called the “non-filtering” meshwork
-Very little aqueous outflow occur here so the amount of pigment phagocytized by the trabecular endothelial cells here is also relatively small. Therefore this anterior part of the TM is lighter in color and appears as a lighter band above the darker posterior portion of the meshwork.

Question 40

(CO) 8. Describe a trabecula of the uveal or corneoscleral meshwork (all the layers and their proper
location internal to external)

Answer 40

The trabecular cords have a central core of collagen fibers with a few elastic fibers as well. The collagen core is wrapped by a sheath of trabecular endothelial cells and their basement membrane.

Question 41

(CO) 9. Discuss the trabecular endothelial cells lining the trabeculae of the uveal & corneoscleral

meshwork. Be sure to include:
- what cells the trabecular endothelial cells are directly continuous with anteriorly
- their functions
- mitotic activity
- changes in endothelial cell counts with age and why it occurs.
- junctions that join adjacent trabecular endothelial cells

Answer 41

Trabecular endothelial cells are directly continuous with the corneal endothelial cells, but are larger & more irregular in shape than the corneal endothelial cells.

The trabecular endothelial cells contain:

• organelles for protein synthesis and so they are able to replace the connective tissue components of the trabeculae
• Iysosomes so they are capable of phagocytosis (they remove debris & particulate matter from the aqueous humor and thus facilitate aqueous outflow)

see previous question

Question 42

(CO) 10. Describe the attachments of the ciliary body muscle to the trabecular meshwork, scleral spur and Schlemm’s canal ‘s inner wall (including the tendons) and how they affect aqueous outflow

Answer 42

see previous question

Question 43

(CO) 11. Discuss the role of the ciliary body muscle in aqueous outflow. Also explain how aqueous humor outflow is facilitated by the movement of the CB.

Answer 43

One anterior tendon of the longitudinal CB muscle fibers attaches to scleral spur
- Recall that the corneoscleral meshwork attaches to the scleral spur.
- Therefore contraction of the ciliary body muscle pulls on the scleral spur (which
is displaced posteriorly & internally), which then pulls on the corneoscleral TM and spreads the sheets open (i.e. the spaces between the trabecular beams are enlarged) to increase aqueous humor outflow

Another tendon from the longitudinal CB muscle extends into the outermost corneoscleral trabeculae & also inserts on elastic fibers of the juxtacanalicular meshwork
- contraction of these fibers pulls on the juxtacanalicular TM & spreads the sheets open to increase aqueous humor outflow through the corneoscleral and juxtacanalicular meshwork

Additionally, from these CB tendons, “elastin-containing fibrils” (referred to as the cribriform plexus) spread out within the meshwork & make anatomical connections with the basal lamina of the endothelial cells lining the inner wall of Schlemm’s canal.

• contraction of these fibrils would both pull on the trabecular meshwork to enlarge the spaces and would pull on the endothelial cells of Schlemm’s canal to help prevent (or resist) the collapse of Schlemm’s canal
  (i. e. collapse of Schlemm’s canal would increase outflow resistance) leading to increased aqueous humor outflow.

So, in summary, stimulation of the ciliary body muscle, whether neurologically (parasympathetic fibers) as during accommodation or pharmacologically, in turn causes both a mechanical opening of the trabecular meshwork and resists collapse of Schlemm’s canal, leading to increased aqueous humor outflow.

Question 44

(CO) 12. Describe Schlemm’s canal. Be sure to include its location, anatomical relationships to
the trabecular meshwork, function, endothelial lining of its inner wall, contents of the canal (Blood? Aqueous humor?), type of junction in the endothelial lining.

Answer 44

Schlemm’s canal is a continuous narrow channel that completely encircles (360°) the anterior chamber angle
- It lies external to the juxtacanalicular meshwork
- It conducts aqueous humor from the trabecular meshwork to the venous
circulation

The endothelial cells lining the inner wall are continuous non-fenestrated endothelial cells interconnected by zonula occludens junctions of variable complexity

Although the lumen of Schlemm’s canal is in direct continuity with the venous circulation of the eye, it does not usually contain blood unless intraocular pressure falls below episcleral venous pressure

Question 45

(CO) 13. Describe the process whereby aqueous gets from the meshwork into the lumen of Schlemm’s canal via giant vacuole formation.
- Include where the greatest resistance to outflow is presumed to be located in the trabecular meshwork. Are the cause and/or location confirmed?

Answer 45

The most prominent feature of the inner wall’s endothelium is the presence of giant vacuoles, which are thought to play role in aqueous humor outflow from the trabecular meshwork to Schlemm’s canal.

1. Giant vacuoles are formed as invaginations of the basal portion of the inner wall’s endothelial cell membrane
2. Progressive enlargement of a vacuole leads to formation of a transient trans-cellular channel (see #5 on diagram)
3. After a time the basal infolding is occluded and the cell returns to a non-vacuolated state

Giant vacuole formation is pressure dependent (as lOP increases, the size of the vacuoles increase; as lOP decreases, the size of the vacuoles decrease) but energy independent

**Most of the resistance to aqueous outflow is said to reside in this juxtacanalicular meshwork, however how this resistance is created and its anatomical location remains uncertain.

Question 46

(CO) 14. Describe the flow of aqueous from Schlemm’s canal to the episcleral venous plexus and
anterior ciliary veins. Be sure to include all the possible routes out of Schlemm’s canal and its collector channels.
- Be able to name all the structures involved and where they drain, in the proper order
- Be sure to include how much of the aqueous outflow it accounts for compared to the
uveoscleral outflow path

Answer 46

The bulk of the aqueous humor (80 90%) then leaves the anterior chamber via the trabecular meshwork & Schlemm’s canal (a continuous narrow channel that completely encircles (360°) the anterior chamber angle). Aqueous humor exits Schlemm’s canal, travels via a series of venous plexuses in the sclera and ultimately drains to the episcleral venous plexuses.
> This is the conventional outflow pathway for aqueous humor

Schlemm’s canal -> external collector channels -> deep scleral venous plexus -> intrascleral venous plexus -> episcleral veins -> anterior ciliary veins -> muscular veins -> superior or inferior ophthalmic veins
Note: beyond Schlemm’s canal, blood & aqueous humor are mixed in the lumen of the blood vessels

Question 47

(CO) 15. Describe the uveoscleral outflow route for aqueous drainage from anterior chamber to
anterior ciliary veins.
- Be sure to include how much of outflow it accounts for compared to the outflow path
through Schlemm’s canal.
- Include the effects of ciliary body muscle contraction on uveoscleral outflow.

Answer 47

Uveoscleral outflow (also referred to as uveovortex outflow) is an alternate pathway for the outflow of aqueous humor from the anterior chamber and it is pressure independent.

It accounts for 10-20% of the total aqueous humor outflow. Fluids and larger molecules in the anterior chamber can pass into and through the uveal meshwork (that attaches to the CB muscle) and then pass through the spaces between the ciliary muscle fibers via the ciliary body’s “anterior face” (the part of the CB in the anterior chamber angle).

Since this aqueous flow path goes through the intercellular spaces between ciliary body (CB) muscle fibers, contraction of the CB muscle should DECREASE uveoscleral outflow. CB muscle contraction would compress the intercellular spaces between the CB
muscle fibers, effectively decreasing aqueous outflow through the spaces

Question 48

(CO) 16. Describe the mechanism of action of prostaglandin analogs like xalatan in increasing uveoscleral outflow.

Answer 48

Some prostaglandin analogs can reduce intraocular pressure 25-30% by increasing uveoscleral outflow (e.g. latanoprost = Xalatan) by remodeling the extracellular matrix in the CB muscle.

see previous question for mechanism

Question 49

(CO) 17. Discuss and describe the mechanism of action of pilocarpine on aqueous outflow via Schlemm’s canal and uveoscleral outflow.

Answer 49

In the past, pilocarpine was frequently used to lower IOP in glaucoma.
Mechanism of action: pilocarpine stimulates the CB muscle to contract leading to a mechanical opening of the trabecular meshwork spaces (via pulling on the scleral spur and trabecular meshwork) and resist collapse of Schlemm’s canal (via the cribriform plexus’ elastin-containing fibrils) leading to increased aqueous humor outflow.
However, uveoscleral outflow is reduced: Contraction of CB muscle compresses the intercellular channels between the ciliary body muscle fibers, thus DECREASING aqueous humor outflow via this route

Question 50

(CO) 18. Be able to name the structures that would be seen on a gonioscopy view of a wide open anterior chamber angle starting posteriorly and moving anteriorly, or a narrower angle (whether given a diagram to label or not). For example: the TM is the most posterior structure visible with gonioscopy. What other angle structures are seen? Not seen?

Answer 50

see previous question

Question 51

(CO) 19. Be able to state what structure lies directly external to the trabecular meshwork

Answer 51

Since Schlemm’s canal lies directly external to the trabecular meshwork, blood in Schlemm’s canal will be seen through the meshwork as a thin red line if blood is
backed up in Schlemm’s canal.

Question 52

(CO) 20. Define/ describe angle recession and cyclodialysis.

Answer 52

see previous question

Question 53

(CO) 21. Describe Schwalbe’s line including:
What structure it represents / what it is
Define posterior embryotoxon

Answer 53

Schwalbe”s line is the anterior limit of the anterior chamber angle. It represents the termination of Descemet’s membrane peripherally at the limbus.

Posterior embryotoxon = when Schwalbe’s line/ring may be hypertrophied (enlarged or thickened) and displaced anteriorly (in the anterior chamber) as a thick white band.

It is visible through a clear cornea as a sharply defined, concentric white line/ring or opacity anterior to the limbus. Usually it is visible just inside the temporal limbus.