Lecture 2: Background & Basics Flashcards
(88 cards)
1
Q
What is aqueous humor useful for?
A
- shape
- optical properties to globe
- nourishment to cornea and lens
2
Q
why does iop go up when we age?
A
because our removal of AH declines
3
Q
The long fibers attach ___ to ___
A
Cb; limbus
4
Q
The circular fibers are responsible for the anterior and inner portions of ____
A
CB
5
Q
The radial fibers connect ____ fibers and the _____ fibers
A
longitudinal; circular
6
Q
What are the 3 CB vessels
A
- Episcleral circle
- intramuscular circle
- Major arterial circle
7
Q
What two branches of the major arterial circle are responsible for supplying the ciliary process
A
- anterior ciliary process arteriole
2. posterior ciliary process arteriole
8
Q
what is the functional unit responsible for production of aqueous humor secretion?
A
ciliary process
9
Q
what 3 things are the ciliary process made of
A
- capillaries
- stroma
- epithelia
10
Q
why is it important that capillaries occupy the center of each process?
A
occupies center for filtration mechanism to take place which allows for AH production
11
Q
how is aqueous fluid controlled?
A
carefully controlled filtrate of blood produced by CB
12
Q
what is aqueous fluid a source of for the corneal endothelium and the lens?
A
antioxidants
13
Q
aqueous fluid also serves as a ____absorber
A
shock
14
Q
what is absent in AH?
A
hemoglobin
15
Q
which vitamin is found greater in AH
A
C
16
Q
Protein and ____ are very low in AH
A
calcium
17
Q
how is AH formed?
A
it is secreted by ciliary epithelium of ciliary process and enters posterior chamber via diffusion, ulftrafiltration, and secretion
18
Q
when is AH production greatest
A
in the morning-noon
19
Q
when is AH production the lowest
A
midnight- 6 am
20
Q
when is IOP the highest
A
late night midnight to 6 am
21
Q
aqueous formation is an active process that works ____concentration gradient
A
against
22
Q
which enzymes are responsible for aqueous formation
A
- Na
- K-ATPase
- carbonic anhydrase
23
Q
what are the two ways that AH can leave eye?
A
- uveoscleral
2. trabecular or conventional route (majority)
24
Q
describe the route of the conventional route
A
TM –> inner wall of schemes canal into its lumen –> collector channels, aqueous veins and episcleral venous circulation.
25
describe the route of the uveoscleral route
across iris root --> uveal meshwork and the anterior face of ciliary muscle --> through the CT between the muscle bundles, through suprachoroidal space --> out through sclera
26
what are the ways in which IOP can be decreased?
1. decreasing production of AH
| 2. enhancing conventional route
27
If you want to decrease pressure right away which route do you want to target?
conventional route
28
#1 drugs used to target glaucoma target the _____ outflow
uveoscleral
29
What happens in diseases or trauma within the blood aqueous barrier?
plasma components enter the AC into the aqueous humor and net inflow of fluid from the blood the aqueous increases
30
what does pseudo facility refer to
when IOP increases, aqueous inflow by ultrafiltration is suppressed, slowing down the rise in IOP thus providing some measure of protection. (no removal of fluid, but overall production has dropped).
31
what four parts are the optic nerve head divided into
1. surface NFL
2. prelaminar region
3. lamina cribrosa region
4. retrolaminar region
32
which region has fenestrated sheets of scleral connective tissue
lamina cribrosa region
33
which artery is responsible for the mainly supply to the optic nerve
posterior ciliary artery
34
NFL is supplied by ____ circulation via arteriolar branches of the CRA
retinal
35
blood vessel supply to the preliminary and laminar region are via the _____
SPCA
36
T/F? the more disease you have, the fewer amount of capillaries you have
true
37
venous drainage is via the _____
central retinal vein
38
thin astrocytes accompany the axons in the _____, thick axons direct axons from the prelaminar to the laminar region.
NFL
39
glaucoma pathogenesis takes place at the level of:
lamina cribrosa
40
how do you get lamina dot signs
pores get compressed, axons get crushed and "suffer"
41
why is the inferior thickest?
lots of arcuate and papillomacular fibers here
42
what are two reasons that central vision is protected even in advances cases of glaucoma?
1. fibers intermingle with other fibers.
| 2. macula has disproportianate number of fibers to begin with.
43
Axons range from ____ to 1.2 million
700,000
44
We get a progressive loss of axons from 4,000 to ____axons a year
12,000
45
The ____ ____ has greater susceptibility to damage, but it has potential for reversible cupping
lamina cribrosa
46
The size of the ONH is ___% before age 1
95
47
Glaucoma is a neurodegenerative disease characterized by the slow, progressive degeneration of retinal _____ cells
ganglion
48
T/F Glaucoma damage is not limited to retinal ganglion cell axons, soma and dendrites.
True; neurons in LGN and visual cortex are also lost.
49
T/F If pallor > cupping then glaucomatis optic neuropathy.
| If cupping > pallor then possible optic neuropathy
true
50
what are factors contributing to the pathophysiology in glaucoma
1. ischemia
2. high iop
3. inflammatory cytokines
4. excessive glutamate stimulation
5. blockade of neurotrophic and other target derived factors
51
what are two theories for the cause of glaucoma
1. elevated iop cause direct compression and death.
| 2. vascular abnormalities cause optic atrophy.
52
what happened when researchers injected glutamate subcutaneously and intravitreally?
death of retinal ganglion cell's
53
there was glutamate mediated cell death when there was an overstimulaiton of____ receptors and ____ receptors
NMDA; kainate
54
RGC survival depends upon certain neuronal growth factors called:
neurotrophins
55
what is beneficial at certain concentrations as a vasodilator but neurotoxic in higher concentrations
nitric oxide
56
what is the mechanical theory
physical alterations, misalignment of fenestrae backbowing of lamina cribrosa may lead to obstruction. Compression of ganglion cell axon impairs the trophic factor axonal flow transport causing death of cell. Damage with elevated IOP occurs despite intact blood vessels
57
what is the vascular theory
ischemia at least plays a role in the obstruction of axoplasmic flow in response to elevated IOP. Retina depends on good blood flow for its metabolic needs. There is a dysfunction in auto regulation
58
mean ocular perfusion pressure is mean ____ minus ____
BP; IOP
59
what are two types of auto regulatory mechanisms
1. metabolic
| 2. myogenic
60
In metabolic mechanism endothelial cells secrete nitric oxide (vasodilators) and _____ 1. (vasoconstrictor)
endothelin
61
What are the evidences that support vascular theory
1. delayed filling of superficial vessels of optic nerve in glaucoma.
2. association of normal tension glaucoma with migraines.
3. excessive peripheral constriction of vessels to cold - Raynauds phenomenon
4. nocturnal blood glow different in glaucoma patients.
5. greater plasma concentration of endothelin -1
62
The _____ theory states that both mechanisms that is vascular and mechanical damage plays a role in glaucomatous pathology.
mechanovascular
63
Regardless of mechanism of damage to retinal ganglion cells - death of RGC in glaucoma is ultimately via ____
apoptosis --> cell death
64
what are the 3 ways that apoptosis occurs
1. photoreceptors secondary to excessive light exposure
2. conjunctival cells secondary to ocular preservatives.
3. corneal eptithelal/keratocytic cells after wounding
65
Describe the apoptosis process
1. cell decreases size; contents become concentrated.
2. nucleus fragments.
3. cell separates into separate small bodies.
4. these are phagocytes without an inflammatory response.
66
What is the conclusion on whether the mechanical or vascular factors are primary
obstruction of axoplasmic flow may be involved in pathogenesis of glaucoma but it is not clear whether mechanical or vascular factors are primary.
67
The neural ____ is the tissue responsible for cupping and loss of visual field.
rim
68
T/F Cup to disc ratio is an indirect measure because large diameter nerve head may be associated with thinner rim but stable number of neurons.
true
69
T/F Larger area disc area correlates positively neural rim
true; more concerned with smaller nerve and smaller cupping than larger nerve with larger neural rim
70
How much space does an average nerve occupy?
5-7 degrees; 3 nerves placed horizontally side by side
71
what is commonly seen in ONH in patients who have myopia
1. vertical - oval shape
2. thinning of temporal neural rim
3. prominent peripapillary halo
72
A myopic nerve is usually _____ not a tilted disc.
malinserted
73
How do you manage patients with tilted disc syndrome
Look at average NFL and check visual fields. If its normal = fine.
74
What does visibility of NFL correlate with
width of neural rim and caliber of retinal artery. The thicker the rim, the more fibers you see.
75
As far as peripapillary pigment variation goes, what represents anterior extension of sclera between choroid and optic disc and is a thin, evenly white, and goes around 360 degrees
scleral lip
76
As far as peripapillary pigment variation goes what is a broader more irregular area of depigmentation and represents a retraction of RPE and thinning/absence of choroid.
chorioscleral crescent/zone beta
77
A greater zone ____ area to disc ratio is found to be associated with greater risk of glaucomatous damage.
beta
78
zone ____ represents peripapillary crescent of increased pigmentation. it represents malposition of embryonic fold with double layer or irregularity of RPE.
alpha
79
Clinically, the widest region of peripapillary atrophy correlate with?
the thinnest rim tissue
80
what is indicative of a notch?
absence of rim tissue, and blood vessel usually goes to edge of disc.
81
what is hemorrhage usually associated with?
progressive damage of the nerve. Also, hemorrhage damage is not limited to only the region of hemorrhage but it can occur anywhere in the nerve...need to monitor carefully.
82
what is barring of circumlinear vessels?
when you see a gap between blood vessel and rim tissue. Vessels should be running supero and infero temporally. As rim becomes thinner it leaves an area of pallor between the rim an the circumlinear blood vessel. No reason of it do this unless it had support at some point.
83
what is nasal cupping
usually seen in advanced glaucoma. You usually see a massive gap between nasal rim and blood vessels.
84
what does laminar dot sign mean
pressure of eye is pushing lamina behind and causing pores to get stretched.
85
what does bayonetting mean
"double angulation of blood vessel." when you look at a blood vessel, it goes in one angle and comes out of another part of the rim.
86
what is commonly seen after hemorrhaging
NFL bundle defects.
87
what does it mean to have shunt vessels
advanced glaucomatous change because of the obstruction of the venous flow through distorted lamina cribrosa.
88
How accurate is ISNT rule of rim
70%
