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Glaucoma > Lecture 9: VF/Function Specific Perimetry > Flashcards

Lecture 9: VF/Function Specific Perimetry Flashcards

1
Q

____ is the central detection and monitoring of visual function in glc

A

Perimetry

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2
Q

Physiological blind spot is about __ degrees temporal from fixation

A

15

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3
Q

What is the hill of vision?

A
  • Optic Disc Imaging, RNFL Analysis and Ganglion Cell Analysis
  • Axons of the optic nerve fibers are contained in the RNFL
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4
Q

___ is the clincal standard for measuring glaucomatous VF defects

A

Standard Automated Perimetry (SAP)

  • Clinical standard for measuring glc VF defects
  • Glaucomatous loss detected/managed more reliably compared to manual perimetry
  • Uses static perimetry
  • Threshold sensitivity presented in decibels (dB)
    • 0 dB = bright intensity
    • Values of 30 dB are normal values
    • Value are relative and not directly comparable across different makes of perimeters
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5
Q

What is suprathreshold technique

A
  • Relatively quick to administer
  • Record whether a location is normal (stimulus seen) or abnormal (not seen)
  • Uses a stimulus 4-6dB brighter than expected threshold
    • Chooses from age-matched database
    • follows expected hill of vision
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6
Q

What is the best technique for glaucoma evaluation? What’s the con of using this test?

A

Full threshold.. IT TAKES SO LONG to do

  • uses 4-2 staircase method
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7
Q

What are the 2 types of full threshold technique? What is the difference between each test?

A
  • Fastpac
    • Reduces test time at the expense of measurement accuracy
  • SITA
    • Reduces test time while maintaining standard of accuracy used in 4-2 threshold testing
    • Takes about 7 mins per eye
    • 2 types: SITA standard & SITA fast
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8
Q
A
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9
Q

SITA standard is designed for

A
  • Designed for glc - do not use it with other conditions
  • Interchanging SITA with conventional full-threshold is not recommended in longitudinal follow up of patients
  • SITA is becoming new gold standard for threshold perimetry in glaucoma
  • Quicker test is naturally appealing
  • Sound research suggests measurement from SITA are in close agreement with full threshold
    • SITA defects do appear shallower
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10
Q

SITA FAST is good in subjects who..

A

have difficulty completeting a long VF test

  • Uses larger step sizes
  • Makes it even qucker in time
  • NOT a great choice for f/u care
    • really only use clincailly if pt have difficulty physically/mentally performing standard test
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11
Q

List 5 Patient dependent factors.

What are the other factors? (5)

A
  • Fatigue effect - difficult to control
  • Inattentiveness - false negative
  • Trigger happy - false positives
  • Fixation loss
  • Learning Curve

Other factors

  • Refractive error
  • Trial lens artifact
  • Pupil size
  • droopy eyelids
  • Media opacities/tear film irregularities
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12
Q

Field loss (SAP) is an indicated for what?

A

advanced disease

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13
Q

If early in disease what test would you order & how often would you repeat testing?

A
  • Baseline 24-2 HVF, consider baseline 10-2
  • Repeat at least every 6 months
  • Follow the ONH and OCT closely for change
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14
Q

If late in disease what test would you order & how often would you repeating testing?

A
  • Follow the 24-2 VF closely for change
  • Repeat at least every 3 months
  • May need to follow 10-2 closely as well
  • Continue to monitor ONH and OCT
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15
Q

What are the common glaucomatous VF defects?

A
  • Arcuate
  • Nasal step
  • Paracentral
  • Diffuse?
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16
Q

T/F a normal VF does not exclude glaucoma

A

TRUE, but it does exclude advanced disease

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17
Q

Approximately __ of RGC lost before 5-10DB of VF reduction

A

40%

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18
Q

fibers from the ___ retina usually most susceptible to damage

A

temporal

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19
Q

Damaged NFL typically give isolated damage in the ___ areas (__ - __ degrees). Eventually forming ____.

A

paracentral; 10-20

Arcuate scotomas

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20
Q

Early non-specific changes produces what type of visual field loss?

A

generalized constriction

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21
Q

Early significant changes produces what type of visual field loss

A
  • Peripheral nasal step
  • Small wing shaped paracentral scotoma
    • Within Bjerrum’s area
    • Isolated or associated with nasal step
  • Siedel’s sickle-shaped scotoma
    • Paracentral scotoma
    • Joins blind spot
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22
Q

What does the image represent? Describe each.

A
  • Schematic showing worsening patterns of VF loss in open-angle glaucoma
  • A. Location of testing points of 24-2, Humphrey VF
  • B. Isolated defects in paracentral area
  • C. Small isolated defects combin to form a larger defect
  • D,E. Arcuate defect forms and worsens and eventually breaks through to the periphery
  • F. End-stage defect, with only small functoinal macular area remaining
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23
Q

What type of VF loss does this represent?

A

Paracentral scotoma

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24
Q

What type of VF loss does this represent?

A

Arcuate scotoma (Bjerrum)

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25
Q

What type of VF loss does this represent?

A

Nasal Step

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26
Q

Quantification procedures applied to VF results can be put into what 3 main categories?

A
  • Analysis of patient response/validity
  • Single field analysis
  • Series of Visual Field Results (Analysis of Progression)
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27
Q

Various confounding elements may cause misinterpretation of VF results. These confounds can include (6)

A
  • Ptosis
  • Patient fatigue
  • Small pupils
  • Poor alignment
  • Trial lens holder artifact
  • Co-morbidities creating compound patterns
    • e.g. glaucoma ptient with h.o retinal vascular occlusions, optic neuropathies, ARMD, diabetic reninopathy, retinal scarring, strokes
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28
Q

Studies have suggested what 2 things to get a good baseline VF?

A
  • at least 2 field taken about 2 weeeks apart necessary
  • If the fields do not show similar results, a third VF taken several months later is useful
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29
Q

What does this image represent? Describe what it is.

A
  • High false positive results produce a “superfield”
  • a.k.a “trigger happy” or rambo”
  • White areas represent higher than normal decibles on the gray scale
  • Characteristic falsely elevated threshold measurements
  • Many probability symbols in the pattern deviation map with a normal total deviation map
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30
Q

What is the importance of gaze tracking?

A
  • Record eye movement monitored during test
  • also records number of times an eye’s position cannot be determined
  • Can only be evaluated subjectively
  • Useful for evaluating quality of fixation, particularly when VF defects surround blind spot
31
Q

What does an upward bar in the gaze tracking chart indicate?

What does the length of the bar indicate?

A
  • upward bar indicates fixation disparity
  • the length of the bar represents manitude of disparity from 1 degree to a max of 10 degree
32
Q

What does a short downard bar represent in gaze tracking?

A

tracking failure

33
Q

What does a long downard bar indicate?

A

indicates eyelid closure

34
Q

Label the following image

A
  • A. Humphrey field analyzer output showing a single field analysis of results form a glaucomatous patient using the SITA standard program
  • B. Reliability indices and test duration is shown in the top of left-hand corner
  • C. The results for GHT
  • D. global indices are shown below the main gray scale
  • E. The total deviation plot
  • F. The pattern Deviation plot
  • Fixation/Gaze Tracking (bottom image)
35
Q

What is a single field analysis?

A
  • analysis based a single VF
  • compares VF with result from normal population or within eye comparisons
  • Block symbols represent different levels of probability with which the particular value would occur in a normal population
    • E.g. black symbol: likelihood of a normal subject having that level of vision is <0.5%
    • Must be regarded as highly suspect
36
Q

Fixation losses must be < __ in order to be reliable

A
  • 20% (will be affected by advaned glaucoma or large blind spots
37
Q

False positive or false negative must be < __-__% in order for VF to be reliable

A

20-30%

38
Q

What is the greyscale on the VF used for?

A

useful for detecting artifacts, overall regions affected and patterns. Also useful for pt education

39
Q

What is total deviation plot?

A
  • difference (in dB) between test results and normative data for the patient’s age group. shows probability of each point being normal
40
Q

What is pattern deviation plot?

A
  • Overall sensitivity changes in the hill of vision. Subtracts overall depression value from each test point. Shows localized defects
41
Q

What is mean deviation?

A

overal dpression of field. should not exceed -2dB

42
Q

What is pattern standard deviation (PSD)? What can cause a high PSD?

A
  • Degree of departure from normal hill of vision. High PSD may be due to low reliability or VF defect or BOTH!
43
Q

What is glaucoma hemifield analysis?

A
  • compare scorresponding point values across the horizontal (upper and lower halves of field)
44
Q

What is glaucoma hemifield test?

A
  • devised to detect field loss that is asymmetric across the HORIZONTAL meridian - characteristic of glaucomatous loss
45
Q

Increased variability may be an ealry sign of …?

A

glaucomatous damage

46
Q

Hart & Becker proposed that glaucomatous VF go through 3 phases

A
  1. Occult: Initial stage with no defect demonstrable despite the fact that occult damage is occurring
  2. Threshold: period in which shallow defects are often transient and are barely detectable
  3. Critical phase: VF defects are detectable and progress at an uneven pace to become dense
47
Q

IN all cases, msut determine whether VF changes are due to what 3 things?

A
  • Noise
  • Neuronal damage
  • Spurious change due to learning & fatigue
48
Q

In clinical practice, VF progression is often determined by combination of what 3 things?

A
  • Clinical judgement
  • Experience
  • Progression analysis software
    • OLDER VERSIONS:
      • Mean Deviation Index plotted against time/Glaucoma change probability (GPC)
    • NEW VERSIONS:
      • Event-based analysis: GPA
      • Trend based analysis: VFI
49
Q

What is global indices used for? What is the drawback?

A
  • Using mean deviation
  • Provides very specifci method for determining change
    • if pt shows change in global indices (MD) (PSD), they most certainly have progression
  • Drawback: insensitive to early localized change
50
Q

What is glaucoma progression analysis used for? (GPA)

A
  • Pointwise method
  • GPA designed to evaluate change in sensitivity from baseline data
    • 2/3 initial fields are merged to give a baseline field
    • The change from baseline is displayed at each test location
      • Data given in symbols
51
Q

What is visual field index? (VFI)

A
  • Most recent version of HFA also provides the VFI and VFI progression plot
  • VFI is relatively new index that is proposed to better evaluate the rate of progression with SAP
  • The aim of this analysis is mainly to provide valuable info on the rate of deterioration of the overall VF
52
Q

VFI is calculated as… ?

A

as the percentage of normal VF, after adjustment for age

  • VFI of 100% represents a completely normal VF
  • VFI of 0% represents a perimetrically blind VF
  • The VFI is shown on the GPA printout both as a percentage value for each individual exam and as a trend analysis, plotted against age
53
Q

What are 3 pros of octopus perimeter?

A
  • Full threshold exam takes less than 2:30 minutes
  • 100% eye fixation control if fixation is lost, no stimulus is presented
  • Diagnostic programs with test stages prioritize the most crucial field areas
54
Q

Who makes a good candidate for octopus perimeter? (4)

A
  • h/o poor reliability on HVF
  • Inability to sit for duration of HVF
  • Equivocal results on previous HVFs
  • Glaucoma suspects with clean fields but reason to believe they actually have glaucoma (e.g. poor OCTs, glaucomatous nerves)
55
Q

What is octopus cluster analysis?

A
  • Designed specifically for glc
  • Very sensitive to detection of subtle glaucomatous defects
  • VF locations corresponding to same RNFL bundle are grouped and used to calculate a mean cluster defect (cluster MD)
56
Q

What is Octopus Polar Analysis?

A
  • Projects local VF defects along the nerve fibers to the optic disk and displays them oriented as structural results
  • Local defects are projected along the nerve fibers to the optic disc and are represented as red lines
57
Q

What is octopus defect curve?

A
  • A graphical representation that alerts the clinician to the presence of diffused defects
  • Provides a summary of VF and makes it possible to distinguish between local and diffuse defects at a glance
58
Q

___ remains the most commonly performed method of VF assessment in glc

A

SAP

  • However, studies have shown that in many cases VF defects on SAP are detectable only when a substantial number of RGCs have been lost
59
Q

Why is there such relative insensitivity of SAP to early RGC damage?

A
  • There is considerable redundancy in teh system
  • Light detection can be perceived by all RGC types
  • BUT certain features are encoded by certain subsets of RGCs
    • Contrast sensitivity
    • Movement perception
    • Color Vision
60
Q

RGC are primarily classified by their …?

A
  • projection to the LGN
    • Several subcategories
    • Morphologically distinct
    • Physiologically distinct
61
Q

What is the goal of function specific perimetry?

A
  • Attempts to isolate subpopulations of ganglion cells by evaluating a specific visual function characteristically processed by that cell type
  • When a single system is isolated by the function-specific perimetric test, relatively fewer cells are being tested at the same time
    • Less redundancy in the coverage of a given retinal location
    • Less overlap in response that could potentially “mask” ganglion cell losses
    • Earlier glaucomatous damage becomes easier to detect
62
Q

Short Wavelength Automated Perimetry (SWAP) is designed to assess what?

A
  • short wavelength sensitive color system
63
Q

Short Wavelength Automated Perimetry (SWAP) isolates __ cones.

A

blue cones

  • Send projects to blue-cone bipolar cells then project to small bistratified RGCS
  • Small bistratified RGCs projects to koniocellular layers of LGN
  • Encode BLUE - YELLOW opponency
    • BLUE ON: activates
    • YELLOW OFF: suppresses
64
Q

Before testing with SWAP, the patient should under go what to isolate blue cones?

A
  • adaptation period
  • 3 mins
  • bright yellow exposure
  • fatigues medium and long wavelength cones - isolating blue cones
65
Q

High risk OHT should be tested with both __ and __

A

SWAP & SAP

66
Q

Which one detects VF defects earlier? SWAP or SAP?

A

SWAP

  • Defects detected 3-5 years earlier
  • Pt with thinner cornea have higher prevalence of SWAP defects
  • Correlation between SWAP and RNFL or optic disc image are stronger (than SAP)
67
Q

What are some limiations of using SWAP?

A
  • Longer duration of the test
    • 15% longer
    • Takes 10-15 mins per eye
    • Length has been improved by advent of SITA-SWAP BUT
      • Still more difficult to recognize a blue target
      • Still takes longer
      • Still results in more patient fatigue
  • Higher test variability
    • Both short term (within test) and long term (from test to test)
  • Nuclear sclerosis can confound results
    • Yellow of lens acts like a blue-blocker
    • Adjustment of pattern deviation plot helps
  • May not be able to track ADVANCED cases of glc
    • Depth of field defects may be so deep that pt can not perceive the target at all
    • For ADVANCED glaucoma, conventional SAP should be used
68
Q

Should you use SAP or SWAP for advanced glaucoma?

A

SAP

69
Q

What is frequency doubling technology (FDT)?

A
  • Determines contrast sensitivity for the frequency doubling stimulus
  • This phenomenon mediated by subset of magnocellular RGCS
    • My cells
    • Represent 3-5% of all RGCS
    • A deficit would manifest even when small proportion of cells affected due to the reduced redundancy in coverage of a given location of retina
  • Results of FDT are predictive of future onset and location of functional loss assessed by SAP
70
Q

What is the difference between FDT and SAP?

A
  • FDT = predictive of future onset
    • able to show functional loss before SAP
  • SAP = assess functional loss
71
Q

How long does FDT threshold and suprathreshold take?

A
72
Q

FDT is able to detect progression __ - __ months before SAP

A

12-24

73
Q

What are 2 limitations of FDT?

A
  • Large stimulus - reduce ability to detect localized defects
  • Low number of targets presented
    • evaluating progressive damage over time is difficult
    • less valuable for glc f/u

Glaucoma (11 decks)

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