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Ocular Anatomy > Lecture 12 A: Aqueous Humor > Flashcards

Lecture 12 A: Aqueous Humor Flashcards

1
Q
A
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2
Q
A
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3
Q

where is the internal scleral sulcus located?

A

located at internal “corneoscleral junction”

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4
Q

what structures does the internal scleral sulcus house?

A
  • trabecular meshwork (TM)
  • Schlemm’s canal (SC)
  • scleral spur (SS)
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5
Q

what is filtration apparatus

A

aqueous drainage facilitated by structures (TM, SC, SS) housed in the internal scleral sulcus

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6
Q

is Schwalbe’s line the most anterior or posterior structure and what is formed by

A

the anterior-most structure formed by Descemet’s membrane

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7
Q

what structure occupies the inner aspect of the internal scleral sulcus

A

TM

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8
Q

what shape is TM and where is it in regards to apex/base?

A

triangular shape with the apex at Descemet’s membrane (Schwalbe’s line) and base at scleral spur)

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9
Q

does the TM inner face border the anterior or posterior chamber

A

anterior chamber

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10
Q

where does the outer side of the TM face?

A

corneal stroma, sclera, schlemm’s canal

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11
Q

Schlemm’s Canal (SC) is what type of vessel and is outer and anterior to what structures

A

circular vessel, outer to TM and anterior to SS

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12
Q

scleral spur (SS)

A

posterior edge of internal scleral sulcus

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13
Q

what are the angle structures from posterior to anterior

A
  • ciliary body band (CBB)
  • scleral spur (SS)
  • trabecular meshwork (TM)
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14
Q

what forms Schwalbe’s line?

A

Descemet’s membrane terminating at the limbus

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15
Q

open angles

A

if all structures are visible

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16
Q

closed angle

A

if TM and posterior structures are not visible

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17
Q

why is the availability of anterior chamber angle structure clinically important

A

because the angle is the location of exit for aqueous humor (which must be able to freely flow

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18
Q

if the exit of the angle is blocked what will happen to pressure

A

pressure within the eye will increase

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19
Q

how can the width of the angle be estimated/graded

A

using a slit lamp and a Gonio lens to determine whether the angle appears wide enough to provide easy access to the trabecular

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20
Q

Gonioscopy

A
  • is performed during the eye exam to evaluate the internal drainage system of the eye
  • also referred to as the anterior chamber angle
  • The “angle” is where the cornea and the iris meet
  • This is the location where fluid inside the eye (aqueous humor) drains out of the eye and into the venous system.
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21
Q

how many regions does the posterior chamber contain and what are they?

A
  1. Canal of Hannover: area occupied by zonules
  2. Canal of Petit: retrozonular space, the area from most posterior zonule to anterior vitreal face (potential space)
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22
Q

what is the difference between the two aqueous drainage pathways: TM Route and Uveoscleral Route

A
  1. TM (generally 90% of flow but can range from 65-95%)
    • CONVENTIONAL
      • TM – corneoscleral meshwork – juxtacanicular tissue – schelmm’s canal – episcleral veins
  2. Uveoscleral (generally 10% of flow but can range from 5 -35%)
    1. UNCONVENTIONAL
      • fluid exits uveal meshwork – ciliary muscle bundle – SAS – absorbed in sclera or anterior ciliary veins or vortex veins
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23
Q

T/F: TM route is not pressure dependent

A

F: TM route is pressure dependent

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24
Q

is there active transport involved in the TM route

A

yes

25
Q

TM route is based on pressure gradient between what?

A
  • intraocular pressure (IOP) and episcleral venous pressure (EVP)

15 mmHg vs 7 mmg

26
Q

T/F: Uveoscleral route is pressure dependent

A

F: Uveoscleral route is pressure independent

27
Q

in the Uveoscleral route, open face of ciliary body band allows for what?

A

eggression via the space between the ciliary muscle fiber bundles to the supraciliary – SAS – from this point multiple ways out

28
Q

how many regions does the TM have and what are they?

A
29
Q

sustained resistance to outflow usually results in what

A

elevated IOP

30
Q

what is limbal conjunctiva formed by?

A

epithelium and loose connective tissue stroma

31
Q

tenons capsule forms what over what?

A

thin, poorly defined connective tissue over episclera

32
Q

limbal stroma is composed of

A

scleral and corneal tissues that merge

33
Q

conjunctival stromal vessels form what

A

peripheral corneal arcades which extend anteriorly to termination of bowmans layer

34
Q

episcleral vessels are cut in different planes and the vessels form what?

A

intra-scleral and deep scleral are within the limbal stroma

35
Q

sclera spurs have what type of collagen fibers and where are they located

A
  • course/dense collagen fibers
  • anterior part of the longitudinal portion of the ciliary muscle merges with the scleral spur and TM
36
Q

sheets of TM are outer to

A

cords of uveal meshwork

37
Q

where does the iris process arise and what does it join

A

iris surface and join TM a the level of the anterior portion of the scleral spur

38
Q

descemet’s membrane terminates where and what does it outline

A

within the anterior portion of the triangle outline aqueous outflow system

39
Q

Trabecular Route flow

A
  1. TM
  2. corneoscleral meshwork
  3. juxtacanalicular meshwork (JCT)
  4. schlemm’s canal (SC)
  5. collector channel (CC)
  6. deep scleral plexus (e)
  7. intrascleral plexus (d)
  8. episcleral veins (c)
40
Q

in the uveoscleral outflow pathway where does the aqueous humor leave

A

anterior face of ciliary body in the AC angle

41
Q

uveoscleral outflow pathway: 4 key points

A
  1. pressure independent
  2. flows between muscle fibers to supraciliary space
  3. exits via sclera and vortex veins
  4. mostly all glaucoma drugs target this pathway to increase outflow
42
Q

how many layers is the apex of the TM at the schwalbe’s line

A

3-5

43
Q

how many layers is the base that extends into the ciliary body, iris, and scleral spur

A

12-20

44
Q

T/F: the amount of pigment phagocytosed by the trabecular endothelial cells in posterior “filtering” meshwork is greater than the anterior “non filtering” meshwork

A

T

45
Q

the apex of TM may serve as what?

A

stem cells for endothelium lining trabecular beams (NON FILTERING REGION )

46
Q

what are the 3 regions of the TM

A
  1. uveal trabecular meshwork (nearest AC)
  2. corneoscleral meshwork
  3. JCT (cribriform meshwork)
47
Q

the uveal trabecular meshwork region of the TM contains the thinnest or widest spacing between beams

A

widest spacing (25-75 microns side to side)

48
Q

how many layers is the uveal trabecular meshwork

A

only 1-3 layers

49
Q

where does the uveal trabecular meshwork originate

A

the anterior aspect of the ciliary body and iris

50
Q

where does the corneoscleral meshwork originate

A

the scleral spur (8-15 layers)

51
Q

what type of sheets are the corneoscleral meshwork

A

flat perforated sheets

52
Q

how large is the opening in the corneoscleral meshwork

A

2-15 microns (side to side)

53
Q

what is the JCT (cribriform meshwork) composed of and where is it in relation to the corneoscleral sheet

A

composed of fibroblasts and ECM material, elastic fibers – abuts the outermost corneoscleral sheet

54
Q

peripheral iridotomy

A
  • uses a laser beam to create a small hole in your iris
  • this forms a permanent passage through which aqueous humor can flow through and pushes the iris tissue backward, thus unblocking the drainage channels
  • Laser makes a hole in the iris
55
Q

SLT (Selective Laser Trabeculoplasty)

A

small laser (cold laser only absorbed by pigmented tissue) holes are made in TM to increase fluid movement

56
Q

Trabeculectomy

A
  • A wedge of meshwork is surgically removed and a scleral flap is made, aqueous can drain and accumulate to be absorbed into episcleral tissue
  • Can lower IOP by 30%, 1-3 months for results to appear
57
Q

Endoscopic cyclophotocoagulation (ciliary body)

A

reduces aqueous production by using laser to damage tissue of ciliary processes

58
Q

does the C/D ratio increase or decrease in response to primary open-angle glaucoma (POAG)

A

increase

Ocular Anatomy (15 decks)

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