Lec.2: Glaucoma Background, Basics and Concepts

Question 1

purpose of aqueous humor?

Answer 1

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

Question 2

name the muscles of the ciliary body muscle.

Answer 2

longitudinal fibers, circular fibers and radial fibers

Question 3

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

Answer 3

ciliary process

Question 4

what is hypotony?

Answer 4

soft eyeball that doesn’t maintain its shape

Question 5

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

Answer 5

to enhance light transmission

Question 6

in normal people, when is IOP highest and lowest?

Answer 6

highest in AM and lowest in PM

Question 7

why may IOP spike in the PM for glaucoma patients?

Answer 7

because outflow may not be as good as the healthy patient

Question 8

what enzymes are known to increase the production of aqueous?

Answer 8

Na/K-ATPase and carbonic anhydrase

Question 9

what are the pathways of aqueous humor outflow?

Answer 9

trabecular (conventional) or uveoscleral (unconventional) route

Question 10

name the route of the conventional route.

Answer 10

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

Question 11

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

Answer 11

decreases. when laying down episcleral pressure is increased

Question 12

which rout is can you quite readily decrease IOP?

Answer 12

conventional route

Question 13

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

Answer 13

4-6 weeks

Question 14

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

Answer 14

70-95% (main route)

Question 15

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

Answer 15

5-30%

prostaglandin

Question 16

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

Answer 16

false, they decline with age

Question 17

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

Answer 17

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

Question 18

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

Answer 18

surface nerve fiber layer

Question 19

what is the predominant sructure of the prelaminar region?

Answer 19

nerve axons and astrocytes with signficant increase in astroglial tissue

Question 20

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

Answer 20

lamina cribrosa

Question 21

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

Answer 21

retrolaminar region

Question 22

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

Answer 22

posterior ciliary artery

Question 23

what is the main blood supply to the surface NFL?

Answer 23

CRA (central retinal artery)

Question 24

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

Answer 24

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

Question 25

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

Answer 25

small vessels NOT the large vessels

Question 26

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

Answer 26

large vessels

Question 27

thin astrocytes accompany which axons?

Answer 27

axons in NFL

Question 28

thick astrocytes accompany which axons?

Answer 28

direct axons from prelaminar to laminar region

Question 29

what is found surrounding the myelin sheaths?

Answer 29

hyaluronate

Question 30

how does increase in age and IOP affect hyaluronate?

Answer 30

hyaluronate decreases

Question 31

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

Answer 31

distorted or compressed pores

Question 32

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

Answer 32

ISNT

Question 33

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

Answer 33

superior and inferior temporal regions

Question 34

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

Answer 34

no. imagine a line that separates the two

Question 35

approximately how many axons are we born with?

Answer 35

1 million

Question 36

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

Answer 36

1 yr old

Question 37

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

Answer 37

no

Question 38

is cupping the absence of tissue?

Answer 38

yes

Question 39

what does more cupping and less pallor indicate?

Answer 39

glaucoma

Question 40

what is the extent of ocular damage in glaucoma?

Answer 40

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

Question 41

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

Answer 41

aberrant immunity cells and excessive glutamate stimulation

Question 42

which receptors does glutatmate overstimulate to kill off ganglion cells?

Answer 42

NMDA receptors and Kainate glutamate receptors

Question 43

what endothelial cell secretes vasodilators?

Answer 43

nitric oxide

Question 44

what endothelial cell secretes vasoconstrictors?

Answer 44

endothelin-1

Question 45

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

Answer 45

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

Question 46

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

Answer 46

0.2 or greater

Question 47

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

Answer 47

5 degrees of the space

Question 48

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

Answer 48

66D lens

Question 49

what is considered a large nerve?

Answer 49

nerve larger than 2.5

Question 50

what is considered a small nerve?

Answer 50

smaller than 1.5

Question 51

what is considered a medium nerve?

Answer 51

1.5-2.0

Question 52

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

Answer 52

leads to underestimation

Question 53

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

Answer 53

thinnest rim tissue region

Question 54

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

Answer 54

tilted disc syndrome (ISNT rule wont work here)

Question 55

what does the scleral lip represent?

Answer 55

represents anterior extension of sclera between choroid and optic disc

Question 56

what is zone beta (chrioscleral crescent)?

Answer 56

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

Question 57

what does a large zone beta indicate?

Answer 57

higher risk of glaucoma

Question 58

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

Answer 58

where zone beta is widest

Question 59

what is zone alpha?

Answer 59

peripapillary crescent of increased pigmentation

Question 60

why does PPA need to be monitored?

Answer 60

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

Question 61

is presence of hemorrhage enough to initiate treatment for glaucoma?

Answer 61

no

Question 62

what is barring?

Answer 62

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

Question 63

when is barring a "hard" sign of glaucoma.

Answer 63

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

Question 64

what is bayonetting (double angulation of blood vessel)?

Answer 64

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

Question 65

what is a last ditch effort to save the eye?

Answer 65

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