DIS - Ocular Imaging III - Week 8 Flashcards

1
Q

What are 5 methods available to image glaucoma?

A

Drawing
Photography
Scanning laser tomography
Scanning laser polarimetry
Optical coherence tomography

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2
Q

How does a scanning laser tomographer work and how can the focal plane be changed?

A

A low power laser is scanned in raster fashion over the retina, reflected light is descanned and detected by a photodiode
A small pinhole placed in front of the photodiode can be moved to select the focal plane

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3
Q

How does a scanning laser polarimeter work?

A

Measures the phase shift of polarised light passing through the eye
-retardation is affected by the arrangement and density of the RNFL

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4
Q

What is variable corneal compensation used for (2) and for what imaging technique?

A

Used in scanning laser polarimetry
-determines and corrects for each patient’s individual non-RNFL retardation

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5
Q

List 6 analysis results available for the RNFL with scanning laser polarimetry.

A

Fundus image
RNFL map
Deviation map
TSNIT graph
Parameters/indices

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6
Q

List the two types of OCT available and which is theoretically better and why (2). Compare the diagnostic accuracy of the two.

A

Time domain
Spectral domain - theoretically better
-spectral domain has high resolution and faster scanning - higher reproducability
Diagnostic accuracy of the two are similar

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7
Q

Which is faster, spectral domain or time domain?

A

Spectral domain

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8
Q

Can spectral domain give 3D image patterns?

A

Yes

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9
Q

Where is the loss of cells more easily detected and why?

A

At the macula because it has the highest concentration of RGCs

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10
Q

What is the minimum distance band and is it better than RNFL thickness in distinguishing glaucomatous eyes from healthy eyes? What technique is it used in?

A

Spectral domain
Shortest distance between the ILM and bruch’s membrane/RPE termination
MDB is better than RNFL thickness

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11
Q

List three 3D rim parameters and 2D rim parameters each. Which is better?

A

3D
-minimum distance band
-minimum rim width
-rim volume
2D
-RNFL thickness
-rim area
-rim thickness

3D rim parameters generally outperform 2D

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12
Q

Compare total macular thickness to RNFL thickness for glaucoma diagnosis.

A

Total macular thickness is worse

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13
Q

List three segmentation macular parameters and their performance (2).

A

Macular RNFL (mRNFL)
Ganglion cell and inner plexiform layer (GCIPL)
Ganglion cell complex (GCC) - GCC = mRNFL + GCIPL
GCIPL is similar to RNFL and ONH
Minimum GCIPL is the most sensitive parameter

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14
Q

What is an issue with most glaucoma detection studies for diagnosing early glaucoma?

A

Most detection studies look at discrimination between healthy eyes and established glaucoma
-may not translate to early glaucoma

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15
Q

Which of the following is significantly better than the others for pre-perimetric glaucoma:
RNFL
ONH
Macula

A

RNFL

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16
Q

Is myopia a risk factor for glaucoma?

17
Q

Do structural changes in myopia mimic glaucoma?

18
Q

What are thick artefacts seen with myopia due to?

A

Refractive error and eye length

19
Q

Can non-glaucomatous eyes be classified as abnormal?

20
Q

Compare the macula and RNFL thickness’ ability to detect glaucoma in myopic eyes.

A

They are similar

21
Q

Is RNFL thickness diagnostically accurate for detecting glaucoma?

22
Q

Compare segmented macular and ONH parameters to RNFL

A

Comparable, perhaps better

23
Q

Are there differences in absolute measurements between instruments? Do different instruments have similar diagnostic abilities?

A

There are differences in absolute measurement
Different instruments have similar diagnostic abilities

24
Q

Explain the sensitivity and specificity capability of OCT and comment if it is good enough for population screening glaucoma.

A

They are not high enough to be cost-effective for population screening

25
What is essential for glaucoma after it is diagnosed and why?
Detecting progression because it will guide treatment
26
What does progression detection require (3)?
Discrimination between: -glaucomatous structural damage -measurement variability -age related structural loss
27
Which is more sensitive to RNFL changes, spectral domain or time domain?
Spectral domain
28
What is compared in event-based progression analysis and when is progression indicated? List one advantage and disadvantage.
Compares a follow-up measurement to a baseline measurement Advantage - few tests required Disadvantage - susceptible to outliers
29
What is compared in event-based progression analysis and when is progression indicated? List two advantages and disadvantages.
Looks at the slope/rate of a line fit through the parameter over time Progression is indicated when the slope exceeds a threshold Advantages -less sensitive to measurement variability -rate can be used to make a time-to-event prediction Disadvantages -large number of tests needed before analysis is reliable -assumes linear loss
30
Compare the sensitivity of RNFL, TMT, and GCIPL in detecting glaucoma progression.
All similar
31
Compare the loss of TMT and RNFL in glaucoma progression groups to stable and undetermined groups.
Rate of TMT loss was greater in glaucoma progression Rate of RNFL loss was similar
32
What wavelength does swept-source OCT use and list two advantages of this.
Longer wavelength -deeper penetration -faster scan rate
33
Compare the sensitivity of swept-source OCT for diagnosing pre-perimetric and early glaucoma.
May be more sensitive
34
What does adaptive optics OCT allow identification of?
Width of nerve fibre bundles