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Eye Disease > GLAUCOMA 6 - assessment of optic disc in POAG > Flashcards

GLAUCOMA 6 - assessment of optic disc in POAG Flashcards

1
Q

what is glaucoma characterised by??

A

retinal ganglion cell dysfunction and death

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2
Q

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

A

25%

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3
Q

what is the OHTS study?

A

ocular hypertension treatment study 2002

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4
Q

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

A

optic disc change

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5
Q

what structure marks the edge of the neuro retinal rim?

A

Elschning scleral ring

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6
Q

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

A

lamina cribrosa

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7
Q

how do you measure disc size?

A

from the inner part of the rims on either side

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8
Q

what is the ISNT rule?

A

NRR is widest inferior, superior, nasal then temporal

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9
Q

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

A

infero-temporal region

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10
Q

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

A

can be nasal

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11
Q

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

A

large cup

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12
Q

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

A

small cup

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13
Q

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

A

1.2 million

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14
Q

what is the scleral canal/opening?

A

where the nerve fibres run through the optic disc

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15
Q

what are the key optic disc changes in glaucoma?

A
  • enlargement of optic cup
  • loss of NRR
  • vascular changes (haemorrhages and distribution of vessels)
  • increased pallor
  • peri-papillary atrophy
  • RNFL changes
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16
Q

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

A

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

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17
Q

is enlargement of the optic cup generalised or localised?

A

can be both !

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18
Q

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

A

vertical cupping

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19
Q

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

A

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

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20
Q

what is the diagnostic accuracy of measuring CD ratios?

A

poor sensitivity and poor specificity

limited

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21
Q

what are the disadvantages of measuring CD ratios?

A

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

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22
Q

what is the lens magnification factor for a superfield?

A

1.5

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23
Q

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

A

1.0

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24
Q

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

A

1.4

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25
Q

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

A

1.1

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26
Q

when assessing VFs, you need to look for asymmetry…

A

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

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27
Q

what are the vascular changes that can occur in glauc?

A
  • vessel configuration (nasalisation, bayonetting, flyover/overpass, circumlinear bearing)
  • calibre of vessels can be thinner at optic disc
  • collateral vessels
  • haemorrhage
28
Q

what are collateral vessels?

A

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

29
Q

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

A

cupping changes and thinning of NRR

30
Q

a disc haemorrhage is a sign of..

A

active progression

31
Q

which type of glaucoma are disc haemorrhages common in?

A

NTG

32
Q

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

A

PVD

33
Q

are haemorhhages constantly there?

A

no - they can be reabsorbed

34
Q

what does this image show?

A

disc haemorrhage

35
Q

what does this image show?

A

disc haemorrhage, little cupping
could be due to PVD

36
Q

what does this image show?

A

large inferior haemhorrhage

37
Q

what does this image show?

A

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

38
Q

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

A

alpha zone and beta zone

39
Q

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

A

beta
(remember B for BAD)

40
Q

what is peri-papillar atropy associated with?

A

NRR loss and VF defect

41
Q

what do these images show?

A

peri-papillary atrophy

42
Q

optic disc checklist!!

A
  • 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?
43
Q

CD ratio??

A

0.7-0.85 (about 1.5 difference per person)

44
Q

what is the DDLS?

A

disc damage likelihood scale

45
Q

how do you grade the disc size according to DDLS?

A

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

46
Q

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

A

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

47
Q

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??

A

0.15

48
Q

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?

A

0.25

49
Q

what does this image show?

A

optic atrophy

50
Q

what does this image show?

A

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

51
Q

what does this image show?

A

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

52
Q

what does this image show?

A

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

53
Q

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

A

OCT
heidelberg retina tomograph (HRT)
GDx VCC

54
Q

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

A

NO - need to asses all clinical information together

55
Q

what does this image show?

A

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

56
Q

what are some examples of congenital disc abnormalities?

A

coloboma
optic disc pit
tilted disc
drusen
myelinated fibres
myopic disc

57
Q

what does this image show?

A

myopic disc

58
Q

what does this image show?

A

tilted disc potentially has glaucoma as well

59
Q

what does this image show?

A

optic disc drusen

60
Q

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

A
  • optic nerve head drusen
  • congenital optic nerve head pits
  • coloboma of optic nerve
  • AION
  • tilted disc
61
Q

is this disc physiological or pathological?

A

physiological- ISNT rule is followed,

62
Q

is this disc physiological or pathological?

A

pathological - superior rim is thinner than temporal, vertically excavated

63
Q

what does this image show?

A
64
Q

what does this image show?

A
65
Q

what does this image show?

A

Eye Disease (48 decks)

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