DIS - Glaucoma Assessment Tutorial II - Week 5 Flashcards
What is better at discriminating glaucoma suspects from glaucoma patients, OCT or stero photos?
OCT
Is it common or rare to find simultaneous defects in both structures and function at diagnosis?
Rare
What is the issue of correpating structure and function of the ganglion cells? Describe in terms of VF sensitivity.
The variability in ganglion cell density as we move away from the fovea
How much does a 3dB point reduction in VF sensitivity correlate with the number of ganglion cells outside the macula and the perifovea?
10 ganglion cells outside the macula
230 ganglion cells in the perifovea
Once a field defect is present, is progression better detected by VF changes or disc changes?
VF changes
Comparing structure vs function (VF), which is better at detecting early glaucoma? what about more advanced glaucoma?
Structure better at detecting early glaucoma
VFs better for advanced glaucoma
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)?
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
How many test points does the 30-2 have? Give one advantage and two disadvantages.
76
Advantage - more points in the temporal field
Disadvantage - longer test time, variable threshold of outer ring of points
How many test points does the 24-2 have? Give three advantages.
54 Advantages -still tests out to 30 degrees in the nasal step region -quicker test time minimises outer ring variability
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?
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
What does the evidence comparing 30-2 and 24-2 suggest in terms of best compromise for speed, comfort, and reliable data?
24-2 in most cases gives the best compromise while being comparable to 30-2
Consider the visual field area tested by 10-2. What quadrants are affected first in glaucoma (2)?
Inferotemporal and superotemporal
When is the temporal disc often affected in glaucoma? What about the nasal quadrant of the disc?
Not until later in the disease
The nasal quadrant is last
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.
False
It is due to damage at the junction of the inferior-temporal quadrants
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)?
On average 5 degrees higher than the fovea
This means nerve fibres synapse from the inferotemporal disc to the fovea
What two defects does damage to the inferotemporal quadrant reigon of the disc lead to and in what degree of the visual field?
Leads to superonasal steps and arcuate defects within the central 10 degree visual field
If the fovea-disc angle is larger, what is more likely?
Parafoveal VF defects
List an advantage and disadvantage of SITA standard for VFs.
Advantage - greater number of thresholding steps - more precise
Disadvantage - longer testing time
List an advantage and disadvantage of SITA fast for VFs.
Advantage - quicker testing time
Disadvantage - slightly less precise
What do studies comparing SITA standard to SITA fast suggest?
While SITA standard is more precise, it is unlikely to make a difference to improve the time to detect VF progression
How much faster is SITA fast vs SITA standard?
50% faster
Does SITA fast require a new baseline if switching over from SITA standard?
No
Are SITA fast and SITA standard interchangeable?
Yese
List four types of defects typical of early glaucoma.
Nasal step
Paracentral scotoma
Arcuate defect
Temporal wedge
Are defects more likely to be found in the superior or inferiord hemifield? By how many times?
2-5 times more likely for visual field defects to be located in the superior hemifield