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Clinical and professional practice > visual fields recap > Flashcards

visual fields recap Flashcards

1
Q

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

A

3-5%

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2
Q

name the two basic classifications of visual field methods

A

static and kinetic

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3
Q

how is the kinetic visual field assessment carried out

A

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

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4
Q

what is static perimetry the best technique for

A

the detection and investigation of early field loss

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5
Q

why is detection of early field loss crucial

A

to detect primary open angle glaucoma

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6
Q

name the two classifications/strategies of static perimetry

A

threshold and supra threshold

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7
Q

name the two types of threshold static perimetry

A

full threshold and SITA/ZATA

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8
Q

how does the full threshold strategy work

A

each location is thresholded sing a staircase procedure

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9
Q

how does the SITA/ZATA strategy work

A

it is a quicker version of the full threshold strategy

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10
Q

how does the supra threshold strategy work

A

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

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11
Q

list 7 advantages of the threshold strategies for testing visual fields

A
  • 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
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12
Q

name a disadvantage of the threshold strategy for testing visual fields

A

time consuming

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13
Q

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

A
  • 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
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14
Q

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

A

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

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15
Q

name 3 types of visual field equipments for kinetic perimetry

A
  • gross perimetry/confrontation
  • arc perimeters
  • certain bowl perimeters e.g. goldman, octopus
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16
Q

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

A
  • automated perimeter - Humphrey field analyser and modern Henson models
  • automated/semi-automated perimeters - Henson for supra threshold testing
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17
Q

explain how the automated static perimeter works

A

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

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18
Q

explain how the semiautomated static perimeter works

A

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

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19
Q

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

A

SITA/ZATA fast threshold

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20
Q

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

A

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

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21
Q

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

A

sensitivity

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22
Q

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

A

gross perimetry/confrontation test

23
Q

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

A
  • kinetic methods on a bowl perimeter

- peripheral static methods on a HFA

24
Q

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

A

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
25
Q

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

A

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

26
Q

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

A

if the rx is above -5,00D

27
Q

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

A

+1.50

28
Q

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

A

+2.00

29
Q

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

A

50-54

30
Q

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

A

55-59

31
Q

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

A

60-64

32
Q

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

A

+4.00

33
Q

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

A

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

34
Q

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

A

full add

35
Q

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

A

bifocals, progressives and tinted glasses

36
Q

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

A
  • 26 retinal locations in 8 patterns
  • 68 retinal locations in 20 patterns
  • 136 retinal locations in 40 patterns
37
Q

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

A

you can miss an error/scotoma in visual fields

38
Q

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

A

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

39
Q

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

A

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

40
Q

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

A

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

41
Q

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

A
  • threshold related
  • three zone
  • quantify defect strategy
  • age reference strategy
42
Q

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

A

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

43
Q

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

A

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

44
Q

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

A
  • 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
45
Q

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

A

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

46
Q

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

A

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

47
Q

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

A

estermann vf test

48
Q

what is the estermann vf test used for

A

ascertaining whether fit to drive

49
Q

what correction will you use with the estermann vf test

A

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.

50
Q

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

A

fire fighters

51
Q

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

A

SITA fast 24-2

52
Q

when will you use an amsler chart

A

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

53
Q

at what distance is the amsler chart designed for

A

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

54
Q

name 2 limitations of the amsler chart as a screening tool

A
  • 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

Clinical and professional practice (16 decks)

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