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Glaucoma > Visual Field 3 > Flashcards

Visual Field 3 Flashcards

1
Q

what is the FASTPC strategy to get threshold?

what is the threshold

how many transitions does it make from seeing to nonseeing or vice versa?

A

machine uses technique to figure out threshold (using points based off 25 db initially)

  • shows a stimulus 2 dB dimmer than the expected threshold
  • then travels down in dB (up in brightness) in intervals of 3 until pt switches from not seeing to seeing.

-point of seeing = threshold

1

ex. if machine things pt should have threshold of 28 dB at a given point
30 dB => 27 dB seen.
-27 = threshold

ex. 30 dB not seen => 27 dB not seen => 24 dB seen
- 24 = threshold

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2
Q

what does SITA stand for

A

swedish interactive threshold algorithm

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3
Q

what does SITA compute threshold based on

A

computes threshold based on points w/ 50% probability of being seen

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4
Q

how does SITA estimate false positive responses

A

does not test directly

uses response time to estimate false + responses

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5
Q

when does SITA retest threshold

A

if the values are 12 dB off

others retest at 7dB

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6
Q

SITA programs are about ____% faster than the programs they resplace

A

40%

ex. SITA standard is 40% faster than full threshold
SITA Fast is 40% faster than FASTPAC

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7
Q

what does short wavelenght automated perimetry (SWAP) use?

A

uses blue target and yellow background

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8
Q

what technique is used for a full threshold test

A

4-2-2 staircase used w/ the last seen value taken as the pt’s threshold
-goes in 2 dB steps once it has crossed the line from seeing to non seeing or vice versa

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9
Q

what is the full threshold 4-2 algorithm

A

transition is crossed at least twice (from seeing to non seeing or vice versa)
ex. 27 seen => 31 not seen => 29 seen

-threshold is 29

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10
Q

we lose a decibel a decade after age ____

A

20

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11
Q

the hill of vision changes roughly ____dB every ____ degrees throughout the field

A

3dB

10 degrees

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12
Q

at fixation, how many dB should it be

A

32 dB

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13
Q

what is the mean deviation (MD)

A

avg elevation/depression of pts field compared to a normal/reference visual field

ex. if the class avg is 80 and you scored a 75 your MD would be -5.00

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14
Q

what is total deviation

A

shows what the difference/deviation is at each individual spot, when compared to corrected normal for pts age

ex. a spot with +3 means pt has 3 more dBs than “normal”
- they are at a 29 rather than a 26

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15
Q

what does P < 2 mean

A

less than 2% of the normal pop shows an MD larger than the value found in this test

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16
Q

what is pattern deviation

A

similar to TD except the results are adjusted for the overall changes in the height of the measured hill of vision

17
Q

what is pattern standard deviation (PSD)

A

a measurement of the degree to which the shape of the pts measured field departs from the normal corrected reference field

18
Q

what does low PSD equal?
high PSD?
what is an abnormal PSD?

A

low PSD equals a smooth hill
high PSD indicates an irregular hill
usually a PSD of over 3 is considered abnormal

19
Q

what is visual field index (VFI)

A

enhanced MD designed to be less effected by cataract, and more sensitive to changes near the center of the visual field to correlate better w/ ganglion cell loss

20
Q

what does a VFI of 90% mean

A

90% of visual field is normal

21
Q

VFI is plotted against _____

A

age

22
Q

____% of fibers can be lost and a pt can still have a normal field.
-need ____% of fibers to be lost to get only a 5dB defect

A

40%

20%

23
Q

what is a change analysis box plot

A

modified histogram, shows what is happening to the field over time

24
Q

what is a guided progression analysis (GPA)

A

pick 2 previous fields, avg them, compare to today’s test

25
Q

what is likely progression in GPA?

what is possible progression

A

likely: where 3 or more points show deterioration in at least 2 consecutives tests
possible: in cases wehre 3 or more points show deterioration on at least 3 consecutvie tests

26
Q

what are the different screening modes on the humphrey

A

2 zone strategy
3 zone strat
quantify defects

27
Q

what are the 2 different ways a screening field forms a hill output?

A
  1. four primary points, one in each quadrant are thresholded.
    - 2nd most sensitiv value is used to calculate the expected heigh of the hill of vision
  2. machine sets an age-corrected hill. could be diff correction but age related is the most common
28
Q

what is the 2 zone strategy

A

from expected height, theoretical hill of vision is calculated

  • targets then presented 6dB brighter than the theoretical hill of vision
  • if the point isn’t seen at 6dB it is tested again.
  • points missed twice at the 6dB brigher level are recorded as defects and a solid block is recorded
29
Q

what is the 3 zone strategy

A

get a theoretical hill (either 4 primary points or age related hill)

  • targets then presented 6dB brigher than theoretical hill of vision
  • points missed twice at 6dB level are retested w/ brightest stimulus for the machine
  • if see at brightest level an “x” is recorded
  • if not seen, a solid block is recorded

-usful for pts who have had strokes

30
Q

what is the brightest stimulus for the humphrey

A

10,000 asb

31
Q

what is a quantify defects

A

begins same as 2 zone strat

  • targets presented 6dB briger than the theoretical hill of vision
  • if missed twice the area is then thresholded
  • the number expressed is the diff btwn what was expected for the pts threshold and what it actually was, NOT THE ACTUAL THRESHOLD VALUE
32
Q

is a higher number better or worse for humphrey quantify defects?
what about for full thresholding tests?

A

quat: higher the number the worse
full: higher the better

33
Q

what does a negative number mean for humphrey quantify defect mode?

A

the point was missed during screening, but when the point was thresholded the value was better than the theoretical threshold
-better than expected

34
Q

if one isolated point is missed and the defect depth is less than or equal to 8dB…..

if one point is missed and the defect depth is greater than 8db…

if 2 adjacent points are missed w/ a defect depth of 6dB or higher…

A

it problaby does not represent a defect if it is beyond 20 degrees

it probalby rep a defect

they probably represent a defect

Glaucoma (4 decks)

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