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Ocular Disease II > Glaucoma: Imaging Technology > Flashcards

Glaucoma: Imaging Technology Flashcards

1
Q

Imaging Tech

  1. OCT (tomography); Confocal Scanning Laser Polarimetry (GDx); Scanning Laser Tomography (HRT): What are all of these devices primarily used for in clinic?
  2. These imaging tests have to meet 3 criteria to be useful…?
  3. What precedes VF Loss?
A
  1. to evaluate the RNFL
  2. Differentiate b/w Healthy and Glaucomatous Eyes; Detect progression and Detect Glaucoma changes earlier than functional changes
  3. RNFL Loss
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2
Q

Imaging Tech

  1. Glaucoma is a DISEASE of what?
    a. What is one of the best indicators b/w Healthy and Glaucomatous EYES?
A
  1. ASYMMETRY

a. Symmetry or Asymmetry b/w the 2 eyes.

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3
Q

Imaging Tech

  1. Confocal Scanning Laser Perimetry (GDx)
  2. Scanning Laser Tomography (HRT)
  3. Spectral Domain Optical Coherence Tomography (OCT)
    * What does each one measure?
A
  1. measure’s RNFL
  2. Quantifies Disc Topography
  3. does BOTH!
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4
Q

Imaging Tech: OCT

  1. 2 Main Types: Time-Domain and Spectral-Domain: WHICH has the HIGHER RESOLUTION?
  2. OCT is Great at DETECTING what?
  3. VFs are GREAT at MONITORING what?
A
  1. Spectral-Domain
  2. and Monitoring EARLY GLAUCOMA
  3. ADVANCED GLAUCOMA!
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5
Q

Imaging Tech: OCT

  1. What makes the OCT really Precise?
  2. 3 OCTs we talked about?
A
  1. It computes Tomographic Images based on Amt of Incident light that is reflected for a given tissue.
  2. a. Zeiss Circus
    b. Heidelberg Spectralis
    c. Zeiss Stratus (Time Domain)
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6
Q

Imaging Tech: OCT: Measurement Boundaries

  1. Retina
    a. Inner boundary
    b. Outer Boundary VARIES
    i. Stratus
    ii. Cirrus
    iii. Spectralis
  2. Disc Margins (Automated Identification)
    a. Stratus Reference?
    b. SD-OCT?
A
  1. a. ILM for all
    b. i. PR inner/outer segment interface
    ii. Outer RPE
    iii. Bruch’s
  2. a. RPE/Choriocapillaries +150 um above RPE
    b. BRUCH’s MEMBRANE is reference
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7
Q

Imaging Tech: OCT: Reliability

  1. Stratus
    a. Test/Re-test variability of what?
    b. Be suspicious of changes of what?
  2. Cirrus
    a. Thinning of what?
  3. Spectralis
    a. Clinically appears to have what?
    b. A loss of what amt/yr in progressing pts vs a loss of what/yr in Stable patients?
  4. Repeatability Factors
    a. Signal Strength > or equal to what?
    b. Dilation: effect?
A
  1. a. 4-10 um per quadrants
    b. >10um
  2. a. of 4-6 um b/w visits is suspicious
  3. a. Very low fluctuation
    b. 2.12 um/yr in progressing pts vs. loss of 1.18 um/ys in stable pts
  4. a. 7
    b. may not have an effect on repeatability
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8
Q

Imaging Tech: OCT: Normative Databases: STRATUS

  1. Split pretty evenly b/w Males and Females
    a. Mean Age?

b. Rx?
c. % Caucasian?
d. What other things?

A
  1. a. 47.4 +/- 15 yrs
    b. -11.75 to +6.75
    c. 63%
    d. No eye surgery except cataracts (9 pts), No ocular disease, IOP < 22mmHg, normal and reliable VF, Normal ONH, BBCVA >20.32
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9
Q

Imaging Tech: OCT: Normative Databases:
Cirrus

  1. Age Range
  2. Rx?
  3. % Caucasians?
A
  1. 19-84
  2. -12 to +8
  3. 43%
    * All normal subjects
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10
Q

Imaging Tech: OCT: Normative Databases:
Spectralis

  1. % Male
  2. Age
  3. Rx?
  4. % White?
  5. What other things
A
  1. 55%
  2. 48.2 +/-14.5 yrs
  3. -7 to +5
  4. 100%
  5. No glaucoma, Normal IOP, normal VF, normal Optic Nerve
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11
Q

OCT: Avg Thickness

  1. Stratus
  2. Cirrus
  3. Spectralis
A
  1. 99-100 um in whites/Japanese and Up to 132.7 um in Hispanics
  2. Avg 94 um
  3. Avg 102 um
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12
Q

OCT: Diagnosing Glaucoma

  1. TD (something domain) and SD (Spectral Domain) have what for detecting glaucoma?
  2. Diagnostic Criteria?
A
  1. High Sensitivity and High Specificity

2. More than 1 clock hour at <0.01 Level (Red)

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13
Q

OCT: Detecting Progression

  1. Considerations
    a. Is there a consensus on the limit of RNFL thinning that equals Progression?
    b. Avg RNFL thickness may be better than what?
A
  1. a. NO!
    b. than the Sectoral Analysis with LOWER Inter-Test VARIATION!
  • event Based Analysis: Specific AREAS of the VF is looked at
  • Trend Based Analysis: Rate of Progression overall
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14
Q

OCT: Detecting Progression

  1. Age-Related RNFL Loss
    a. Avg Rate?
    b. Significant change in Nasal and Temporal Quadrants w/Age?
    c. Rates b/w Normal and Glaucoma Patients Vary?
A
  1. a. -0.10 to -0.52 um/year
    b. NO significant Change
    c. -0.17 to -0.86 um/year is CONSIDERED NORMAL

> 2.54 um/year is SIGNIFICANT (outside 95% CI)

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15
Q

OCT: Reading the Printout

  1. RNFL Peripapillary Thickness PRofile OU:
  2. Neuro-Retinal Rim Thickness Profile OU
  3. RNFL Quadrant and Clock Hour Avg Thickness (OD and OS)
  4. Asymmetry OD-OS
A
  1. Matched to Normative Data
  2. same
  3. same as above
  4. Intra-Eye Comparison
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16
Q

Recent OCT Developments

  1. Ganglion Cell Complex (GCC)
    a. Measures thickness for the sum of what 2 Layers?
    b. RNFL distribution in the Macula depends on what?
    c. GCL + IPL appear to be Regular and Elliptical for whom?

d. There is some evidence that changes in the GCC may precede changes in what?
2. Consider what OCTs for Glaucoma patients?

A
  1. a. GCL + IPL
    b. on Individual anatomy
    c. for Most normals…so deviations from normal are more easily appreciated in the thickness map, and Arcuate Defects seen in the deviation map may be less likely to be due to anatomical variations.
    d. in the RNFL
  2. Both RNFL OCT and Macular OCT!
17
Q

OCT: EDI-OCT (Enhanced Depth Imaging)

  1. New imaging Technique. Allows for better imaging of what?
    a. What 2 OCTs use this currently?
  2. It does have Glaucoma Diagnosis Implications: POSTERIOR DEFORMATION of the ANTERIOR LAMINAR CRIBROSA SURFACE (ALCS) preceded or was Concurrent with changes in what?
    a. Laminar Pores initially became more what shape before becoming what?
    b. EDI-OCT may allow us to EXAMINE LAMINA CRIBROSA Morphology and diagnose glaucoma when?
A
  1. of the CHOROID!
    a. Spectralis OCT (Heidelberg), and Cirrus HD OCT
  2. in PORE GEOMETRY and RNFL THICKNESS in EARLY GLAUCOMATOUS EYES (experimental Glaucoma)
    a. More OVAL before becoming more ELONGATED in early glaucoma
    b. Even earlier than with RNFL and GCC
18
Q

GDx: How it basically works (First technology to measure RNFL!)

  1. Laser double passes the RNFL and is split into 2 what?
    a. Laser light enters eye at a specific orientation. As it goes thru Tubules (ganglion cells), it returns at what?
    b. The delay in return (Retardation) is how we measure what?
A
  1. 2 parallel rays by the birefringent fibers (this is kind of important…because Anterior segment of the eye also has birefringent properties as well…so DO NOT touch cornea before TAKING THIS…so TAKE this SCAN PRIOR to IOP and no DILATION!)
    a. at a different orientation/axis
    b. the thickness. Parallel light passes thru at a different speed than perpendicular light
19
Q

GDx (2)

  1. Measurement time?
  2. Total chair time for both eyes is less than what?
  3. IT’s completely what?
  4. Must have Clear CORNEAL SURFACE with GOOD TEAR LAYER: so…Do…?
  5. What pupils work best?
A
  1. 0.7 seconds
  2. Less than 3 minutes
  3. Objective
  4. DO NOTHING to the CORNEA before this TEST
  5. Undilated pupils are BEST
20
Q

GDx (3)

  1. Corneal Compensation
    a. What does it MEASURE?
    b. To an extent, what also has Birefringent properties?
    c. This introduces what into the scan?
  2. What is the Propiretary method to remove residual artifacts from scans?
  3. FOR NEW PATIENTS, what must be completed FIRST?
    a. Is this done on subsequent scans?
A
  1. a. Birefringence of the NFL
    b. Cornea (as well as the lens)
    c. Artifacts (so…not everything measured by the GDx is NFL)
  2. Enhanced Corneal Compensation (GDxPro): Proprietary method to remove residual artifacts from scans
  3. a MACULAR SCAN (Macular should have NO BIREFRINGENCE due to anatomy of NFL)…If you see a BOWTIE APPEARANCE retarding the Image then the artifact showing thru is from the Anterior Segment (Cornea)
    * Puprpose of Macular Scan: To adjust for corneal-induced Artifact
    b. No…uses stored data; Only need to do a Macular scan again if there’s been a SIGNIFICANT change in the CORNEA (corneal Transplant, refractive Surgery)
21
Q

GDx: VCC: Printout

  1. TSNIT Standard Deviation
  2. Inter-Eye Symmetry
  3. Nerve-Fiber Indicator/Integrity (NFI)
    a. What is it?
    b. 0-30 = ?
    c. 31-50 = ?
    d. 51-100 = ?
    e. *NOT AN INDICATION of SEVERITY or PROGRESSION, but only tells you if what is present?
A
  1. of values contained in the calculation circle. HIGHER NUMBER = GREATER MODULATION of the DOUBLE HUMP PATTERN (that is, the Higher the Superior and Inferior Peaks)
  2. Correlation of Corresponding points in TSNIT data for right and left eyes. RAtio CLOSER to 1.0 = MORE SYMMETRIC NFL
  3. a. Single number meant to indicate whether or not the patient has glaucoma
    b. Normal (low change of Glaucoma)
    c. Glaucoma suspect
    d. High likelihood of glaucoma!
    e. only tells us if an ABNORMAL NFL is there.
22
Q

HRT

  1. What does is measure?
  2. Best machine capable of detecting what?
    a. Drawback?
  3. VERY SENSITIVE in what?
  4. Source of Error
A
  1. Objective measurement of Optic Nerve and Surrounding Topography
  2. Glaucoma changes over time.
    a. You have to PHYSICALLY DRAW the DISC MARGIN (greatest source for error!)
    * Once you draw it, you don’t have to do it again. (don’t want to or you won’t get consistent data over time)
  3. In DETECTING CHANGE OVER TIME
  4. Operator uses image to subjectively plot the Contour Line (Edge of the DISC)
23
Q

HRT: Clinical Use

  1. 2 Main sources of error w/this technology?
    a. Since these can be incorrect, this makes the HRT not a good what?
    b. However, in sequential analyses, these sources of error REMAIN how?
  2. Image: Bright colors represent what?
    a. Red = ?

b. Dark colors = ?
c. Blue = ?
d. Green = ?

A
  1. Contour Line (subjective determination of edge of the disc) and reference plane set by the device to delineate the cup rim.
    a. It’s not a good on-the-spot diagnostic device
    b. remain CONSTANT and the DEVICE is GOOD to measure change over time.
  2. Depth
    a. Cup

b. Elevation
c. Sloping
d. Neuroretinal Rim

24
Q

HRT: Differences in F/U Report

  1. Beginning w/which F/U Exam?
  2. Regions with significant changes are color coded
    a. Red = ?
    b. Green = ?

c. Why is topography F/U Black and White?

A
  1. 2nd F/u exam
  2. a. Decreased Height
    b. Increased Height

c. for better contrast

Ocular Disease II (15 decks)

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