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Glaucoma > Lec.5: Visual Fields > Flashcards

Lec.5: Visual Fields Flashcards

1
Q

in VF perimetry where does the blind spot sit?

A

15 degrees temporally

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2
Q

(T/F) nerve fibers from the superior retina cross over to the inferior retina and vice versa?

A

False (nerves respect the midline

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3
Q

what parameters detect a weak stimulus (dim light)?

A

low threshold and high sensitivity

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4
Q

what parameters detect a strong stimulus (bright light)?

A

high threshold and low sensitivity

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5
Q

in HFA II what is the distance between the eye and field of view?

A

30 cms

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6
Q

which phenomenon states that moving targets are more visible than non-moving targets?

A

Riddoch phenomenon

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7
Q

what happens to intensity as the decibel value increases?

A

higher the decibel value (40 dB) the lower the intensity of the stimulus

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8
Q

what represents the intensity that is just marginally visible (patient will perceive light 50% of the time)?

A

threshold

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9
Q

how is the isopter determined?

A

moving a stimuli from a region in the periphery where it is infra threshold to a region where it is supra threshold.

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10
Q

what are some reasons for using brighter light in VF testing?

A

testing peripheral retina, or testing damaged retinal tissue

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11
Q

what effect occurs when one fixates at a particular point and after about 20 secs a stimulus away from the fixation point (periphery) starts to fade and disappear?

A

troxlers effect

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12
Q

what is the gold standard in VF test?

A

24-2 SITA standard

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13
Q

in regards to reaction time, how does a SITA VF differ from older strategies?

A

speeds up test for fast responder and slows it down if responses are slower

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14
Q

what are the 3 types of catch trials detected by a VF machine?

A

false positive, false negative and fixation loss

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15
Q

what percentage of stimulus is presented in the Heijl-Krakau blind spot method?

A

5% of stimulus presented are used to check fixation

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16
Q

and what is the average size of that blindspot?

A

5 degrees wide by 7 degrees tall

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17
Q

what is it called when a patient responds when no stimulus is present?

A

false positive

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18
Q

what is it called when patients fails to recognize proportion of visible stimuli?

A

false negative

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19
Q

what the are acceptable SITA rates?

A
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20
Q

(T/F) Hippus affects VF results?

A

false

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21
Q

what size pupil needs to be dilated for a VF test?

A
22
Q

do you dilate patients with catarcts prior to running a VF?

A

yes

23
Q

what must always be entered before performing a VF test?

A

patient age and refractive error

24
Q

what are the type of defects that you can quickly identify in a grey scale image?

A

central, paracentral, nasal defects and blind spot

25
Q

are peripheral points of interest in a 30-2?

A

no, but they are in 24-2

26
Q

what raw data values would you expect to see centrally? and Peripherally?

A 
centrally= threshold of lower 30's dB
peripherally= threshold of upper 20's dB
27
Q

when examining the total deviation plot, what values can be viewed suspiciously?

A
28
Q

what does a p-value of 0.5% mean?

A

chance that they are normal is less than 0.5%

29
Q

how does fixation differ in octopus than in humphrey?

A

in octopus the machine detects a loss of fixation and stops projecting light (automated eye tracking)

30
Q

how do the humphrey and octopus machines indicate an area where light is not detected?

A 
humprey= assigns a zero value
octopus= assigns a black square
31
Q

how are defects represented in a humphrey and in an octopus reading?

A 
humphrey= negative value
octopus= will give you a positive number
32
Q

what global indices in HFA and octopus mean the same thing?

A

mean deviation= mean defect

pattern standard deviation= loss of variance

33
Q

when examining the pattern deviation what are the p-value criteria for a cluster of 3 or more points?

A

all must be depressed at a p

34
Q

can the 2-3 cluster points be in opposing hemifields?

A

NO, they must all be in the same hemifield

35
Q

when staging glaucoma based on a MD score: better than -6 dB

A

mild

36
Q

when staging glaucoma based on a MD score: worse than -6 dB but better than -12 dB

A

moderate

37
Q

when staging glaucoma based on a MD score: worse than -12 dB

A

severe

38
Q

when staging glaucoma based on the Brusini graph, what is plotted along the y-axis and what is plotted along the x-axis?

A

y-axis is PSD

x-axis is MD

39
Q

what classifications of defects does the Brusini graph allow you to identify?

A

localized defect, mixed defect or generalized defect

40
Q

in early glaucoma, does the VF defect tend to remain steady?

A

no it tends to fluctuate

41
Q

what represents a worse mean defect result in HFA?

A

negative number

42
Q

what correlates with a worse mean defect result in octopus?

A

larger (positive) number

43
Q

what may lead to errors during a VF test?

A

miosis, lens opacities, uncorrected refractive error, ptosis, inadequate adaptation, lenses too far way from the eye

44
Q

what is percentage of M cells?

A

10%

45
Q

what is the percentage of P cells?

A

80%

46
Q

what is the percentage of K cells?

A

9%

47
Q

what are the names of cells that make the magno system?

A

Parasol, Palpha, M or MC, phasic or broad band

48
Q

what are the names of cells that make the parvo system?

A

Midget, Pbeta, P or PC, tonic or color opponent

49
Q

what FDT (frequency doubling technology) screening test allows you to test functioning of M-cells?

A

low spatial frequency sinusoidal grating (greater spacing between the bars)

50
Q

what are the advantages of N-30-5 screening test?

A

only take 1 min 15 secs and has a 5% chance that a normal person has an error

Glaucoma (12 decks)

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