Exam 1 Koh- Aqueous Humor 2

Question 1

What are the 3 outflow systems of the AH?

Answer 1

Corneoscleral meshwork, uveoscleral meshwork and episcleral vessels

Question 2

What is the conventional outflow of the AH?

Answer 2

(65-90%) trabecular meshwork, Schlemm canal, collector vessels, intrascleral plexus, episcleral venous system

Question 3

What is the uveoscleral outflow of the AH?

Answer 3

(Pressure insensitive) Pass across the face of ciliary muscle, into suprachoroid, and through scleral coat to end in the vortex system

Question 4

What is the trabecular meshwork?

Answer 4

A specialized tissue at the chamber angle, is the major site for regulation of the normal bulk flow of the aqueous humor; superficial uveal meshwork, the deeper corneoscleral meshwork, and the juxtacanalicular connective tissue (JCT) adjacent to Schlemm’s canal

Question 5

How does the trabecular meshwork function?

Answer 5

Self-cleaning, unidirectional, pressure-sensitive, low- flow (2 micoliters/min/mmHg) biologic filter for the AH, and contributes thereby to control of the IOP

Question 6

What is the trabecular meshwork outflow pathway?

Answer 6

Trabecular meshwork, Schlemm’s canal, and the collector channels/aqueous veins

Question 7

What is Schlemm’s canal?

Answer 7

The inner wall endothelium, its basement membrane and the canal lumen

Question 8

What are collector channels?

Answer 8

Collector channels and aqueous veins connect the canal lumen to the episcleral veins on the surface of the eye

Question 9

How many collector channels are along the outerwall of Schlemm’s canal?

Answer 9

30

Question 10

What is the trabecular meshwork structure?

Answer 10

A lattice of connective tissue and endothelial cells embedded in GAG-like ground substance, then into the Schlemm canal and general venous circulation (episcleral vessels)

Question 11

Why is there resistance in the trabecular meshwork?

Answer 11

In the vicinity of the inner wall endothelium of Schlemm’s canal, its basement membrane, and the juxtacanalicular connective tissue

Question 12

What are the tissue beams in the trabecular meshwork?

Answer 12

Or lamellae that have a core of collagenous and elastic fibers, and care covered by flat cells which rest on a basal lamina. The beams attach to one another in several layers and form a porous filter-like structure

Question 13

What are the properties of the trabecular meshwork cells?

Answer 13

Have active phagocytic properties, high levels of cytoskeletal actin, lower levels of microtubules also contain vimetin and desmin = smooth muscle

Question 14

Trabecular meshwork cells are specialized both for ______ transport of water and solutes and ______

Answer 14

Endocytic, contractility

Question 15

Most of the matrix component in trabecular meshwork are synthesized and degraded by _______ cells

Answer 15

Endothelial

Question 16

The phagocytic activity of TM cells is associated with what two things?

Answer 16

GAG-degrading enzymes and acid phosphatase

Question 17

Each lamella or beam mostly contains what types of collagen?

Answer 17

1 and 3

Question 18

The fine fibril contain what type of collagen?

Answer 18

6

Question 19

The cells covering the trabecular meshwork beams is rich in collagen type ____ and ___

Answer 19

4 and laminin

Question 20

The elastic fibers in collagen have a considerable amount of ____ ____ material

Answer 20

Electron dense

Question 21

The spaces between the juxtaglomerular cells and extracellular maxtrix fibers contains what?

Answer 21

Ground substance, consisting of various proteoglycans and hyaluronan

Question 22

What types of glycosaminoglycans (GAGs) are in the AH?

Answer 22

Hyaluronic acid, dermatan sulfate, and chondroitin sulfate

Question 23

What are plaques?

Answer 23

Accumulation of extracellular matrix structures with age

Question 24

What contributes to interstitial flow resistance?

Answer 24

Proteoglycans and GAGs

Question 25

AH outflow resistance may be decreased by nearly 50% in bovine eyes after perfusion with _________

Answer 25

Hyaluronidase

Question 26

Secreted ECM proteins influence cell function by modulating ______ ______

Answer 26

Cell-matrix interactions

Question 27

What are the matrix proteins?

Answer 27

Elastin, fibronectin, versican, laminin, thrombospondin-1, SPARC (secreted protein, acidic and rich in cysteine), myocilin, optineurin

Question 28

What 2 things are active in handling H2O2 and free radicals?

Answer 28

Catalase and a glutathione-dependent system

Question 29

What is TGFb?

Answer 29

A member of a family of dimeric polypeptide growth factors

Question 30

What are the isomers of IGF-b?

Answer 30

TGF-b1, TGF-b2, TGF-b3

Question 31

What is the predominant isoform of TGFb as it is found at relatively high concentration in the AH of normal eyes?

Answer 31

TGF-b2

Question 32

What are the effects of TGF-b?

Answer 32

Signaling does not only effect ECM turnover in the TM, but also acts on the TM actin cytoskeleton

Question 33

The uveoscleral pathway accounts for what percentage of outflow?

Answer 33

10-35%

Question 34

What is the resistance like in the uveoscleral outflow?

Answer 34

Minimal, main resistance is within the ciliary muscle

Question 35

Which outflow has prostaglandin F2alpha analongs?

Answer 35

Uveoscleral

Question 36

What is the uveoscleral flow rate?

Answer 36

Pev to be about 8mmHg, calculated uveoscleral outflow to be about 0.8 micoliters/min (36%)

Question 37

What are the values for uveoscleral flow?

Answer 37

In normal eyes between 0.14 and 1.52 micoliters/min, constituting 12-54% of total aqueous outflow

Question 38

Which outflow is more sensitive to pressure change?

Answer 38

Trabecular outflow

Question 39

What is episcleral venous pressure?

Answer 39

Aqueous humor draining via the canal of Schlemm into a network of intrascleral collector channels that drain into the scleral veins

Question 40

Uveoscleral drainage is possible owing to the fact that pressure in suprachoroid is _____ mmHg lower than in the anterior chamber

Answer 40

2-4

Question 41

The difference from the suprachoroid and the anterior chamber can be reversed after _______ and can lead to hypotony and choroidal effusions

Answer 41

Trabeculectomy

Question 42

What are glaucoma risk factors?

Answer 42

IOP, CCT, age, C/D ratio, VF loss, pseudoexfoliation

Question 43

What is the glaucoma continuum?

Answer 43

Normal -> acceleration of apoptosis -> ganglion cell death/axon loss -> Retinal nerve fiber layer change (undetectable) -> Retinal nerve fiber layer change (detectable) -> short wavelength automated perimetry VF changes -> standard automated perimetry VF changes -> VF change (moderate) -> VF change (severe) -> blindness

Question 44

What are features of primary open angle glaucoma?

Answer 44

Excessive depletion of meshwork cells, failure of phagocytosis, closure of Schlemm canal, progressive narrowing of the lumina of collector channels

Question 45

What happens to the trabecular meshwork in primary open angle glaucoma?

Answer 45

Thickening and fusion of trabeculae, alterations in meshwork myocillin, accumulation of ECMs, GAGs, glycoproteins and small proteins in the JCT

Question 46

What are 3 glucocorticoids used in the AH?

Answer 46

Dexamethasone, actin, and MMPs

Question 47

What does dexamethasone do?

Answer 47

Increased deposition of extracellular matrix material in the outflow pathway, increased expression of myocilin

Question 48

What does actin do?

Answer 48

Cause the formation of cross-linked actin networks in cultured HTM cells, less pliable and more likely to inhibit outflow

Question 49

What do MMPs do?

Answer 49

Downregualtes matrix-metalloproteases (MMP2,3, and 14), less ECM turnover and less outflow, MMP3 to help degrade and remodel ECM

Question 50

What are glucocorticoid effects on the trabecular meshwork?

Answer 50

TM cells have GC receptors and targets of GC activtiy, GCs alter the expression of hundreds of TM cells, genes, and proteins; GCs alter TM cell functions (decrease proliferation and phagocytosis), GCs increase extracellular matrix deposition, GC reorganize the actin cytoskeleton, GCs alter cellular junctions

Question 51

What are the autonomic regulation steps for secretion of AH?

Answer 51

Ciliary body to posterior chamber: 1) uptake of solute and water at stromal surface by PE, 2) transfer from PE to NPE cells through gap junctions 3) transfer of solute and water by NPE cells into PC

Question 52

Adrenergic receptors regulate IOP via ____ ____

Answer 52

Adenylate cyclase

Question 53

What suppresses aqueous flow?

Answer 53

Beta blocker and alpha adrenergic agonists

Question 54

Muscarinic receptors are linked to what?

Answer 54

PIP2 2nd messenger system (CB)

Question 55

What 2 medications have good nocturnal efficacy?

Answer 55

Carbonic anhydrase inhibitor, prostaglandins (good but less than daytime)

Question 56

What 2 medications cause a decrease in episcleral venous pressure?

Answer 56

Alpha-2- agonists and prostaglandins

Question 57

What 3 medications increase uveoscleral outflow?

Answer 57

Adrenergic agents, alpha-2-agonists, prostaglandins

Question 58

What medication decreases uveoscleral outflow?

Answer 58

Miotics

Question 59

What 2 medications increase conventional out flow facility?

Answer 59

Miotics and prostaglandins

Question 60

What 3 medications decrease aqueous humor flow?

Answer 60

alpha-2-agonists, beta-adreno-ceptor antagonists, carbonic anhydrase inhibitors

Question 61

What 2 medications cause a slight increase in aqueous humor flow?

Answer 61

Miotics and adrenergic agents