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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
what two versions of henson supra threshold are there ?
multiple stimulus supra threshold strategy | Single stimulus supra threshold strategy
26
How does Single stimulus supra threshold strategy work?
> 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
27
How does multiple stimulus supra threshold strategy work?
>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
28
How far does multiple stimuli supra threshold work?
26 to 68 or 136 locations
29
when do you use 136 location?
if you have small scotoma
30
What is the advantage of supra threshold?
--Rapid examination time --Easier for patient --90% higher chance in detecting glaucoma stimuli sampling density to 136 point screening
31
What is the disadvantage of supra threshold?
not as accurate as full threshold perimetry less information
32
What is full threshold?
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
what softwares measure full threshold?
SITA | ZATA
34
Which software is SITA used for?
SITA for the humphrey
35
Which software is ZATA used for?
ZATA for henson
36
what does the staircase procedure involve?
> 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
What should an ideal threshold algorithm have?
properties such as: accuracy reproducibility offer rapid examination time
38
Does the standard full threshold algrithm fulfil all of these criterias?
No
39
What does SITA stand for?
swedish interactive threshold algorithms
40
What does ZATA stand for?
Zippy adaptive threshold algorithms
41
What is good about SITA?
sita standard is approx 50% faster than standard full threshold algorith sita fast is approx 75% faster than the standarad full threshold algorithm
42
which accuracy is better for SITA?
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
what is good about ZATA ?
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
what is good about ZATA fast?
ZATA fast has looser terminating criteria than ZATA standard making it faster but less accurate
45
How does SITA save time?
- 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
what does 10-2 central visual field mean?
central 10 degrees
47
what does 24-2 central visual field mean?
24 degrees
48
what does 30-2 central mean ?
central 30 degrees
49
which degrees does full threshold measure?
10-2 24-2 30-2
50
which degree does SITA measure?
SITA ( 10-2, 24-2. 30-2)
51
which degree does ZATA measure?
ZATA ( 10-2, 24-2)
52
which full threshold can measure centre and peripheral visual field?
SITA
53
which full threshold can not measure peripheral visual field?
ZATA
54
what is the advantage of FULL threshold?
:enables statistical analysis : provides diagnostic information : can monitor visual field progression : provides information about the reliability of the data
55
what is the disadvantage of FULL threshold?
: generally more time consuming than supra threshold | : although newer threshold procedures offer a comparable examination time
56
Which test can be used for driving?
Estermann visual field test
57
How does Estermann VF work>?
binocular both eyes | no trail lenses required. if px has glasses can wear them
58
what does the estermann VF test do?
used to ascertain whether fit to drive
59
what does amsler chart test used for?
used to measure central ten degrees of macula
60
how do you use amsler chart?
ask px if any of the lines are missing or distored
61
what distance do you use the amsler chart?
test isdesigned for 28-32cm so the patient should be corrected for the distance
62
which visual field test do you think you might choose for a 80 year old px who has senile dementia and nil pathology?
Supra threshold single stimulus
63
which visual field tests are more commonly used in an ophthalmology clinic?
SITA standard | SITA fast
64
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?
supra threshold multiple stimulus
65
which visual field test might you suggest to use on a 60 year old with advanced glaucoma ?
full threshold 24-2
66
if you have nil pathology which test should you use?
suprathreshold : multiple stimulus 68 points ( henson ) : single stimulus 68 points ( henson ) : c-76 quantify (Humphrey )
67
if you have pathology what do you use?
SITA 24-2 fast - henson ZATA 24-4 fast -humphrey smaller or larger field size based on pathology
68
if px have nil pathology however risk factor ( Disc , IOP, FOH)
consider SITA ZATA
69
What would you do to see macula problem?
Amsler test chart

clinical skills (13 decks)

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