DIS - Glaucoma Assessment Tutorial II - Week 5

Question 1

What is better at discriminating glaucoma suspects from glaucoma patients, OCT or stero photos?

Answer 1

OCT

Question 2

Is it common or rare to find simultaneous defects in both structures and function at diagnosis?

Answer 2

Rare

Question 3

What is the issue of correpating structure and function of the ganglion cells? Describe in terms of VF sensitivity.

Answer 3

The variability in ganglion cell density as we move away from the fovea

Question 4

How much does a 3dB point reduction in VF sensitivity correlate with the number of ganglion cells outside the macula and the perifovea?

Answer 4

10 ganglion cells outside the macula
230 ganglion cells in the perifovea

Question 5

Once a field defect is present, is progression better detected by VF changes or disc changes?

Answer 5

VF changes

Question 6

Comparing structure vs function (VF), which is better at detecting early glaucoma? what about more advanced glaucoma?

Answer 6

Structure better at detecting early glaucoma
VFs better for advanced glaucoma

Question 7

Comparing OCT vs function (VF), which is better at detecting early glaucoma? what about more advanced glaucoma? Keeping this in mind, what is the danger of using only one of these techniques (ie. OCT because its quicker)?

Answer 7

OCT better at detecting early glaucoma
VFs better for advanced glaucoma
-significant number of cases missed by either of the above alone
-dont be tempted to use only one technique

Question 8

How many test points does the 30-2 have? Give one advantage and two disadvantages.

Answer 8

76
Advantage - more points in the temporal field
Disadvantage - longer test time, variable threshold of outer ring of points

Question 9

How many test points does the 24-2 have? Give three advantages.

Answer 9

54
Advantages
-still tests out to 30 degrees in the nasal step region
-quicker test time
minimises outer ring variability

Question 10

How many test points does the 10-2 have? Is there strong or weak evidence of central defects early in the disease process? What is this VF setup used to assess? What is its test time like?

Answer 10

68 (in the central 10 degrees)
Strong evidence of central defects early in the diease process
Used to quantify any defects of central 4 points on 24-2 or 30-2
Much longer test time

Question 11

What does the evidence comparing 30-2 and 24-2 suggest in terms of best compromise for speed, comfort, and reliable data?

Answer 11

24-2 in most cases gives the best compromise while being comparable to 30-2

Question 12

Consider the visual field area tested by 10-2. What quadrants are affected first in glaucoma (2)?

Answer 12

Inferotemporal and superotemporal

Question 13

When is the temporal disc often affected in glaucoma? What about the nasal quadrant of the disc?

Answer 13

Not until later in the disease
The nasal quadrant is last

Question 14

True or false
Central VF defects are due to damage to the temporal papillomacula bundle
If true, explain why.
If false, explain what the defect is due to.

Answer 14

False
It is due to damage at the junction of the inferior-temporal quadrants

Question 15

On average, by how many degrees is the ONH higher than the fovea, and how does this affect nerve fibres synpasing from the disc to the fovea (which quadrant specifically)?

Answer 15

On average 5 degrees higher than the fovea
This means nerve fibres synapse from the inferotemporal disc to the fovea

Question 16

What two defects does damage to the inferotemporal quadrant reigon of the disc lead to and in what degree of the visual field?

Answer 16

Leads to superonasal steps and arcuate defects within the central 10 degree visual field

Question 17

If the fovea-disc angle is larger, what is more likely?

Answer 17

Parafoveal VF defects

Question 18

List an advantage and disadvantage of SITA standard for VFs.

Answer 18

Advantage - greater number of thresholding steps - more precise
Disadvantage - longer testing time

Question 19

List an advantage and disadvantage of SITA fast for VFs.

Answer 19

Advantage - quicker testing time
Disadvantage - slightly less precise

Question 20

What do studies comparing SITA standard to SITA fast suggest?

Answer 20

While SITA standard is more precise, it is unlikely to make a difference to improve the time to detect VF progression

Question 21

How much faster is SITA fast vs SITA standard?

Answer 21

50% faster

Question 22

Does SITA fast require a new baseline if switching over from SITA standard?

Answer 22

No

Question 23

Are SITA fast and SITA standard interchangeable?

Answer 23

Yese

Question 24

List four types of defects typical of early glaucoma.

Answer 24

Nasal step
Paracentral scotoma
Arcuate defect
Temporal wedge

Question 25

Are defects more likely to be found in the superior or inferiord hemifield? By how many times?

Answer 25

2-5 times more likely for visual field defects to be located in the superior hemifield

Question 26

What percentage of glaucoma patients in both eyes had defects in only the infeiror hemifield?

Answer 26

Less than 10%

Question 27

Are visual fields subjective or objective? Is it very variable?

Answer 27

Subjective Very variable

Question 28

List three reliability indicators for visual fields and describe them in terms of their effect on reliability.

Answer 28

Fixation losses - may be acceptable False positives - always bad False negatives - least worrisome

Question 29

In what three ways can fixation losses be evaluated? Explain each. Note which is the least effective.

Answer 29

Blind spot monitor -ONH location mapped early -if patient shifts/tilts head, fixation losses are flagged Video monitor -requires practitioner attention -least effective Gaze tracker -relies on a good corneal reflex, doesnt always work

Question 30

Define mean deviation for visual fields. How is it grouped, and what is the measurement range?

Answer 30

Overall depression of visual fields compared to age-matched normals Grouped in decades 0dB to -35dB

Question 31

List three things that can affect mean deviation.

Answer 31

Media opacity Small pupils Uncorrected refractive error

Question 32

Define point standard deviation and what it highlights.

Answer 32

Point variance from the patient's own hill of visiond Highlights areas of scotoma more depressed than the mean deviation

Question 33

What is the visual field index, what data does it use (2), and is it easily comprehended by patients?

Answer 33

A global index that assigns a number between 1% and 100% based on an aggregate percentage of visual, function with 100% being a perfect age-adjusted visual field Uses data from mean deviation and point standard deviation Easily comprehended by patients

Question 34

Is visual field index affected by cataract/media opacities?

Answer 34

No

Question 35

What is a glaucoma hemifield test?

Answer 35

Cluster comparison between superior and inferior hemifields

Question 36

What is the most common grading system for grading the severity of glaucomatous VF defects? What is it based on and what does it represent? What has it recently begun utilising and why?

Answer 36

Glaucoma staging system Based on mean deviation -overall reduction in sensitivity Recently utilises visual field index -to eliminate effect of cataract on progression analysis

Question 37

Describe the three stages of the glaucoma staging system in terms of mean deviation and VFI cutoffs.

Answer 37

Mild -MD 0 to -6dB -VFI 100 to 80% Moderate -MD -6 to -12dB -VFI 80 to 60% Severe -MD worse than -12dB -VFI <60%

Question 38

True or false VF defect within 5 degrees of fixation at any level of mean deviation is considered to be severe glaucoma

Answer 38

True

Question 39

Is it easy or difficult to differentiate random VF losses from true early glaucoma?

Answer 39

Very difficult

Question 40

If a defect is found, what needs to be shown and how long later?

Answer 40

Needs to be repeatable 2-4 weeks later

Question 41

Ideally, how many tests in a row should a defect be present?

Answer 41

3

Question 42

Do significant defects tend to occur in clusers or individual points?

Answer 42

Clusters

Question 43

Is mean deviation good for early detection of glaucoma? Explain why.

Answer 43

Not good Averages all points, missing earlyy shallow defects

Question 44

Is VF testing varialbe from visit to visit?

Answer 44

Yes

Question 45

What is needed for a baseline for VF testing when starting glaucoma assessmentd? Explain why it needs to be so.

Answer 45

Need 2 or 3 VF tests close together to establish a baseline and determine the patients variability in taking the test Needs to be close together so that nay variations are due to the patient's performance, not glaucoma progression

Question 46

What is considered true deterioration for VF (2)? What does assessing this require?

Answer 46

When the change over time is worse than the natural deterioration of VF with age and the patient's own inherent variability Requires guided progression analysis

Question 47

What are two methods of detecting progression using guided progression analysis?

Answer 47

Event analysis Trend analysis

Question 48

What does an event analysis do? What three things does it detect? What is it based on? What does it flag?

Answer 48

Looks for change in each point of the VF -deepening of an existing scotoma -widening of an existing scotoma -new scotoma in a different part of the field It is based on pattern deviation plot, not mean deviation Flags points that have changed more than the patient's inherent variability

Question 49

What is the minimum number of VF exams needed for an event analysis? Describe them.

Answer 49

3 2 baselines, one followup

Question 50

What does event analysis tell us? What does it not tell us?

Answer 50

If progression has occured, not how quickly

Question 51

What does trend analysis look for? What does it use (2)? Is it quicker or slower than event analysis?

Answer 51

Looks for progression over the entirety of the visual field, not each point Uses global data from mean deviation or visual field index Takes longer to statistically detect progression than event analysis

Question 52

What is the minimum number of VF exams needed for a trend analysis?

Answer 52

5 - 6 VF exams

Question 53

What does trend analysis reveal (2) and what does it not tell us?

Answer 53

Reveals occurence of progression and rate of progression Doesnt tell us which part of the VF is worsening (event analysis tells us this)

Question 54

What can trend analysis calculate?

Answer 54

Rate of progression to predict future VF loss -calculates time taken to progress to blindness

Question 55

How is rate of progression measured in trend analysis?

Answer 55

dB/year of MD loss or %/year VFI loss

Question 56

What is the average rate of loss?

Answer 56

-0.06dB/year (virtually no progression)

Question 57

What is considered slow progression? What about rapid? What about catastrophic? What percentage of glaucoma patients fall into each category?

Answer 57

Slow - less than -1.0dB/year (95%) Rapid - more than -1.0dB/year (4.3%) Catastrophic - more than -2.0dB/year (1.5%)

Question 58

Do all patients progress at the same rate?

Answer 58

No

Question 59

What percentage of untreated glaucoma patients did not progress over 5 years, if any?

Answer 59

38%

Question 60

What percentage of untreated normal tension glaucoma patients did not progress over 7 years, if any?

Answer 60

50%

Question 61

How often should VFs be taken for a newly diagnosed glaucoma patient? What does this allow for? Does it matter when they are done? Explain.

Answer 61

6 tests in the first two years Allows for progression rate to be determined Compared with 4 month and 6 monthly VF tests evenly spaced over 2 years, clustered VF testing (3 at t=0, 3 at t=2) is more sensitive with fewer false positives

Question 62

What is the aim when considering the frequency of VF testing?

Answer 62

To find patients progressing more than -1.0dB/year -most likely to progress to blindness

Question 63

Is a rapid VF test done frequently more valuable than a longer, more precise test done infrequently?

Answer 63

Yes

Question 64

What is required for a definitive diagnosis of glaucoma? Explain.

Answer 64

3 structural signs of glaucoma that all match each other No need to have a VF defect for diagnosis