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OD3 (S1&2) > DIS - Glaucoma Assessment Tutorial I - Week 4 > Flashcards

DIS - Glaucoma Assessment Tutorial I - Week 4 Flashcards

1
Q

What is the standardised testing protocol for all glaucoma suspects (5)? List six additional supplementary tests you can do.

A

Standard protocol
Pachymetry
Gonioscopy
Disc photos
OCT
Visual fields
Supplementary
Corneal hysteresis
ERG and VEP
Computerised colour vision testing
Pupilography
OCTa

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2
Q

List the 8 stages of glaucom in the leadup to blindness. List a test or symptom that can detect when a patient is at this stage if applicable (5).

A

Normal
Acceleration of apoptosis
Ganglion cell death
-macular GGC scan
RNFL change (undetectable)
RNFL change (detectable)
-optic nerve RNFL scan
SWAP VF changes
-humphrey/medmont
SAP VF change
-arcuate/nasal step/paracentral/temporal wedge
VF change (moderate)
VF change (severe)
-tunnel vision
Blindness

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3
Q

Is IOP useful in the detection and assessment of glaucoma?

A

Not useful in detection but very useful in assessment and treatment planning

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4
Q

Is IOP more variable in normals or glaucoma patients?

A

Glaucoma patients
It is still variable in normals

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5
Q

What is the ebst way to get a diurnal IOP curve for a glaucoma suspect?

A

Schedule appointments at different times of the day and measure IOP each time

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6
Q

Is it advisable to complete glaucoma assessment entirely in one appointment or schedule it across different visits?

A

Best not to do it all at once
Schedule for different times of the day and measure IOP each time

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7
Q

Keeping the variability of IOP and diurnal curve in mind, what is considered the baseline IOP when treating glaucoma patients?

A

The highest pressure recorded prior to treatment

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8
Q

What is the average measurement for ultrasound pachymetry?

A

555 microns

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9
Q

List the measurements for the following thicknesses of the cornea:
Thick
Nornal
Thin
Very Thin

A

Thick - 590 microns
Nornal - 555 - 590 microns
Thin - 525 - 555 microns
Very Thin - <525 microns

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10
Q

Describe which of the following IOP and cornea thickness combinations is a risk factor for glaucoma:
Low IOP, thin pachymetry
High IOP, thick pachymetry
Low IOP, thick pachymetry
High IOP, thin pachymetry

A

Low IOP, thin pachymetry - no problem
High IOP, thick pachymetry - no problem
Low IOP, thick pachymetry - no problem
High IOP, thin pachymetry - risk factor

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11
Q

Do thick corneas under-estimate or over-estimate IOP? What about thin corneas?

A

Thin - under-estimates
Thick - over-estimates

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12
Q

Is CCT a dependent or independent risk factor for glaucoma? Explain why by describing what it is a surrogate measure of.

A

Independent risk factor - it is a surrogate measure of the lamina cribrosa thickness

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13
Q

Can IOP be corrected or adjusted based on pachymetry?

A

No, the relationship is non-linear

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14
Q

What is the strongest predictor of the conversion from ocular hypertension to glaucoma? Is this a better predictor than C/D ratio and VF?

A

Thin pachymetry is the strongest predictor

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15
Q

What three key pieces of information does gonioscopy provide on a glaucoma suspect?

A

How narrow the angle is
If there are any restrictions to outflow
Most appropriate glaucoma treatment plan

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16
Q

Consider the five structures that may be visible in gonioscopy. Visibility of which of these is considered an open angle and which are occludable?

A

Ciliary body, scleral spur, and PTM are open angles
ATM and schwalbes line are occulable

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17
Q

Describe the gonioscopy classification of a primary angle suspect (2) and the chance of progressing to primary open angle glaucoma in 5 years.

A

PTM not visible in two or more mirrors without indentation
Opens fully on indentation
~20% chance of progress to glaucoma

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18
Q

Describe the gonioscopy classification of a primary angle closure (3).

A

PTM not visible in two or more mirriors
PAS present
Signs of ischaemia
-glaucomflecken

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19
Q

Describe the gonioscopy classification of a primary angle closure glaucoma (6).

A

PTM not visible in two or more mirriors
PAS present
Signs of ischaemia
-glaucomflecken
Optic nerve damage
RNFL loss
VF defect

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20
Q

What is glaucomflecken and why does it occur? Explain where it occurs specifically and why. What does it occur secondary to?

A

Central anterior cortical cataract only within the pupil zone
Occurs due to the lack of aqueous flow to the anterior lens, secondary to a pupil block
Lens becomes hypoxis and cataracts occurs only in that area

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21
Q

List 4 limitations of AS-OCT compared to gonioscopy.

A

OCT can only show the anatomy in a single cross section
OCT cannot easily detect PAS
OCT cannot do indentation
OCT cannot give information on outflow (pigment/PXF)

22
Q

What is the best way to document the appearance of the disc and RNFL? What does this aid in?

A

Take photos
Aids in detecting change over time
Can occasionally detect changes ahead of OCT and VF testing

23
Q

What is an OCT A-scan? What is its glaucoma clinical value and what is it useful for (2)?

A

Retinal thickness at a single point
Limited glaucoma clinical value
Useful for axial length (myopia) and IOL power

24
Q

What is an OCT B-scan? What can be done to increase its resolution?

A

Multiple adjacent A-scans in a row
-is a cross sectional slice through the retina
Repeated B-scans at the same location increases resolution

25
Q

What are rasters?

A

Widely spaced B-scans

26
Q

What type of OCT scans are the most useful in glaucoma? Give a limitation of this type of scan.

A

3D maps/cubes are most useful for glaucoma
Each B-scan is only taken once
-low resolution

27
Q

What type of B-scan is better for the RNFL around the ONH?

A

Circular B scan

28
Q

True or false
Glaucoma in all forms leads to ganglion cell loss

A

True

29
Q

What is the RNFL made up of (1)? What about ganglion cells (3)? What about the GCC and what is the average thickness?

A

RNFL is made up of ganglion cell axons
Ganglion cells are made up of the IPL, GCL, and NFL
All three together form the GCC
-avergae thickness is 100 microns, each component a third

30
Q

In what way do ganglion cells begin to die in glaucoma? Describe the sequence (4). Keeping this in mind, does it matter if the gnaglion cell injury is internal or external?

A

They die in a characteristic way
-first the synapses to bipolar cells at the IPL break down (loss of dendritic arbour)
-disruption of microtubules in the axons occurs, impeding signal flow to the brain
-the soma dies, causing GCL thinning
-phagocytosis of the axons, causing thinning of the RNFL
If the cell injury is internal (IOP) or external (axotomy), the cells die the same way

31
Q

Keeping in mind the way ganglion cells die, where would the first signs of structural damage be? Where does majority of this occur on the retina?

A

At the synapses and cell bosies
80% of these synapses occur in the central 9mm of the retina, not near the disc

32
Q

Keeping in mind the way ganglion cells die, measuring ganglion cell thickness at which area of the macula should provide the earliest sign of ganglion cell loss?

A

The macula

33
Q

List two limitations of GCC scans.

A

Even though 80% of retinal ganglion cells are in the macula, GCC only samples temporal to the disc (no nasal information)
RNFL scan only measures axons but samples all 360 degrees of the disc

34
Q

Can GCC scans be used with any co-morbidity that disrupts the retina?

A

No

35
Q

List three limitations of RNFL scans.

A

High variability in the normal population due to variable disc anatomy
Poor reproducibility even on the same day due to vascular pulsation
No measure ganglion cell synapse or cell bodies

36
Q

List four this that confound RNFL scan quality.

A

Numerous blood vessels around the disc
Peripapillary floaters
Posterior hyaloid membrane
More difficult for patients to fixate laterally

37
Q

Which is better, GCC or RNFL scans? Should you always do both in clinical practice?

A

Some studies sow GCC is better, others show no difference
Should always do both scans

38
Q

What do the following colours mean on OCT GCC and RNFL scans mean?
Green
Yellow
Red

A

Green - 5-95% of the population
Yellow - 1-5%
Red - 0-1%

39
Q

Do all instruments have false positives?

A

Yesd

40
Q

What is the False positive rate for OCTs?

A

Up to 25%

41
Q

Define red disease, why it happens, and what it could be due to (4).

A

OCT flagged in red but no actual disease
Is due to the patient being different to the normative database
-database is limited in number, gender, race, age etc
Also due to artefacts, blinking, floaters, eye movements etc

42
Q

Define green disease and why it happens. What should be done in these cases?

A

OCT flagged in green but is actually diseased
Green covers 5-95%
One eye could be 6% and the other could be 95% with both green
Dont look at colours alone, look at the data

43
Q

Should OCT be used in routine care on every patient to search for glaucoma suspects? Explain (3).

A

Due to high risk of flase positives, it shouldnt be used in routine care
Will incorrectly flag too many patients as glaucoma suspects
These patients need to be investigated, often referred to ophthalmologists
Waste of resources and unnecessary worry
-only use in the assessment of glaucoma suspects already detected using results from routine eye exams

44
Q

Are supplementary tests for glaucoma detection reimbursed by medicare?

A

No, because they are experimental in nature

45
Q

What does corneal hysteresis measure and what does it predict (3)?

A

Airpuff test measuring the speed of rebound
Low hysteresis is predictive of:
-which glaucoma suspect will develop glaucoma
-increased risk of glaucoma progression
-more rapid RNFL loss over time

46
Q

What do ERG and VEP measure and what are they an alternative to? How are they in terms of time to complete and availability?

A

Can measure sensitivity in different retinal locations
Objective alternative to visual fields for functional evaluation
Time consuming
Limited availability

47
Q

What does computerised colour vision testing assess and why?

A

Glaucoma typically causes acquired tritan defects

48
Q

What colour ganglion cells are least populous in the retina?

A

Blue-yellow
Reasoning behind selective blue-yellow HFA perimetry

49
Q

Does automated pupilography detect all optic neurpathies or is it just specific to glucoma?

A

Detects all of them
Glaucoma is the most common optic neuropathy

50
Q

How can automated pupilography be used to assess bilateral simultaneous VFs? Explain.

A

Pinpoint sectors of light are projected to different parts of the retina
Pupil reaction is measured
Areas of reduced sensitivity are plotted

OD3 (S1&2) (114 decks)

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