visual fields recap

Question 1

what is the incidence of visual field loss in the general public

Answer 1

3-5%

Question 2

name the two basic classifications of visual field methods

Answer 2

static and kinetic

Question 3

how is the kinetic visual field assessment carried out

Answer 3

start from a non seeing area and move in until px detects the target

Question 4

what is static perimetry the best technique for

Answer 4

the detection and investigation of early field loss

Question 5

why is detection of early field loss crucial

Answer 5

to detect primary open angle glaucoma

Question 6

name the two classifications/strategies of static perimetry

Answer 6

threshold and supra threshold

Question 7

name the two types of threshold static perimetry

Answer 7

full threshold and SITA/ZATA

Question 8

how does the full threshold strategy work

Answer 8

each location is thresholded sing a staircase procedure

Question 9

how does the SITA/ZATA strategy work

Answer 9

it is a quicker version of the full threshold strategy

Question 10

how does the supra threshold strategy work

Answer 10

stimuli are first presented at an intensity that is calculated to be above the patient’s threshold, if the stimuli are seen, then it is assumed that no significant defect exists

Question 11

list 7 advantages of the threshold strategies for testing visual fields

Answer 11

• sensitive to shallow field loss and early fluctuations in glaucomatous VF loss
• visual field progression (glaucoma)
• allows statistical analysis
• diagnostic information
• provides information about reliability of the data
• highly skilled perimetrist not needed
• reproducible VF test/testing conditions

Question 12

name a disadvantage of the threshold strategy for testing visual fields

Answer 12

time consuming

Question 13

name 3 advantages of the supra threshold strategy for testing visual fields

Answer 13

• multiple or single stimulus has enabled speed up of investigation and able to assess visual fields on every visit
• good screening test
• no need for highly trained perimetrist

Question 14

name a disadvantage of the supra threshold strategy for testing visual fields

Answer 14

insensitivity to shallow visual field defects = poor detection of early POAG

Question 15

name 3 types of visual field equipments for kinetic perimetry

Answer 15

• gross perimetry/confrontation
• arc perimeters
• certain bowl perimeters e.g. goldman, octopus

Question 16

name 2 types of static perimeters and give examples of the manufacturers that do them

Answer 16

• automated perimeter - Humphrey field analyser and modern Henson models
• automated/semi-automated perimeters - Henson for supra threshold testing

Question 17

explain how the automated static perimeter works

Answer 17

the decision making process of the examination strategy is exclusively controlled by the computer and does not require intervention of the operator

Question 18

explain how the semiautomated static perimeter works

Answer 18

some field tests require the operator to control the examination strategy
e.g. we have to find the patients threshold, or during multiple stimulus when we have to ask the patient how many lights they can see

Question 19

what test strategy will you use on a patient who has family history of glaucoma

Answer 19

SITA/ZATA fast threshold

Question 20

when would it be useful to carry out gross perimetry/confrontation test on a patient

Answer 20

in investigating patients who will benefit from a more detailed investigation of their peripheral fields

Question 21

what is found to be low with gross perimetry/confrontation test

Answer 21

sensitivity

Question 22

if a patient has poor visual acuity, which test is best to analyse their visual fields

Answer 22

gross perimetry/confrontation test

Question 23

if you require further peripheral investigation after using the gross perimetry/confrontation test on a patient, what other 2 options can you use

Answer 23

• kinetic methods on a bowl perimeter

- peripheral static methods on a HFA

Question 24

should a rx be worn for gross perimetry/confrontation test and why

Answer 24

no prescription should be worn for a peripheral fields, because:

• peripheral acuity is poor whether the refractive error is corrected or not
• frames and the periphery of lenses can interfere with peripheral field

Question 25

in which case may it be worth doing a peripheral field with and without the rx

Answer 25

very high refractive error: +/- 8D or more, too see if there is any difference

Question 26

when carrying out static perimetry, and measureing the central 30 degrees of visual field, when must an rx be worn

Answer 26

if the rx is above -5,00D

Question 27

what add should be used on top of a distance rx for a 40-44 y/o

Answer 27

+1.50

Question 28

what add should be used on top of a distance rx for a 45-49 y/o

Answer 28

+2.00

Question 29

for what age group should a +2.50 add be used on top of a distance rx

Answer 29

50-54

Question 30

for what age group should a +3.00 add be used on top of a distance rx

Answer 30

55-59

Question 31

for what age group should a +3.50 add be used on top of s distance rx

Answer 31

60-64

Question 32

what add should be used on top of a distance rx for a +64 y/o

Answer 32

+4.00

Question 33

when will you use BVS and when will you not, when using a patient's rx during visual fields

Answer 33

BVS is cyl is less than 1.00DC and use cyl in lens holder or use px own rx if cyl more than 1.00DC

Question 34

what rx will you use on a px who is fully cyclopeged during visual fields

Answer 34

full add

Question 35

which type of lenses should be used only as a last resort when during visual fields

Answer 35

bifocals, progressives and tinted glasses

Question 36

list the three different levels of investigations available with the Henson supra threshold programme and the amount of patterns for each level of investigation

Answer 36

- 26 retinal locations in 8 patterns - 68 retinal locations in 20 patterns - 136 retinal locations in 40 patterns

Question 37

what is a disadvantage to using the 26 retinal locations level in the Henson

Answer 37

you can miss an error/scotoma in visual fields

Question 38

when will you decide to use the 136 retinal locations level in the Henson

Answer 38

if missed lights in the 68 retinal point setting and want to establish the extent of the defect

Question 39

when will you decide to use the 68 retinal locations level in the Henson

Answer 39

for patients where the field defect is suspected other reasons for performing a more rigorous test

Question 40

why will you measure a patients threshold instead of setting it by age on the Henson

Answer 40

because the vf machine will assume that everyones threshold is the same

Question 41

list the 4 types of supra threshold strategies available on the humphrey

Answer 41

- threshold related - three zone - quantify defect strategy - age reference strategy

Question 42

how does the threshold related type of supra threshold strategy work on the humphrey

Answer 42

an expected hill of vision is calculated and the stimulus intensity is set 6DB brighter than expected at each location

Question 43

how does the three zone type of supra threshold strategy work on the Humphrey

Answer 43

the expected hill of vision is calculated as in threshold related e.g. 6DB brighter than expected at each location and the defects are classified as relative or absolute

Question 44

what does relative and absolute stand for in the three zone type of supra threshold strategy on the Henson

Answer 44

- relative defect = if point missed the first time then the vf machine shows a brighter stimulus, if the patient gets the brighter stimulus then it is a relative defect - absolute defect = if the patient misses the stimulus a second time which is at a brighter level than the first, then the brightest stimulus will be shown, if the patient misses this then it is classified as an absolute defect

Question 45

how does the quantify defect type of supra threshold strategy work on the humphrey

Answer 45

locations missed twice at screening level are thresholded, so the depth of the scotoma is assessed by establishing the threshold

Question 46

how does the age reference type of supra threshold strategy work on the Humphrey

Answer 46

the expected hill of vision is estimated from the patient's birth date

Question 47

which programme requires both eyes to be tested at the same time

Answer 47

estermann vf test

Question 48

what is the estermann vf test used for

Answer 48

ascertaining whether fit to drive

Question 49

what correction will you use with the estermann vf test

Answer 49

no trial lenses are used, if px requires an rx to function daily then use actual glasses, if does not require an rx to function daily then do not use an rx, the same applies to tinted specs.

Question 50

other than drivers, who else is the estermann vf test used on

Answer 50

fire fighters

Question 51

what visual field test will you do if a patient has symptoms or has a FHG

Answer 51

SITA fast 24-2

Question 52

when will you use an amsler chart

Answer 52

if you see a suspicious macula, or if you are unable to see the macula

Question 53

at what distance is the amsler chart designed for

Answer 53

28-32cm, so the patient should be corrected for this distance

Question 54

name 2 limitations of the amsler chart as a screening tool

Answer 54

- only detects 50% of patients with macular disease = poor sensitivity - will incorrectly identify about 2% of patients as having a scotoma when they do not have one