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Perception Exam 3 > ERG and VEP > Flashcards

ERG and VEP Flashcards

1
Q

What kind of ERG would you use for plaquenil retinopathy and what would you see? What kind of VF could you use?

A

Plaquenil retinopathy looks for damage of outer retina
Use mfERG
ERG would look like Mt St Helens
Could also use 10-2 visual field

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2
Q

What kind of ERG would you use for Glaucoma? What’s the most common tool for seeing structure abnormalities in glaucoma?

A

Glaucoma affects ganglion cells. Use pERG.

Commonly use OCT for structure

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3
Q

What else can you visualize with ERG?

A 
Glaucoma
Plaquenil retinopathy
Siderosis Bulbi
Genetic defects in children
Differentiate RP and CSNB
     RP has flatter ERG curve
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4
Q

What diseases would you expect to see only a sandcastle tiny peak in ERG (with periphery black)

A

Tiny sandcastle is caused by being mostly blind. Maybe some tunnel vision
Glaucoma, RP, CSNB, other genetic disorders causing blindness

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5
Q

What diseases would you expect to see lopped off Mt St Helens

A

Macula affected but periphery may still work
Plaquenil retinopathy
ARMD and Stargardt’s
Macular hole

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6
Q

What might you notice on a gross level in a child with Leber’s Congenital amaurosis?

A

Gaze disorder

No response to Teller Cards

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7
Q

Stages of Leber’s Congenital amaurosis?

A

Mild: Looks pretty normal
Moderate: Scleral window over macula
Severe: Widening of window and buildup of pigment around it - might look like RP

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8
Q

What tests could you use on LCA? (2)

A

ERG: Will be flatline at early age
Fluoroscein: Salt and pepper fundus

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9
Q

What do visually evoked potentials (VEPs) measure?

A

Objective VAs

How cortex responds to visual stimuli

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10
Q

What structures do VEPs measure?

A

Activity of cells in visual cortex
Usually V1
2/3 of cells for fovea

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11
Q

What stimuli do you use for VEPs?

A 
Anything that changes
Pattern
Luminance
Color
Most common reverse phase checkerboard
Decreases in size/VAs
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12
Q

Why would you use a phase reversing checkerboard to get VEPs

A

Want to stimulate simple cells
Can’t be held steady or not as much stimulation
Flickers

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13
Q

VEP vs ERG. Tell me what would happen with a full retinal stimulus, peripheral stimulus and foveal stimulus

A

Full retinal: Equal VEP and ERG
Foveal: VEP same as full retinal, ERG is reduced
Again, VEP focuses on V1 which is 2/3 foveal
Peripheral: VEP almost flatlines ERG is same as foveal

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14
Q

In mV, what’s the amplitude of brain noise?

A

60mV

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15
Q

What voltage does EOG measure?

A

6mV

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16
Q

What voltage does ERG measure?

A

1mV

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17
Q

How do you separate background noise in VEP?

A

To separate background noise, consider that VEP signals take 80ms to get through optic nerve to cortex. Filter out noise of EEG. Zeroes it out to allow you to see VEP

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18
Q

Stimuli for flash (AKA transient) VEP?

A

Alternating Black an white square separated by 250ms. Luminance is constant but pattern changes

19
Q

Who would you use a flash (AKA transient) VEP on?

A

Babies that may not respond to visual stimuli but do respond to auditory stimuli
See of optic nerve works

20
Q

What are you looking when analyzing results of a VEP?

A

Amplitude and latency

21
Q

What stimulus does a steady state (AKA Flicker) VEP use? At what CFF?

A

Phase reversing checkerboard flashing at 20 Hz

Similar to pERG

22
Q

Which is more accurate, the transient/flash VEP or the flicker/steady state VEP?

A

Flicker/Steady state VEP

23
Q

What’s the advantage of multifocal VEP?

A

Multifocal VEP can measure threshold contrast and also looks at multiple retinal loci

Compare to mfERG which also looks at multiple points on the retina

24
Q

How would you find threshold contrast with multifocal VEP?

A

Start at high contrast and go lower. Plot on graph with VEP amplitude on y and contrast on x. Extrapolate your resultant line down to the X intercept

25
Q

What can you do to enhance mfVEP?

A

Conscious attention

26
Q

What does wave that results from VEP look like?

A

3 dips and 3 peaks starting with a dip.

27
Q

What can the VEP assess (5)

A

Foveal patency

28
Q

Why is VEP best for Foveal patency?

A

VEP looks at visual cortex signals, most of which are from the fovea (2/3)

29
Q

What can cause decrease in foveal patency

A

Cortical blindness, Cataracts, during surgery

30
Q

How would you set up a patient to be tested for Optic nerve conduction with a VEP

A

Put patient in Ganzfeld with red bowl. Increased latency = demyelination

With MS, long latency even during remission

31
Q

How would you be able to tell that there was poor conduction in the optic nerve using a VEP?

A

Long latency

32
Q

What visual field defect would you notice in Leber’s optic neuropathy?

A

Size of normal scotoma will be enlarged

33
Q

What does acute Leber’s look like on the optic nerve?

A

Papilledema

34
Q

What does chronic leber’s optic neruopathy look like?

A

Pallor

35
Q

According to Kollner’s rule, what color defect would you get in Leber’s optic neuropathy?

A

Red/Green

Same as MS because ON affected

36
Q

What would you analyze on VEP graph to determine the refractive error

A

Amplitude

37
Q

Why would you use VEP to assess refractive error in babies?

A

See if glasses would help infant

38
Q

When do babies have 20/20 VEP potential?

A

6 months

39
Q

What’s the problem with measuring VEP in babies?

A

OVERESTIMATES their potential

40
Q

How much greater is VEP due to binocular summation?

A

1.4x

41
Q

When would binocular VEP be greater or less than what you’d expect?

A 
Less = Poor binocularity = amblyopia
More = abnormal crossing at chiasm = albinism
42
Q

How would you differentiate amblyopia and a retinal defect?

A

Retinal defect would show abnormal ERGs and VEPs

Amblyopia would show normal ERGs but abnormal VEPs

43
Q

What stream does VEP predominantly look at? Why would this be a problem?

A

Parvo. Might miss magno stuff - like glaucoma.

Perception Exam 3 (5 decks)

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