ERG Flashcards
what are the key elements of ERG testing?
-
Stimulator
- Ganzfeld bown - traditional
- light-emiting diode-based full-filed stimulator
-
Electrodes
- Burian-Allen
- DTL fiber electrodes
- Computer to amplify signals and for analysis
which cells contribute more to te ERG signal?
- the radially oriented cells
- photoreceptors
- bipolars
- glia
- RPE
LESS signal from horizontaly horiented:
- horizontal
- amacrine
which are the ON & OFF cells?
- The CONE conect to:
- bipolar cells of 2 types
- ON : depolarizing
- OFF: hyperpolarizing
- bipolar cells of 2 types
- Observe that 1 cone connects to 2 bipolar cells
- 6 rods conect to one Red blood cells.
do skin electrodes yield same effect as Burian-Allen?
No,
skin electrodes yield smaller signals
where to place the REFERENCE electrode?
- for monopolar recording:
- in the temple
- for bipolar recording
- under the eyelids
factors that influence ERG signal
- type of electrodes:
- skin electrode yields smaller signals
- stimulous conditions
- stength
- wavelegth (like the specific WL for cones
- background illumination
- duration of stimulous
what is the benefit of having ISCEV standards? whta is the meaning of ISCEV?
- ISCEV =
- int soc for the Clinical Electrophysiology and Vision
- The standards were developed so ANY ERG recorded in any clinic around the world would be comparable
whic are the 6 ERG protocols-responses by ISCEV in 2008
THE 6 responses are the MINIMUM
DARK ADAPTED x 30 mins
-
DA 0.01 ERG -24db -3.9 log units
- (rod response on BipC)
-
DA 3.0 ERG 0 db
- combined rod and cone sytem on BipC
- ROD DOMINATED
-
DA 10 ERG 11 db
- combined response ENHANCED a-waves
-
DA Oscillatory potentials 0 db
- responses from Amacrine cells
LIGHT ADAPTED x 10 mins (background illumination of 40cd/m2 suppress rod activity)
-
LA 3 ERG 0 db – cone response
- responses from cone system
- a-wave comes from:
- cone OFF-BipC
- b-wave comes from:
- on & off BipC
- LA ERG 11 db
-
LA 30 Hz flicker ERG
- sensitive cone-pathway driven response
what is the diameter of the ganzfeld stimulator?
and what is the type of light bulb?
40 cm
xenon light bulb placed at the top
gives DIFFUSE and homogeneous light to entire retina
what originates the Oscillatory potentials?
represent the inhibitory action of AMACRINE cells on the b-wave
how many more cones are there in comparison with the rods?
13: to 1 the rods win
what percentage of the cones is given by the cones?
25%
at the central fovea what if the cone:ganglion cell relation?
1:1
how many RODS and cones are there in the retina?
100 million RODS
6 million cones
what is the distribution of cones and rods in the retina?
how do the following curves look?
- rod
- mixed
- cone
- 30-Hz flicker
what is this normal curve?
cones
what is this normal curve?
mixed or comibed
what is this normal curve?
cone flicker
what is this normal curve?
rods
what is the structure of a contact lens electrode such as
Burian-Allen?
contact lens of PPMA
what are the difference in waves of an ERG in an adult and an ERG in a 3 month-old baby if both are normal and done with Burrian-Allen method?
the baby has reduced amplitudes
how mny bipolar cells are conected to a photoreceptor and how are they called?
2 bipolar cells
the on bipolar and the off-bipolar
each will stimulate an on-center and an off center
how does the on & off sytem works?
rods connect to what type of BPC?
cones to what type?
what is the off-on ERG?
- it uses photopic short and long duration flashes
- a:wave from
- photoreceptors
- hyperpolarized BPC
- b-wave
- interation of H-BPC and D-BPC
- a:wave from
how do you get a d-wave and what is the significance of it?
d wave is off response
obtained using long duration flashes
usefull in CSNB where you don’t have the b-wave
classic ERG on ESCS?
classice ERG for
KCNV2
