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clinical skills > Visual Fields part 2 > Flashcards

Visual Fields part 2 Flashcards

1
Q

what is static perimetry?

A

a stimulus in fixed size and stimulus is moved from a non seeing area to a seeing area until it is detected by px

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2
Q

what is static perimetry?

A

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

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3
Q

what does the retina have?

A

every point in the retina has a certain threshold sensitivity

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4
Q

what is static perimetry recorded ?

A

decibels or log unit

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5
Q

what does a high number mean?

A

high number means the higher the threshold sensitivity the dimmer the light detected

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6
Q

What is the max luminance?

A

max luminance is 0 dB

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7
Q

where are high and lower threshold sensitivity recorded?

A

higher threshold sensitivity are recorded in central locations

lower threshold sensitivity are recorded in peripheral locations

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8
Q

How do you compensate change in sensitivity across the visual field?

A

Varying the stimulus luminance

varying stimulus size

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9
Q

What types of static perimetry are there?

A

supra threshold screening

Full threshold

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10
Q

what is supra threshold screening?

A

a stimulus is seen above a certain threshold

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11
Q

What is full threshold?

A

measures precise threshold sensitivity by varying stimuli intensities

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12
Q

How does supra threshold screening work?

A

stimuli presented a certain number of dB av
above threshold at each point within visual field
any stimuli falling within a scotoma will not be seen

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13
Q

what is suprathreshold TWO ZONE?

A

show stimuli, px reports cant see
show stimuli again, if px sees it then mark with circle if px can see again mark black
= two responses

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14
Q

How many responses does suprathreshold TWO ZONE have?

A

two responses

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15
Q

what is suprathreshold THREE ZONE?

A

points missed twice are shown a stimulus of max luminance, if seen marked with an X (relaive defect ) if not seen marked as black (absolute defect )

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16
Q

How is supra threshold related?

A

Age related Supra-threshold

Threshold related supra-threshold

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17
Q

how does the age related supra-threshold strategy work?

A

since age is the primary factor, some instruments base the suprathreshold on normative data for various age groups
e.g 70 years old will compare with normal 70 year old

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18
Q

what is the stimuli in age related supra threshold?

A

stimuli is set at certain number of dB higher that age matched normal

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19
Q

how does the threshold related supra threshold strategy work?

A

determines the threshold for 4 points within the visual field. show stimulus cant see it, make it 4dB bright can see it make it 2dB dimmer until they cant see it

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20
Q

what is the stimuli in age related threshold related supra threshold?

A

set supra threshold testing level at a certain number of dB above the 2nd most sensitive point of 4 measurement is their threshold sensitivity and makes it couple dB brighter thats how they know what you should see

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21
Q

supra threshold screening can be measured by ?

A

No quantification

with quantification

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22
Q

what is no quantification?

A

examiner simply notes the stimuli that are not seen

no attempt to quantify the depth of scotoma

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23
Q

what is quantification?

A

if any suprathreshold stimuli is missed the depth of the scotoma is assessed by establishing threshold

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24
Q

which software provides supra threshold strategy?

A

Henson software

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25
Q

what two versions of henson supra threshold are there ?

A

multiple stimulus supra threshold strategy

Single stimulus supra threshold strategy

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26
Q

How does Single stimulus supra threshold strategy work?

A

> stimulus presented on at a time 5dB above a measurement of px threshold
stimuli not seen presented a second time at same intensity
if missed on both ocasions the stimuli is presented 8dB the 12dB above threshold estimate
a grey scale indicates the depth of defect
5dB 8dB 12dB

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27
Q

How does multiple stimulus supra threshold strategy work?

A

> multiple stimulus presented simultaneously
patient report how many lights seen
if any not seen, position of unseen stimulus is deduced and recorded
2, 3 or 4 stimulus patterns shown
at the start determine px threshold and stimuli presented 5dB above threshold

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28
Q

How far does multiple stimuli supra threshold work?

A

26 to 68 or 136 locations

29
Q

when do you use 136 location?

A

if you have small scotoma

30
Q

What is the advantage of supra threshold?

A

–Rapid examination time
–Easier for patient
–90% higher chance in detecting glaucoma
stimuli sampling density to 136 point screening

31
Q

What is the disadvantage of supra threshold?

A

not as accurate as full threshold perimetry less information

32
Q

What is full threshold?

A

a staircase procedure used to estimate the threshold according to a pre determined set of rules based upon a knowledge of normal age related thresholds

33
Q

what softwares measure full threshold?

A

SITA

ZATA

34
Q

Which software is SITA used for?

A

SITA for the humphrey

35
Q

Which software is ZATA used for?

A

ZATA for henson

36
Q

what does the staircase procedure involve?

A

> starting stimulus selected from age
double crossing of threshold
threshold recorded as last seen stimulus
termed 4-2dB staircase
shows light px cannot see then makes it 4dB brighter.

37
Q

What should an ideal threshold algorithm have?

A

properties such as:
accuracy
reproducibility
offer rapid examination time

38
Q

Does the standard full threshold algrithm fulfil all of these criterias?

A

No

39
Q

What does SITA stand for?

A

swedish interactive threshold algorithms

40
Q

What does ZATA stand for?

A

Zippy adaptive threshold algorithms

41
Q

What is good about SITA?

A

sita standard is approx 50% faster than standard full threshold algorith

sita fast is approx 75% faster than the standarad full threshold algorithm

42
Q

which accuracy is better for SITA?

A

Accuracy of SITA standard is slightly better than standard full threshold algorithm and is less susceptible to fatigue effect (5-7 mins)

accuracy of SITA fast not as good as standrad full threshold algorithm

43
Q

what is good about ZATA ?

A

test is much faster than full threshold programs and also more accurate

Zata program uses data from prev visual field result or age dependent normal values making it faster

44
Q

what is good about ZATA fast?

A

ZATA fast has looser terminating criteria than ZATA standard making it faster but less accurate

45
Q

How does SITA save time?

A
  • speed of stimulus adjusted to the patient
  • post test analysis
  • reduction in number of catch trails
  • based on models normal and abnormal visual fields
  • used to predict future responses and speed up testing times
46
Q

what does 10-2 central visual field mean?

A

central 10 degrees

47
Q

what does 24-2 central visual field mean?

A

24 degrees

48
Q

what does 30-2 central mean ?

A

central 30 degrees

49
Q

which degrees does full threshold measure?

A

10-2
24-2
30-2

50
Q

which degree does SITA measure?

A

SITA ( 10-2, 24-2. 30-2)

51
Q

which degree does ZATA measure?

A

ZATA ( 10-2, 24-2)

52
Q

which full threshold can measure centre and peripheral visual field?

A

SITA

53
Q

which full threshold can not measure peripheral visual field?

A

ZATA

54
Q

what is the advantage of FULL threshold?

A

:enables statistical analysis
: provides diagnostic information
: can monitor visual field progression
: provides information about the reliability of the data

55
Q

what is the disadvantage of FULL threshold?

A

: generally more time consuming than supra threshold

: although newer threshold procedures offer a comparable examination time

56
Q

Which test can be used for driving?

A

Estermann visual field test

57
Q

How does Estermann VF work>?

A

binocular both eyes

no trail lenses required. if px has glasses can wear them

58
Q

what does the estermann VF test do?

A

used to ascertain whether fit to drive

59
Q

what does amsler chart test used for?

A

used to measure central ten degrees of macula

60
Q

how do you use amsler chart?

A

ask px if any of the lines are missing or distored

61
Q

what distance do you use the amsler chart?

A

test isdesigned for 28-32cm so the patient should be corrected for the distance

62
Q

which visual field test do you think you might choose for a 80 year old px who has senile dementia and nil pathology?

A

Supra threshold single stimulus

63
Q

which visual field tests are more commonly used in an ophthalmology clinic?

A

SITA standard

SITA fast

64
Q

which visual field test might you suggest to carry out on a 60 year old in whom and eye examination revealed nil pathology however they have a family history of glaucoma?

A

supra threshold multiple stimulus

65
Q

which visual field test might you suggest to use on a 60 year old with advanced glaucoma ?

A

full threshold 24-2

66
Q

if you have nil pathology which test should you use?

A

suprathreshold
: multiple stimulus 68 points ( henson )
: single stimulus 68 points ( henson )
: c-76 quantify (Humphrey )

67
Q

if you have pathology what do you use?

A

SITA 24-2 fast - henson
ZATA 24-4 fast -humphrey
smaller or larger field size based on pathology

68
Q

if px have nil pathology however risk factor ( Disc , IOP, FOH)

A

consider SITA ZATA

69
Q

What would you do to see macula problem?

A

Amsler test chart

clinical skills (13 decks)

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