visual fields lec 2: static perimetry

Question 1

what is kinetic perimetry

Answer 1

when a stimulus of a fixed size/luminance is moved from non-seeing to seeing until it is detected by the patient

Question 2

what is static visual field analysis/perimetry

Answer 2

the visual field is probed at specific static points and threshold sensitivity is recorded

Question 3

what does every point on the retina have

Answer 3

a certain threshold sensitivity

Question 4

what is threshold sensitivity recorded as in static perimetry

Answer 4

decibels or log units

Question 5

what does it mean if the decibel or log unit is higher

Answer 5

the higher the threshold sensitivity i.e. the dimmer the light detected (as can see more)

Question 6

what is 0 DB

Answer 6

the maximum stimulus luminance of a perimeter i.e. the maximum possible brightness

Question 7

which part of the retina is higher threshold sensitivities recorded

Answer 7

central retina

Question 8

which part of the retina are lower sensitivity thresholds recorded

Answer 8

peripheral locations of the retina

Question 9

what does static visual field analysis compensate for, and how does it achieve this

Answer 9

compensates for the change in sensitivity across the visual field, achieved by

• varying stimulus luminance e.g. brighter
• varying stimulus size e.g. bigger

Question 10

name the two types of measuring static perimetry

Answer 10

• supra threshold screening

- threshold

Question 11

how does threshold work

Answer 11

measures the precise threshold sensitivity by varying stimuli intensities at every single location

Question 12

what is indicated if a px does not see the stimulus when using supra threshold

Answer 12

chances are they have a pathology if they can’t see the stimulus

Question 13

what happens to a stimuli that falls in a scotoma on supra threshold screening

Answer 13

the stimuli will not be seen

Question 14

in supra threshold with quantification technique, what does a higher number in the visual field plot mean

Answer 14

higher threshold sensitivity in DB and this indicates the depth of scotoma

Question 15

how is the single stimulus supra threshold strategy set up

Answer 15

the test is full automatic and requires no intervention by the perimetrist other than setting the patient up and giving the instructions

Question 16

explain how the single stimulus supra threshold strategy works

Answer 16

• stimuli is presented at one time 5 db above the measurement of the px threshold sensitivity
• if the stimuli is not seen, then present a second time at the same intensity
• if the stimuli has been missed on both occasions, then the stimuli is presented at 8 db then at 12db above the threshold estimate
• the grey scale indicates the depth of the defect, whether its at 5db, 8db or 12db

Question 17

what are the three types of threshold programmes

Answer 17

• full threshold (not used anymore)
• SITA for the humphrey
• ZATA for the henson

Question 18

how does the standard threshold staircase procedure work

Answer 18

• starting stimulus is selected from the px’s age
• then theres a double crossing of the threshold (e.g. from non seeing, then make the stimuli 4db higher, then 4 more db higher, once px can see stimuli, reduce by 2db dimmer and a further 2db dimmer until px can’t see it again etc)
• threshold recorded as last seen stimulus
• termed a 4-2db staircase
• abbreviated staircase procedure exhibits low threshold variability “gold standard” in perimetry

Question 19

what are the two new generation algorithms which are used instead

Answer 19

• humphrey: swedish interactive threshold algorithms (SITA)

- henson: zippy adaptive threshold algorithms (ZATA)

Question 20

what are the two SITA programmes available on the humphrey

Answer 20

• SITA standard

- SITA fast

Question 21

how much more faster is SITA standard, than the standard full threshold algorithm

Answer 21

50% faster (takes about 5-7 min)

Question 22

how much more faster is SITA fast, than the standard full threshold algorithm

Answer 22

75% faster (takes about 2-5 min)

Question 23

which threshold programme is more accurate and which one is less accurate than the standard full threshold programme and why

Answer 23

• SITA standard is more accurate than full threshold algorithm as the px is less susceptible to the fatigue affect
• SITA fast is not as accurate as the standard full threshold algorithm

Question 24

how does the SITA threshold programme save time? state 3 points

Answer 24

based on models of normal and abnormal (glaucomatous) visual fields:

• it is used to predict future responses and speed up testing time, so the speed of the stimulus is adjusted to that of the patient (if press button faster, the programme goes faster)
• post test analysis
• reduction in number of catch trials

Question 25

what two types of ZATA programmes are there

Answer 25

- ZATA standard (accurate) | - ZATA fast (speed)

Question 26

how is the ZATA threshold programme compared to the full threshold programme

Answer 26

it is faster and more accurate

Question 27

what data does the ZATA programme use and what advantage does this have

Answer 27

uses data from any previous visual field result or age dependent normal values, making it faster

Question 28

how is the ZATA fast compared to ZATA standard

Answer 28

ZATA fast has a lower terminating criteria than ZATA standard, making it faster but less accurate

Question 29

what are the three different central measurements that threshold can measure

Answer 29

- 10-2 central: 10 degrees - 24-2 central: 24 degrees - 30-2 central: 30 degrees based on where the pathology is

Question 30

which central measurement, measures further out in the visual field

Answer 30

30-2 central: 30 degrees

Question 31

which central measurements can full threshold measure

Answer 31

10-2 24-2 30-2

Question 32

which central measurements can SITA measure

Answer 32

10-2 24-2 30-2

Question 33

which central measurements can ZATA measure

Answer 33

10-2 | 24-2

Question 34

list 4 advantages of threshold

Answer 34

- enables statistical analysis - provides diagnostic information - can monitor visual field progression (glaucoma) - provides information about reliability of the data

Question 35

list 2 disadvantages of threshold

Answer 35

- more time consuming that supra threshold - it is easier to supra threshold although newer threshold procedures offer a comparable examination time

Question 36

when is the estermann visual field test in the humphrey used

Answer 36

used for ascertaining whether fit to drive

Question 37

how is the estermann visual field test in the humphrey carried out

Answer 37

- binocular (both eyes) field test - no trial lenses - if requires rx to function daily then use actual glasses (because px may use a chunky frame, but do with both specs and trial lenses in order to see if a scotoma is due to the px's frames) - if do not require rx to function daily to drive then do not use an rx during test

Question 38

at what eccentricity is an ambler chart used to measure

Answer 38

central 10 degrees i.e. testing the macula

Question 39

what is the ambler chart used for

Answer 39

it is valuable in testing a suspicious macula, or if unable to see the macula

Question 40

what do you ask the patient when using an amasser chart on them

Answer 40

ask if any lines are missing or distorted

Question 41

what should the patient be corrected for when using the amasser chart and why

Answer 41

patient should be corrected for near distance as the test is designed for 28-32 cm

Question 42

which visual field test will you use on a 80 year old patient with senile dementia in whom an eye examination revealed nil pathology and state why

Answer 42

supra threshold single stimulus | as single stimulus is easier for someone with dementia and nil pathology use supra threshold

Question 43

which visual field tests are most commonly used in an ophthalmology clinic and state why

Answer 43

- SITA standard - SITA fast (either as the px will have a pathology if they're at a ophthalmology clinic, but SITA standard is longer so the px can lose accuracy)

Question 44

which visual field test will you carry out on a 60 year old in whom an eye examination revealed nil pathology, however they have family history of glaucoma

Answer 44

SITA fast 24-2

Question 45

which visual field test will you use on a 60 year old with advanced glaucoma and why

Answer 45

SITA standard 10-2 | they have lost a lot of peripheral visual field, so cannot see whats left

Question 46

what rx will you use in a 60 year old patient carrying out a 30-2 full threshold? Distance correction: RE: -4.50/+1.50x80 LE: -4.50/+3.00x90 Reading addition: +1.50 either eye

Answer 46

RE: -3.00/+1.50x80 LE: -3.00/+3.00x90 use distance rx + reading add, and keep cyl in as it is above 1D

Question 47

list the programmes you will use on a patient with nil pathology

Answer 47

supra threshold - multiple stimulus 68 points (henson) - single stimulus 68 points (henson) - c-76 quantify (humphrey)

Question 48

when will you use less points on a patient

Answer 48

if they struggle concentrating

Question 49

when will you use more points on a patient

Answer 49

if they have a suspect small scotoma

Question 50

which settings will you use on a patient who has a pathology

Answer 50

- SITA 24-2 (fast) (henson) - ZATA 24-2 (fast) (humphrey) smaller or larger field size based on pathology

Question 51

which settings will you use on a patient with nil pathology however they have a risk factor (disc, IOP, FOH)

Answer 51

SITA or ZATA

Question 52

An automated perimeter can run two tests. What are the two tests?

Answer 52

- threshold tests | - screening tests

Question 53

Screening tests are used for?

Answer 53

Detection of a defect

Question 54

Threshold tests are used for?

Answer 54

Assessment of a defect

Question 55

Name 3 differences of a threshold test vs a screening test on an automated perimeter.

Answer 55

- Threshold tests takes LONGER than a screening test | - more accurate than a screening test

Question 56

The major advantage of a screening test on an automated perimeter.

Answer 56

Its a fast test to run.

Question 57

The disadvantage of a screening test on an automated perimeter is

Answer 57

It’s more inaccurate than the threshold tests due to limited data quantification