vep for the 21st century
Post on 16-Jul-2015
111 Views
Preview:
TRANSCRIPT
VEP For The 21st CenturyJody Abrams, MD
Sarasota Retina Institute
Disclosures
I do neuro-ophthalmology so no financial
disclosures
I do refuse to wear a bowtie
We do own one of the VEP machines
VEP For The 21st Century
The SRI Update course baby
VEP For The 21st Century
VEP: visually evoked potential, visually evoked
response, and visually evoked cortical potential
Electrical impulse from the eye to the brain
Part of an EEG
VEP For The 21st Century
VEP For The 21st Century
Functional integrity of entire visual pathway
Anterior Segment to Visual Cortex
VEP For The 21st Century First noticed during strobe lights with early EEGs in
the 30s
Computers were able to extract the visual potentials with signal averaging
Similar to anti-radar jamming programs in the 50s
Saves defined time period of activity and averages out the randomness
VEP For The 21st Century
Electrical signal for VEP is 1-20 microvolts
Computer’s data acquisition is synchronized to the timing of the visual stimulus
Apply signal averaging to repeated stimuli and
the wave form is captured
VEP For The 21st Century
Pattern reversal stimulation is preferred testing
stimuli
Black and white checker board alternates
Light output remains the same
VEP response is from detection of edges between
the white and black areas
VEP For The 21st Century
First negative peak is N75
First positive peak is P100
Second negative peak is
N135
VEP For The 21st Century
Amplitude is amount of
energy reaching the
cortex
Difference between N75
and P100
Normal is around 6 microvolts for 32x32 board
VEP For The 21st Century
Amplitude gives how much information is making
it to the occipital lobe
Increase often can indicate better discrimination
Refraction can be a big issue with this
VEP For The 21st Century
Latency is the time it takes to get the information
back to the occipital lobe
P100 is peak of the information getting to the
visual cortex
Average is 100 ms (97-117)
VEP For The 21st Century
Latncy is increased by impedance in conduction
Less variation then amplitude
VEP For The 21st Century
Most common pattern is checkered board or
bars
Best response in normal patients at 32x32
pattern size
Adjust for level of vision
VEP For The 21st Century
Contrast is adjusted for cell bias
High contrast for parvocellular
Low contrast for magnocellular
VEP For The 21st Century
Parvocellular cells most
abundant
Sensitive to color
Help with discriminating fine
detail
VEP For The 21st Century
Magnocellular cells
Coarse vision
Motion
More sensitive with low contrast
Thought to be damaged in
early glaucoma
VEP For The 21st Century
Flash VEP good for extreme vision loss or if not
able to focus on screen
Look at N2 (90 ms) and P2 peaks (120ms)
VEP For The 21st Century
Machines used to be
complicated
Mostly reserved to
universities
VEP For The 21st Century
Computer advancements
More compact system
Easier tech work
Interpretation easier
VEP For The 21st Century
Now in ophthalmology offices, optometry
offices, and neurology clinics
Use has exploded
Need to at least know what it means
VEP For The 21st Century
VEP is a tool
Does not give the diagnosis
A “semi” objective way
to track change
VEP For The 21st Century
VEP ignores the appearance
It looks at how the system runs
VEP For The 21st Century
Amblyopia
Glaucoma
Traumatic Brain Injury
Optic Neuritis/MS
Other causes of optic nerve dysfunction
Functional visual loss
Dense cataracts
VEP For The 21st Century
55 y/o BF
Family hx of glaucoma
IOP 21/19
Corneal thickness 555/542
VEP For The 21st Century
Angles open
C/D 0.7 ou
VEP For The 21st Century
HVF normal OU
SD-RNFL 92 and 88
Would you treat?
VEP For The 21st Century 34 y/o obese WF
Headaches
Sent with dx of PTC
On Diamox 500 bid
Denies visual complaints
VEP For The 21st Century
VA 20/25 ou
Pupils no APD, no light/near disassociation, brisk
VEP For The 21st Century
Is it time to rush to OR for a nerve sheath
fenestration or VP shunt?
Can the Diamox be increased and watch
closely?
VEP For The 21st Century 32 WF
1 s/p delivery with eclampsia
Now has LP vision ou
Pupils brisk, no APD, no LND
CF unreliable
VEP For The 21st Century
-9 myopia ou
Tilted Optic nerves
OCTs show thinning but difficult scan secondary
to optic nerve anatomy
VEP For The 21st Century
Is this a real problem?
Refuses MRI
OB/GYN feels is faking it to get attention
Posterior reversible encephalopathy syndrome
VEP For The 21st Century
89 yo WM
Sent over for abnormal VF and VEP
Pt has not noticed visual change
Original fields appeared to have Left
homonymous hemianopia
This lead to MRI
which was read as
normal
A VEP was done
VEP For The 21st Century
Our Exam
20/25 ou
Pupils no APD, no L/N, brisk
Fundus showed Dry ARMD
RNFL
OD 103
OS 107
VEP does not give all the answers
Make sure getting good data
If it does not make sense with all the other
information repeat the test
CPT code 95930
top related