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Flashcards in Visual Field 3 Deck (34)
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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?

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


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


what does SITA stand for

swedish interactive threshold algorithm


what does SITA compute threshold based on

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


how does SITA estimate false positive responses

does not test directly
uses response time to estimate false + responses


when does SITA retest threshold

if the values are 12 dB off
(others retest at 7dB)


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


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


what does short wavelenght automated perimetry (SWAP) use?

uses blue target and yellow background


what technique is used for a full threshold test

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


what is the full threshold 4-2 algorithm

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


we lose a decibel a decade after age ____



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

10 degrees


at fixation, how many dB should it be

32 dB


what is the mean deviation (MD)

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


what is total deviation

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


what does P < 2 mean

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


what is pattern deviation

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


what is pattern standard deviation (PSD)

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


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

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


what is visual field index (VFI)

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


what does a VFI of 90% mean

90% of visual field is normal


VFI is plotted against _____



____% 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



what is a change analysis box plot

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


what is a guided progression analysis (GPA)

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


what is likely progression in GPA?
what is possible progression

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


what are the different screening modes on the humphrey

2 zone strategy
3 zone strat
quantify defects


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

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


what is the 2 zone strategy

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


what is the 3 zone strategy

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


what is the brightest stimulus for the humphrey

10,000 asb