Visual Fields 1

Question 1

general VF screening has ____ specificity and ___ sensitivity?

Answer 1

high specificity and good sensitivity

Question 2

why does general VF screening have high specificity?

Answer 2

high ability to show a normal VF in normal patients, few false field defects

Question 3

compromised specificity could cause:

Answer 3

many false field defects (missed points that are not due to true VF loss)

Question 4

compromised sensitivity could cause:

Answer 4

many true defects missed

Question 5

sensitivity is the ability to:

Answer 5

detect a VF defect when present

Question 6

specificity is the ability to:

Answer 6

identify a normal VF as normal

Question 7

100% sensitivity would mean:

Answer 7

all VF defects are detected

Question 8

100% specificity would mean:

Answer 8

all normal VFs are identified as normal, no false field defects

Question 9

what test do you run for Humphrey Field Analyzer (HFA)?

Answer 9

central 40 test

Question 10

what tests do you run for the FDT?

Answer 10

C20 or N30 (N30 better)

Question 11

what tests do you run for the Matrix?

Answer 11

C20 or N30 (N30 better)

Question 12

incidence of visual field loss in the general population is about

Answer 12

3-6% (incidence increases with age)

Question 13

code for problem specific VF screening

Answer 13

92081

Question 14

code for diagnostic perimetry

Answer 14

92082

Question 15

for diagnostic perimetry testing strategy, what is often needed?

Answer 15

some quantification of VF defects is needed-quantify defect or 3 zone strategy

Question 16

for diagnostic perimetry, what kind of test points are best?

Answer 16

best to use more test points to define the defect size, shape, borders, etc. (Full Field 120 example)

Question 17

code for quantitative perimetry

Answer 17

93083

Question 18

what is the purpose of quantitative perimetry?

Answer 18

to quantify the VF of a patient at higher risk of VF loss in order to detect the onset of VF loss as early as possible

Question 19

what is the typical testing strategy and point pattern for quantitative perimetry?

Answer 19

threshold (all points tested)- SITA standard or SITA fast with usually 50-76 points in the central field

Question 20

in quantitative perimetry, the thresholds (dB values) allow the ability to:

Answer 20

determine if the VF loss if getting deeper (lower dB values) with time

Question 21

quantitative perimetry has high sensitivity, which can result in what disadvantages?

Answer 21

• many more false defects with threshold perimetry and more difficult to interpret
• much longer testing time than screening VFs

Question 22

what type of perimetry (and code) for the highest reimbursement but most limited acceptable diagnoses?

Answer 22

quantitative perimetry (92083)

Question 23

normal monocular vision field, absolute limits for: superior

Answer 23

60

-highly variable

Question 24

normal monocular vision field, absolute limits for:

inferior

Answer 24

75

Question 25

normal monocular vision field, absolute limits for:

nasal

Answer 25

60

Question 26

normal monocular vision field, absolute limits for:

temporal

Answer 26

100

Question 27

normal monocular vision field, absolute limits for:

total lateral extent

Answer 27

160

Question 28

normal monocular vision field, absolute limits for:

total vertical extent

Answer 28

135

Question 29

total lateral extend for normal binocular vision field?

Answer 29

200

Question 30

central ___ to each side of fixation is binocular overlap

Answer 30

central 60

Question 31

the temporal ___ on each side of the binocular field is the monocular, temporal crescent

Answer 31

30-40

Question 32

what type of alternative perimetry is used in SWAP?

Answer 32

blue stimulus on yellow background for SWAP (short wavelength automated perimetry)

Question 33

what type of alternative perimetry is used in FDT (and Matrix)?

Answer 33

low spatial frequency grating undergoing rapid phase shift (frequency doubling illusion)

Question 34

where is the peak of the HOV and what does it mean?

Answer 34

sensitivity at the fovea is highest to white stimuli on a white background under photopic conditions

Question 35

where is the hole in the HOV?

Answer 35

15 degrees temporal to fixation (normal physiological blindspot)

Question 36

size of the physiological blindspot (BS)?

Answer 36

7.5 degrees vertical and 5.5 degrees horizontal (vertical oval shape)

Question 37

possible blind spot (BS) changes in glaucoma

Answer 37

BS may enlarge vertically in glaucoma but it is not a consistent early sign in glaucoma

Question 38

possible blind spot (BS) changes in papilledema

Answer 38

BS enlarges in all directions

ONH is swelling due to increased intracranial pressure

Question 39

how is BS used for perimetry?

Answer 39

BS used to check fixation quality in automated perimetry but its size/shape is not plotted for diagnostic purposes in modern automated perimetry

Question 40

in the HOV, the greater the height, the greater the:

Answer 40

sensitivity

Question 41

sensitivity at the peak of the HOV is the highest of all points and is about ___ dB higher than points just outside the fovea

Answer 41

3 or 4

Question 42

what is the sensitivity at the BS?

Answer 42

0 dB (absolute scotoma)

Question 43

sensitivity declines gradually from fixation to absolute limits of HOV, the slope is roughly:

Answer 43

3 dB per 10 degrees (in central 30 degrees)

Question 44

in the HOV, there is a steeper and more variable slope in ___ field

Answer 44

superior VF

Question 45

in the HOV, there is a flatter slope in the ___ field

Answer 45

temporal

Question 46

when does the variability occur in short term fluctuation?

Answer 46

during a test

Question 47

when does variability occur in long term fluctuation?

Answer 47

from test to test

Question 48

short term fluctuation, or variability of sensitivity or threshold during a test, can average about ____ dB

Answer 48

1 to 2.5 dB in central field

Question 49

short term fluctuation can be up to ___ dB in a single point in normals

Answer 49

6 dB

Question 50

where does short term fluctuation tend to be greater in the field?

Answer 50

tends to be greater further from fixation, greater in peripheral VF (outside of central 30)

Question 51

2 causes for increased short term fluctuation in central VF:

Answer 51

1. abnormal VF- VF loss especially in early glaucomatous VF loss
2. reduced patient reliability and consistency of responses

Question 52

how is the decibel, unit of current perimetry, a relative unit?

Answer 52

relative to the brightest stimulus available on the instrument- therefore dB values vary from brand to brand and cannot be compared between different brands and instruments

Question 53

on a decibel scale, what is the brightest stimulus available for that perimeter?

Answer 53

0 dB

Question 54

10 dB would be what brightness compared to the brightest stimulus?

Answer 54

1/10 of the brightness of the brightest stimulus available on that perimeter

Question 55

how are dB directly related to sensitivity?

Answer 55

the higher the sensitivity, the higher the dB value

Question 56

highest dB value is normally at the:

Answer 56

fovea (the fixation point of the VF)