Visual Field 3

Question 1

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?

Answer 1

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

Question 2

what does SITA stand for

Answer 2

swedish interactive threshold algorithm

Question 3

what does SITA compute threshold based on

Answer 3

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

Question 4

how does SITA estimate false positive responses

Answer 4

does not test directly

uses response time to estimate false + responses

Question 5

when does SITA retest threshold

Answer 5

if the values are 12 dB off

others retest at 7dB

Question 6

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

Answer 6

40%

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

Question 7

what does short wavelenght automated perimetry (SWAP) use?

Answer 7

uses blue target and yellow background

Question 8

what technique is used for a full threshold test

Answer 8

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

Question 9

what is the full threshold 4-2 algorithm

Answer 9

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

Question 10

we lose a decibel a decade after age ____

Answer 10

20

Question 11

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

Answer 11

3dB

10 degrees

Question 12

at fixation, how many dB should it be

Answer 12

32 dB

Question 13

what is the mean deviation (MD)

Answer 13

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

Question 14

what is total deviation

Answer 14

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

Question 15

what does P < 2 mean

Answer 15

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

Question 16

what is pattern deviation

Answer 16

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

Question 17

what is pattern standard deviation (PSD)

Answer 17

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

Question 18

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

Answer 18

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

Question 19

what is visual field index (VFI)

Answer 19

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

Question 20

what does a VFI of 90% mean

Answer 20

90% of visual field is normal

Question 21

VFI is plotted against _____

Answer 21

age

Question 22

____% 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

Answer 22

40%

20%

Question 23

what is a change analysis box plot

Answer 23

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

Question 24

what is a guided progression analysis (GPA)

Answer 24

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

Question 25

what is likely progression in GPA? | what is possible progression

Answer 25

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

Question 26

what are the different screening modes on the humphrey

Answer 26

2 zone strategy 3 zone strat quantify defects

Question 27

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

Answer 27

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

Question 28

what is the 2 zone strategy

Answer 28

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

Question 29

what is the 3 zone strategy

Answer 29

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

Question 30

what is the brightest stimulus for the humphrey

Answer 30

10,000 asb

Question 31

what is a quantify defects

Answer 31

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

Question 32

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

Answer 32

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

Question 33

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

Answer 33

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

Question 34

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...

Answer 34

it problaby does not represent a defect if it is beyond 20 degrees it probalby rep a defect they probably represent a defect