GLAUCOMA 6 - assessment of optic disc in POAG

Question 1

what is glaucoma characterised by??

Answer 1

retinal ganglion cell dysfunction and death

Question 2

before you develop a VF defect, how much of your nerve fibres need to die?

Answer 2

25%

Question 3

what is the OHTS study?

Answer 3

ocular hypertension treatment study 2002

Question 4

in glaucoma, are you more likely to observe an optic disc change or a VF defect??

Answer 4

optic disc change

Question 5

what structure marks the edge of the neuro retinal rim?

Answer 5

Elschning scleral ring

Question 6

which structure haas a yellow-white ‘sieve-like’ appearance?

Answer 6

lamina cribrosa

Question 7

how do you measure disc size?

Answer 7

from the inner part of the rims on either side

Question 8

what is the ISNT rule?

Answer 8

NRR is widest inferior, superior, nasal then temporal

Question 9

what section of the disc is likely to show thinning in glaucoma EARLY STAGES? (isnt rule)

Answer 9

infero-temporal region

Question 10

what section of the disc is likely to show thinning in glaucoma LATE STAGES? (isnt rule)

Answer 10

can be nasal

Question 11

if you have a large disc/scleral opening are you more likely to have a larger or smaller cup?

Answer 11

large cup

Question 12

if you have a small disc/scleral opening, are you more likely to have a larger or smaller cup?

Answer 12

small cup

Question 13

how many nerve fibres are going through the scleral opening of the ONH?

Answer 13

1.2 million

Question 14

what is the scleral canal/opening?

Answer 14

where the nerve fibres run through the optic disc

Question 15

what are the key optic disc changes in glaucoma?

Answer 15

• enlargement of optic cup
• loss of NRR
• vascular changes (haemorrhages and distribution of vessels)
• increased pallor
• peri-papillary atrophy
• RNFL changes

Question 16

if pallor is the biggest change to the optic disc, is glaucoma the only disease to be considered?

Answer 16

NO - consider other optic neuropathies e.g AION
pallor is a late sign in glaucoma

Question 17

is enlargement of the optic cup generalised or localised?

Answer 17

can be both !

Question 18

is vertical cupping or horizontal cupping more indicative of glaucomatous changes?

Answer 18

vertical cupping

Question 19

if you have inter-eye asymmetry, what do you need to check for?

Answer 19

the disc sizes are the same - if not this could be physiological

Question 20

what is the diagnostic accuracy of measuring CD ratios?

Answer 20

poor sensitivity and poor specificity

limited

Question 21

what are the disadvantages of measuring CD ratios?

Answer 21

poor diagnostic accuracy - poor sensitivity/specificity
inter/intra-observer variability

Question 22

what is the lens magnification factor for a superfield?

Answer 22

1.5

Question 23

what is the lens magnification factor for a 66D volk?

Answer 23

1.0

Question 24

what is the lens magnification factor for a 90D volk?

Answer 24

1.4

Question 25

what is the lens magification factor for a 78D volk>

Answer 25

1.1

Question 26

when assessing VFs, you need to look for asymmetry...

Answer 26

between the 2 eyes AND between the superior and inferior hemi fields (GHT)

Question 27

what are the vascular changes that can occur in glauc?

Answer 27

- vessel configuration (nasalisation, bayonetting, flyover/overpass, circumlinear bearing) - calibre of vessels can be thinner at optic disc - collateral vessels - haemorrhage

Question 28

what are collateral vessels?

Answer 28

occur when someone has had a CRVO which can be associated with high IOP OPTOCILIARY SHUNT VESSELS

Question 29

what are the main changes you need to be looking for when assessing if a disc is glaucomatous or not?

Answer 29

cupping changes and thinning of NRR

Question 30

a disc haemorrhage is a sign of..

Answer 30

active progression

Question 31

which type of glaucoma are disc haemorrhages common in?

Answer 31

NTG

Question 32

other than glaucoma what is a common cause for a disc haemorrhage?

Answer 32

PVD

Question 33

are haemorhhages constantly there?

Answer 33

no - they can be reabsorbed

Question 34

what does this image show?

Answer 34

disc haemorrhage

Question 35

what does this image show?

Answer 35

disc haemorrhage, little cupping could be due to PVD

Question 36

what does this image show?

Answer 36

large inferior haemhorrhage

Question 37

what does this image show?

Answer 37

superior haemorrhage in thte RNFL as it is radiating away from disc

Question 38

you can get peri-papillary atrophy in 2 zones - what are these called?

Answer 38

alpha zone and beta zone

Question 39

out of aloha and beta zones, which is worse??

Answer 39

beta (remember B for BAD)

Question 40

what is peri-papillar atropy associated with?

Answer 40

NRR loss and VF defect

Question 41

what do these images show?

Answer 41

peri-papillary atrophy

Question 42

optic disc checklist!!

Answer 42

- Is the vertical C/D ratio >0.5? - Is the C/D ratio consistent with disc size? - Is the cup more vertically oval than the disc? - Does rim configuration differ from ‘ISNT’? - Are there any notches or pallor regions in the nrr? - Are there any disc haemorrhages ? - Is the inter-eye C/D ratio asymmetry >0.2? - Has there been a >0.15 change in C/D ratio?

Question 43

CD ratio??

Answer 43

0.7-0.85 (about 1.5 difference per person)

Question 44

what is the DDLS?

Answer 44

disc damage likelihood scale

Question 45

how do you grade the disc size according to DDLS?

Answer 45

measure disc size (correct for volk magnification) small = <1.5mm medium = 1.5-2 mm large = >2.0mm

Question 46

how do you measure width of thinnest part of the rim for DDLS?

Answer 46

rim - disc ratio if no rim oresent at thinning part = 0 if rim as thick as possible (no cup) = 0.5

Question 47

IF YOU HAVE SEEN PX BEOFRE how much difference in the CD ratio does there need to be for you to say there has been a change??

Answer 47

0.15

Question 48

IF YOU HAVEN'T SEEN PX BEFORE how much difference in the CD ratio does there need to be for you to say there has been a change?

Answer 48

0.25

Question 49

what does this image show?

Answer 49

optic atrophy

Question 50

what does this image show?

Answer 50

RNFL assessment - inferior cupping with notched rim dark shadow extending inferior temporally from the disc = nerve fibre layer defect

Question 51

what does this image show?

Answer 51

wedge-like defect in RNFL associated with inferior VF defect in the Px's RE

Question 52

what does this image show?

Answer 52

wedge-like defect in RNFL associated with inferior VF defect in the Px's RE

Question 53

which 3 systems are good for imaging the optic nerve head?

Answer 53

OCT heidelberg retina tomograph (HRT) GDx VCC

Question 54

if you have an abnormal finding on one machine, does that mean they have glaucoma??

Answer 54

NO - need to asses all clinical information together

Question 55

what does this image show?

Answer 55

pseudoexfoliation in the lens = flakes and sheets of exfoliative material can be cause of secondary glaucoma

Question 56

what are some examples of congenital disc abnormalities?

Answer 56

coloboma optic disc pit tilted disc drusen myelinated fibres myopic disc

Question 57

what does this image show?

Answer 57

myopic disc

Question 58

what does this image show?

Answer 58

tilted disc potentially has glaucoma as well

Question 59

what does this image show?

Answer 59

optic disc drusen

Question 60

other than glacuoma, what other conditions can cause nerve fibre bundle defects?

Answer 60

- optic nerve head drusen - congenital optic nerve head pits - coloboma of optic nerve - AION - tilted disc

Question 61

is this disc physiological or pathological?

Answer 61

physiological- ISNT rule is followed,

Question 62

is this disc physiological or pathological?

Answer 62

pathological - superior rim is thinner than temporal, vertically excavated

Question 63

what does this image show?

Answer 63

Question 64

what does this image show?

Answer 64

Question 65

what does this image show?

Answer 65