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III. Glaucoma Management > NFL and Glaucoma Imaging Devices (M) > Flashcards

NFL and Glaucoma Imaging Devices (M) Flashcards

1
Q

What kind of OCT shift is seen in malinserted discs?

A

temporal axis shift (both shift out on TSNIT)

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2
Q

What are the important factors about the Stratus OCT compared to Cirrus?

A
  1. less resolution
  2. falsely thicker NFL (7-10 microns)
  3. less sensitive
  4. higher false negatives
  5. less reproducible
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3
Q

When the NFL is almost completely gone, why does the NFL thickness still have a measurement?

A

Not just measuring GC axons but also support structures (glial cells and BVs)

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4
Q

What should NFL findings be correlated with?

A
  1. findings in optic nerve evaluation in exam

2. VF

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5
Q

What are the clinical examples of how an OCT can create a false positive or “red disease”?

A
  1. poor image acquisition
  2. PPA/crescents
  3. malinserted discs
  4. tilted discs
  5. comparing Stratus OCT to Cirrus OCT
  6. disc drusen
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6
Q

What retinal findings can lead to higher false negatives?

A
  1. retinal edema
  2. myelinated nerve fiber layer
  3. epiretinal membrane
  4. disc drusen (can also be false positive)
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7
Q

What leads to measurement errors for HRT?

A
  1. only estimates NFL thickness
  2. large and small ONH that falls outside normative database
  3. high refractive errors
  4. contour line plotting inaccuracy
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8
Q

What is the best detection/progression analysis method for early glaucoma?

A

OCT

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9
Q

What is the best progression analysis method for advanced glaucoma?

A

visual field because NFL done and won’t get any thinner

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10
Q

What are thick NFL values colored in the thickness map of a GDx?

A

yellow, orange or red

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11
Q

What are considered significant changes on repeat testing for the average NFL thickness? 1. Quadrant NFL thickness? 2. Sector NFL thickness? 3

A
  1. 5 microns
  2. 10 microns
  3. 10 to 15 microns
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12
Q

What is the resolution of the Stratus OCT? 1. Cirrus OCT? 2

A
  1. 10 microns

2. 5 microns (better)

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13
Q

What are the benefits of NFL measurement?

A
  1. objective measurement

2. quantifiable NFL data for comparison to normal and progression

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14
Q

What is the analysis of HRT that uses the ethnic background of a patient and identifies patterns of structural change consistent with glaucoma?

A

HRT 3 Glaucoma Probability Score (GPS)

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15
Q

What does the signal strength of an OCT measure? 1. What is the range of scores? 2. What are acceptable scores? 3. What can cause low scores? 4

A
  1. assessment of how clear the image was and how many scans processed
  2. 1 to 10
  3. greater than 6
  4. artifacts from cataracts, guttata, corneal edema, ptosis from dermatochalasis
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16
Q

What are the important aspects of a GDx printout?

A
  1. Q value
  2. ONH photo
  3. Thickness map
  4. deviation plot
  5. TSNIT graph
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17
Q

What is the most important anatomical factors while looking at the retina to determine glaucoma presence in order from most to less important?

A
  1. rim area
  2. inferior-temporal (5-7 o’clock) sector loss
  3. inferior quadrant
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18
Q

What made up the Cirrus normative database?

A

284 subjects from 19-84 with refractive error of +8 to -12 and of different heritage

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19
Q

What is the algorithm used for interpretation of results when comparing normal to glaucomatous retinas for HRT?

A

Moorfields Regression Analysis (MRA)

20
Q

What is the sensitivity for detection of a GDx when there is no VF loss but is ONH changes? 1. Specificity? 2. Sensitivity with VF loss? 3. Specificity? 4

A
  1. 83%
  2. 82%
  3. 89%
  4. 96%
21
Q

What must the Q value be to use the GDx?

A

7 or greater

22
Q

What is the term to explain the phenomenon of classifying a patient as abnormal just because the statistical analysis shows red?

A

Red disease (false positives)

23
Q

What is the imaging device that analyzes both the ONH and NFL? 1. Just the NFL? 2. Just the ONH and NFL extrapolation? 3

A
  1. OCT
  2. GDx (scanning laser polarimetry)
  3. HRT (scanning laser ophthalmoscopy)
24
Q

What kind of OCT shift is seen in tilted discs? 1. Where does this create anomalies? 2

A
  1. peaks shift in same direction on TSNIT

2. quadrant an sector analysis

25
Q

What percentage of people fall within the white band of the normal database (and what does this mean)? 1. Green band (meaning)? 2. Yellow band (meaning)? 3. Red band (meaning)? 4

A
  1. 5% (outside normal limits, thicker)
  2. 90% (good)
  3. 4% (caution)
  4. 1% (outside normal limits, thinner, danger)
26
Q

What are the aspects that need to analyzed from an OCT about the image quality?

A
  1. well centered optic nerve
  2. no degree of black on NFL
  3. reflectance map = color is good (thicker in sup and inf making hour glass)
  4. deviation map = color is bad
27
Q

What type of filter allow you to possibly see some losses in the NFL through basic examination?

A

neutral density filter

28
Q

What imaging principles are used for HRT?

A

reflectance

29
Q

What are the strengths of HRT?

A
  1. ability to detect change from normal to glaucoma or progression of glaucoma
  2. more accurate when there is a PPA, oblique insertions and tilted nerves
30
Q

How many exams must take place in order to run a Guided Progression Analysis (GPA)? 1. What is used as the baseline? 2

A
  1. 3

2. average of first two OCT measurements

31
Q

What imaging principles are used for GDx? 1. What causes errors with this? 2

A
  1. birefringence of scanning laser polarimetry

2. cornea (but VCC and ECC helps in new models)

32
Q

What do no squares for a deviation map of a GDx indicate? 1. Dark blue squares? 2. Light blue? 3. Yellow? 4. Red? 5

A
  1. normal
  2. only 5% probability NFL within normal limits
  3. 2% probability
  4. 1% probability
  5. 0.5% probability
33
Q

What is the amount of sensitivity of the RNFL average thickness for the Cirrus OCT? 1. Specificity? 2

A
  1. 83%

2. 88%

34
Q

What are the steps to interpret an OCT?

A
  1. signal strength
  2. image quality
  3. look at key ONH parameters
  4. statistical analysis compared to normative database
  5. rule out artifacts
  6. correlate with ONH appearance and VF
  7. Compare to previous OCT measurements and/or GPA
35
Q

How many exams can be compared in the serial analysis of GDx?

A

4

36
Q

What are the ocular structures that have the highest reflectivity (red)? 1. Intermediate reflectivity (yellow)? 2. Low reflectivity (green)? 3. No reflectivity (black)? 4

A
  1. NFL, RPE, choriocapillaris
  2. inner and outer plexiform layers
  3. inner and outer nuclear layers
  4. vitreous, photoreceptor, intraretinal cysts, blood
37
Q

What analyzes the entire NFL profile from normative database and provides a single number representing the integrity of entire NFL for a GDx? 1. What is normal? 2. Glaucoma suspect? 3. High likelihood of glaucoma? 4

A
  1. Nerve Fiber Indicator (NFI) for ECC
  2. less than 35
  3. 35 to 55
  4. above 55
38
Q

What is the OCT image created from that is different for different tissues of the eye?

A

reflectivity

39
Q

How is the reflectance image topography of the HRT printout displayed?

A

divided into 6 quadrants compared to norms with green checks, yellow !, or red X

40
Q

What are the limitations of NFL measurement?

A
  1. not 100% sensitive (false negatives)
  2. no 100% specific (false positives)
  3. interpretation errors
41
Q

What imaging tool measures the optic nerve cup and rim and estimates an indirect calculation of NFL thickness?

A

HRT

42
Q

Do changes in the NFL show up earlier or later than changes in the cup?

A

earlier

43
Q

When looking at the topography of the ONH with a HRT what does the red indicate? 1. Blue? 2. Green? 3

A
  1. cup
  2. sloping portion of the rim
  3. true rim defined by equal to retinal surface height
44
Q

What is a total disc area that is considered small? 1. Large? 2

A
  1. less than 1.58mm2

2. more than 1.88mm2

45
Q

What scans does the “Optic Disc Cube 200x200” perform? 1. What does it provide? 2

A
  1. 200 A-scans and 200 B-scans in 6x6mm area

2. RNFL measurement, ONH analysis, ganglion cell complex all compared to normative database

46
Q

What is the range of normal rim area in mm2?

A

1.03 to 1.69

III. Glaucoma Management (9 decks)

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