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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

25
TM route is based on pressure gradient between what?
- intraocular pressure (IOP) and episcleral venous pressure (EVP) 15 mmHg vs 7 mmg
26
T/F: Uveoscleral route is pressure dependent
F: Uveoscleral route is pressure independent
27
in the Uveoscleral route, open face of ciliary body band allows for what?
eggression via the space between the ciliary muscle fiber bundles to the supraciliary -- SAS -- from this point multiple ways out
28
how many regions does the TM have and what are they?
29
sustained resistance to outflow usually results in what
elevated IOP
30
what is limbal conjunctiva formed by?
epithelium and loose connective tissue stroma
31
tenons capsule forms what over what?
thin, poorly defined connective tissue over episclera
32
limbal stroma is composed of
scleral and corneal tissues that merge
33
conjunctival stromal vessels form what
peripheral corneal arcades which extend anteriorly to termination of bowmans layer
34
episcleral vessels are cut in different planes and the vessels form what?
intra-scleral and deep scleral are within the limbal stroma
35
sclera spurs have what type of collagen fibers and where are they located
- course/dense collagen fibers - anterior part of the longitudinal portion of the ciliary muscle merges with the scleral spur and TM
36
sheets of TM are outer to
cords of uveal meshwork
37
where does the iris process arise and what does it join
iris surface and join TM a the level of the anterior portion of the scleral spur
38
descemet's membrane terminates where and what does it outline
within the anterior portion of the triangle outline aqueous outflow system
39
Trabecular Route flow
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
in the uveoscleral outflow pathway where does the aqueous humor leave
anterior face of ciliary body in the AC angle
41
uveoscleral outflow pathway: 4 key points
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
how many layers is the apex of the TM at the schwalbe's line
3-5
43
how many layers is the base that extends into the ciliary body, iris, and scleral spur
12-20
44
T/F: the amount of pigment phagocytosed by the trabecular endothelial cells in posterior "filtering" meshwork is greater than the anterior "non filtering" meshwork
T
45
the apex of TM may serve as what?
stem cells for endothelium lining trabecular beams (NON FILTERING REGION )
46
what are the 3 regions of the TM
1. uveal trabecular meshwork (nearest AC) 2. corneoscleral meshwork 3. JCT (cribriform meshwork)
47
the uveal trabecular meshwork region of the TM contains the thinnest or widest spacing between beams
widest spacing (25-75 microns side to side)
48
how many layers is the uveal trabecular meshwork
only 1-3 layers
49
where does the uveal trabecular meshwork originate
the anterior aspect of the ciliary body and iris
50
where does the corneoscleral meshwork originate
the scleral spur (8-15 layers)
51
what type of sheets are the corneoscleral meshwork
flat perforated sheets
52
how large is the opening in the corneoscleral meshwork
2-15 microns (side to side)
53
what is the JCT (cribriform meshwork) composed of and where is it in relation to the corneoscleral sheet
composed of fibroblasts and ECM material, elastic fibers -- abuts the outermost corneoscleral sheet
54
peripheral iridotomy
- 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
SLT (Selective Laser Trabeculoplasty)
small laser (cold laser only absorbed by pigmented tissue) holes are made in TM to increase fluid movement
56
Trabeculectomy
* 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
Endoscopic cyclophotocoagulation (ciliary body)
reduces aqueous production by using laser to damage tissue of ciliary processes
58
does the C/D ratio increase or decrease in response to primary open-angle glaucoma (POAG)
increase

Ocular Anatomy (15 decks)

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