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Glaucoma > Lecture 10: Electrodiagnostic Testing: ERG & VEP > Flashcards

Lecture 10: Electrodiagnostic Testing: ERG & VEP Flashcards

1
Q

what is a full field ERG? What are the 3 types of ERG

A
  • mass response of the entire retina for rod or cone systems
  • Photophic negative response (PhNR) - evaluates ganglion cell function
  • Pattern ERG (pERG) - evaluates ganglion cell function
  • Multifocal ERG (mfERG) - provides topographic mapping of central retina and function of cone system
  • mass electrical repsonse of the retina to luminance stimulation
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2
Q

What are the 2 main components of ERG?

A
  • Scotopic (dark adapted response)
  • Photopic (light adapted response)
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3
Q

What is visual evoked potential (VEP)?

A
  • function of primary visual pathway at cortical level
    • mfVEP
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4
Q

What is EOG?

A
  • electrooculogram - RPE function
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5
Q

What are the 4 types of diopsy vision testing system and what do each of them assess for?

A
  • ffERG - objectively evaluate cone & ganglion cell function
  • mfERG - objectivley evaluating localized retinal function
  • PERG - objectively evaluating ganglion cell function
  • VEP - Protocols for objectively evaluating the function of the entire visual pathway
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6
Q

Scotopic response: first positive b-wave noted is a pure __ response

A

ROD

(Scotopic response)

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7
Q

Max response to first stimulation is most important in determining between ___ and ___ pathology

A

photoreceptors, inner layer pathology

(scotopic response)

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8
Q

Negative a-wave assesses what?

A

photoreceptor function

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9
Q

Postive b-wave assesses what?

A
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10
Q

Photopic response: negative a-wave assesses what?

A

cone photoreceptors

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11
Q

Scotopic response: Positive b-wave inner retinal function

A
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12
Q

__ suppressed by flicker in photopic response

A

rods

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13
Q

Negative a wave = ____ ; Negative b wave = _____ & _____

A
  • photoreceptor response
  • bipolar & mueller cells
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14
Q

Oscillatory Potentials (OP)

A
  • ​Inner retinal currents from amacrine cells
  • Low amplitude wavelets superimposed on ascending B-wave
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15
Q

What is PhNR? (Photopic negative response)

A
  • slow negative component of B-wave of the CONE driven ffERG
  • Originates from ganglion cell activity
  • depends on intact RGC function
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16
Q

Modest correlation between amplitude of PhNR & thickness of… ? (2)

A
  • peripapillary RNFL
  • Ganglion cell layer thickness within the macula
17
Q

Pattern ERG is generated by the ___ and shows ____.

A

macula; spatial frequency selectivity

18
Q

Pattern ERG - retinal response what stimulus?

A

structured stimulus - reversing black/white checkboard grating

19
Q

pattern ERG should always be read with ___ or __

A

ffERG or VEP

20
Q

Pattern ERG is affected by diseased confined to the __

A

macula

  • will be normal in sever ROD-cone dystrophy with good central VA
  • May diagnose diseases that affect only the macula
21
Q

___ is considered to be one of the best electrodiagnostic tolls for assessment of RGC function

22
Q

PERG provides a functional evaluation of the retina __ __ function and __ __ function.

A

macular cone; ganglion cell

23
Q

What are the 3 components of pattern ERG?

A
  • Negative (N35)
  • Positive (P50)
    • Some RGC component
  • Negative (N95)
    • Large RGC component
24
Q

Which one is normal and which one is abnormal PERG?

A

Top normal

  • there are glaucoma patients who have abnormal ERG
    • P95 amplitude reduction is most significant
26
Q

In monkeys with bilateral optic atrophy and loss of central RGCs (green trace), the PERG, particularly the
__ component, is substantially reduced while the full-field flash ERG remains normal.

27
Q

What is mfERG

A
  • Provides topographic mapping of the central retinal function for the cone system
  • Diameter of 40-50 degrees
  • Allows detection of focal changes in retinal function
28
Q

mfERG: Amplitude and implicit time of the __component are most commonly used for analysis

29
Q

Pattern Visual Evoked Potential (pVEP) waveform components include what? (3)

A
  • N75
  • P100
    • Delay of latency of P100 indicates ON dysfunction involving axon (neuritis or demyelination)
    • Decrease in amplitude of P100 is usually due to atrophic changes
  • N135
  • Changes to the pVEP allow clinicians to place defect at the optic nerve, but it is very general
    • We need more specifics for glaucoma… e.g. location within the optic nerve
30
Q

Complete the chart

31
Q

Drawback of electrodiagnostic testing

A
  • Some tests are invasive (require electrodes on eye and eyelids)
  • Some tests are long (45 to 50 minutes)
  • Require consistent protocols and expert interpretation

Glaucoma (11 decks)

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