Takes into account magnitude and phase variability throughout the waveform recording - a recording that us in phase throughout the test will produce a magD value close to that of magnitude - a recording that is out of phase through the recording will produce a MagD value significantly less than that of mag

- recorded at inion - signal averaged - rewuries visual attention - uses constant luminance pattern - cortical problems manifest as amplitude reactions and or latency increases

Visual And Ocular Electrodiagnostics II Flashcards by Sarah Heath

Do you ever to electrodiagnosis all by itself?

It’s always just a piece of the puzzle to help in diagnosis or management

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Most basic

EOG

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Full-field electro-retinogram (ffERG)

Ganz feld

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PERG

Grating pattern of lines with pattern reversal, no net luminance change

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Difference between the VEP and pERG

VEP measures at the visual cortex, pERG measures at the retina

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Which tests measure a very big response

EOG
ECG
ERG

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Which tests use signal averaging to find the target voltage and why

Because its so small

pERG
VEP
mfERG

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A wave

Photoreceptors

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B wave

Bipolar cells

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Why is B wave so large

Bipolar cells have small potential, but the mueller cells which are glial absorb all of the electrolytes when they are released from the retina. Most of the B wave is not processing the info, just a depolarization effects

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What did we do in the pERG lab

30Hz flicker

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Wat is the best electrode for ERG?

Hansen Burian

-contact lens on the cornea

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Basic recording rewuries

Proper electrode placemtn
Excellent electrode contact
Signal averaging for all voltage potentials

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Magnitude D on pERG

Takes into account magnitude and phase variability throughout the waveform recording

a recording that us in phase throughout the test will produce a magD value close to that of magnitude
a recording that is out of phase through the recording will produce a MagD value significantly less than that of mag

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What drug can be monitored with pERG

Plaquenil

-plaquenil maculopathy

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What field would you expect a plaquenil to show loss in on pERG/

24 degrees

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Objectively measure the functional responses of the entire visual pathway from the anterior segment of the eye to the visual cortex

VEP

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What is the VEP measuring

How much energy is reaching the visual cortex and how long is it taking there

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Visual cortex area 17

Most organized visual reception in Cortex

-macular fibers are highly represented magnifying dramatically the visual impact of macular and fovea vision

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Cortical magnification

The macula is represented in a larger area in the cortical areas vs the rest of the retina
-where VEP picks up

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N75-P100-N135 complex in VEP

Time latency is measured in ms 
Amplitude is measures in microvolts 
-N=negative
-P=positive
-time= the time it occurred

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Where is VEP recorded

Inion

-bump on back of skull

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Recording VEP

recorded at inion
signal averaged
rewuries visual attention
uses constant luminance pattern
cortical problems manifest as amplitude reactions and or latency increases

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If not refracted properly and the targets are blurred in VEP

Low amplitude

Same latency

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How does amblyopia look on VEP

Notice the decrease in amplitude and the delayed response int he left eye

Multiple sclerosis and VEP

Extreme delay in response

Sweep VEP

Series of different grating sizes quieckly and rely on fact that you have a young healthy system with an infant - infants - rewuries visual attentions - estimates high spatial frequency cut off

Mf ERG

- presents local luminance shifts (flashes) - records responses by separation in time - providers focal outer layer ERG - requires signal averaging - requires best fixation

Where is the highest amplitude of ERG in the mfERG

Macula

Chloroquine toxicity

Produces central vision loss from an outer retinal thinning causing a characteristic bulls eye maculopathy -hydroxychloroquine used in arthritis is less toxic but is still monitored regularly

Chloroquine toxicity increases when

Size of dose and duration of therapy

MfERG ring ratios

Used for hydroxychloroquine toxicity - plot the sensitivities in a honeycomb pattern - comparing the central peak to zones in the paracentral to look for a shift in a ratio between those to see if you are losing paracentral sensitivity

Stimulus for EOG

Adaptation

Magnitude for EOG

6mV

Tissue for EOG

RPE

Components of EOG

Arden ratio

Signal average for EOG?

FfERG (Flash) stimulus

Ganzfeld flash

FfERg (Flash) magnitude

1mV

Tissue for ffERG (flash)

Photoreceptor Bipolar/mueller Ganglion cell

Signal average for ffERG (flash)?

Components of ffERG (flash)?

A-wave B-wave Oscillatory pot

FfERG (flicker) stimulus

Ganzfeld flash

Magnitude of ffERG flicker

1mV

Tissue for ffERG flicker

Cones

Components for ffERG flicker

Amplitude-phase

Signal average for ffERG flicker?

PERG stimulus

Pattern reversal

Magnitude for pERG

5uv

Tissue for pERG

Ganglion cell

Components of pERG

Amplitude and phase

Signal average for pERG?

Yes

Stimulus for mfERG

Multi focal flash pattern

Magnitude for mfERG

1uv

Tissue for mfERG

Macular function

Components of mfERG

Focal macular function

Signal average for mfERG?

Yes

VEP stimulus

Pattern reversal

Magnitude of VEP

5uV

Tissue of VEP

Visual cortex

Components for VEP

P-100 Amp/latency

Signal average in VEP?

Yes

MfVEP stimulus

Multi focal pattern reversal

Mgnirtude of mfvep

1uv

Tissue for mfVEP

Focal visual cortex

Components of mfVEP

Focal cortical function

Signal average for mfVEP?

Yes

Which of the following is thought to give rise to most of the large positive going potential seen in the B wave of the ff flash ERG?

Mueller Cells

Your 30 year old healthy patient with long standing acuity of 20/02 and 20/80 has no detectable disease and a normal ffERG but has a mild amplitude reduction and small latency delay in the high spatial frequency VEP (P100), occurring only on the OS potential. The OD VEP is normal. What os your diagnosis?

Amblyopia

Your patient is on hydroxychloroquine and is being monitored by you. He is 65 years old and has been on it for many years. Which LDX would most likely provide the most useful adjunct with other testing

MfERG | Possibly pERG, but not the number one test

Which of the following tests rewuries the most precise fixation b the patient?

MfERG

Which of the following conditions is frequently characterized by a nearly extinguished ffERG

RP | Non recordable ERGs early on

Your 35 year old patient has a long standing acuity loss bilaterally that has been getting worse and which is associated with a just noticeable appearance of granular pigmentation in both macular. She does not complain of night vision problems, there is a vague family history of relative “going blind” at a young age. You suspect cone dystrophy. Which of the following ELDX tests would provide you useful information supporting your diagnosis one way or another?

FfERG flicker Dark adapted ffERG PERG All of the above

Visual And Ocular Electrodiagnostics II Flashcards

(73 cards)