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Glaucoma > Lec.2: Glaucoma Background, Basics and Concepts > Flashcards

Lec.2: Glaucoma Background, Basics and Concepts Flashcards

1
Q

purpose of aqueous humor?

A

provides: shape, optical properties, nourishment to cornea and lens

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2
Q

name the muscles of the ciliary body muscle.

A

longitudinal fibers, circular fibers and radial fibers

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3
Q

what sit eh functional unit that is responsible for production of aqueous humor secretion?

A

ciliary process

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4
Q

what is hypotony?

A

soft eyeball that doesn’t maintain its shape

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5
Q

why is there an absence of protein and lipids in the aqueous fluid?

A

to enhance light transmission

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6
Q

in normal people, when is IOP highest and lowest?

A

highest in AM and lowest in PM

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7
Q

why may IOP spike in the PM for glaucoma patients?

A

because outflow may not be as good as the healthy patient

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8
Q

what enzymes are known to increase the production of aqueous?

A

Na/K-ATPase and carbonic anhydrase

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9
Q

what are the pathways of aqueous humor outflow?

A

trabecular (conventional) or uveoscleral (unconventional) route

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10
Q

name the route of the conventional route.

A

trabecular meshwork–> schelemm’s canal–> lumen –> collector channels–> aqueous veins –>episcleral venous circulation

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11
Q

how is aqueous humor outflow affected if there in an increase in pressure in the episcleral veins?

A

decreases. when laying down episcleral pressure is increased

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12
Q

which rout is can you quite readily decrease IOP?

A

conventional route

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13
Q

how long does it take to notice a large drop in uveoscleral outflow?

A

4-6 weeks

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14
Q

what is the percent of aqueous outflow by the trabecular route?

A

70-95% (main route)

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15
Q

what is the percent of aqueous outflow by the uveoscleral outflow? and which drug enhances outflow of this pathway?

A

5-30%

prostaglandin

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16
Q

is it true that both total and trabecular outflow increase with age?

A

false, they decline with age

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17
Q

what are the four parts that divide the optic nerve head?

A

surface nerve fiber layer, prelaminar region, lamina cribosa region and retrolaminar

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18
Q

in what part of the ONH are axonal bundles acquiring more interaxonal glial tissue?

A

surface nerve fiber layer

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19
Q

what is the predominant sructure of the prelaminar region?

A

nerve axons and astrocytes with signficant increase in astroglial tissue

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20
Q

what region of ONH has fenestrated sheets of scleral tissue that are separated by astrocytes?

A

lamina cribrosa

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21
Q

where in the ONH is there a decrease in astrocytes and myelin is acquired?

A

retrolaminar region

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22
Q

what is the main source of blood supply to the optic nerve?

A

posterior ciliary artery

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23
Q

what is the main blood supply to the surface NFL?

A

CRA (central retinal artery)

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24
Q

what is the main blood supply to the prelaminar and laminar regions?

A

SPCA (short posterior ciliary arteries) which then forms the circle of Zinn-Haller

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25
Q

in poor circulation, which vessels are more responsible for the decrease in circulation?

A

small vessels NOT the large vessels

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26
Q

which vessels cause sudden death of tissue in ischemic optic neuropathies?

A

large vessels

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27
Q

thin astrocytes accompany which axons?

A

axons in NFL

28
Q

thick astrocytes accompany which axons?

A

direct axons from prelaminar to laminar region

29
Q

what is found surrounding the myelin sheaths?

A

hyaluronate

30
Q

how does increase in age and IOP affect hyaluronate?

A

hyaluronate decreases

31
Q

how would the pores of the lamina cribrosa appear in an individual with glaucoma?

A

distorted or compressed pores

32
Q

size of pores (from largest to smallest), follow which rule?

A

ISNT

33
Q

what regions of the NFL do arcuate fibers (Bjerrum’s fibers) occupy?

A

superior and inferior temporal regions

34
Q

do superior fibers cross into the inferior retina and vice-versa?

A

no. imagine a line that separates the two

35
Q

approximately how many axons are we born with?

A

1 million

36
Q

by what age does the ONH reach 95% of its full size?

A

1 yr old

37
Q

is loss of axons based on size (largest are lost first)?

A

no

38
Q

is cupping the absence of tissue?

A

yes

39
Q

what does more cupping and less pallor indicate?

A

glaucoma

40
Q

what is the extent of ocular damage in glaucoma?

A

associated with loss of the neurons that connect to the LGN or visual cortex

41
Q

aside from increase IOP and low blood circulation, what else contributes to glaucoma?

A

aberrant immunity cells and excessive glutamate stimulation

42
Q

which receptors does glutatmate overstimulate to kill off ganglion cells?

A

NMDA receptors and Kainate glutamate receptors

43
Q

what endothelial cell secretes vasodilators?

A

nitric oxide

44
Q

what endothelial cell secretes vasoconstrictors?

A

endothelin-1

45
Q

why should you not use a fundus camera to asses c/d ratio?

A

uses post-processing of the data to adjust the colors (more pink). this leads to false estimates

46
Q

what is considered to be an abnormal inter-ocular c/d asymmetry (between OD and OS)?

A

0.2 or greater

47
Q

how much space should an optic nerve occupy in a 15 degree image?

A

5 degrees of the space

48
Q

what condensing lens gives exactly 1x magnification (spares conversion factors)?

A

66D lens

49
Q

what is considered a large nerve?

A

nerve larger than 2.5

50
Q

what is considered a small nerve?

A

smaller than 1.5

51
Q

what is considered a medium nerve?

A

1.5-2.0

52
Q

how does a grey crescent affect estimation of the rim tissue?

A

leads to underestimation

53
Q

in PPA (peripapillary atrophy) what does the widest region of the crescent correspond too?

A

thinnest rim tissue region

54
Q

what is it called when a optic nerve is completely tilted 90 degrees?

A

tilted disc syndrome (ISNT rule wont work here)

55
Q

what does the scleral lip represent?

A

represents anterior extension of sclera between choroid and optic disc

56
Q

what is zone beta (chrioscleral crescent)?

A

broader, more irregular area of depigmentation. represents retraction of RPE and thinning or absence of choroid

57
Q

what does a large zone beta indicate?

A

higher risk of glaucoma

58
Q

where does rim tissue tend to be thinnest (in reference to zone beta)?

A

where zone beta is widest

59
Q

what is zone alpha?

A

peripapillary crescent of increased pigmentation

60
Q

why does PPA need to be monitored?

A

because it may increase over time (it is an indicator of glaucoma)

61
Q

is presence of hemorrhage enough to initiate treatment for glaucoma?

A

no

62
Q

what is barring?

A

rim becomes thinner and leaves an area (gap) or pallor between the rim and the circumlinear blood vessel

63
Q

when is barring a “hard” sign of glaucoma.

A

is you dont see it when you first examine the patient, but after 3 years they develop barring

64
Q

what is bayonetting (double angulation of blood vessel)?

A

vessels are observed going into the base of the cup, traveling up, and coming out of a different region

65
Q

what is a last ditch effort to save the eye?

A

shunt vessels (due to obstruction of venous flow through distorted lamina cribrosa)

Glaucoma (12 decks)

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