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Flashcards in ERG Deck (40):
1

what are the key elements of ERG testing?

  1. Stimulator
    1. Ganzfeld bown - traditional
    2. light-emiting diode-based full-filed stimulator
  2. Electrodes
    1. Burian-Allen
    2. DTL fiber electrodes
  3. Computer to amplify signals and for analysis

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2

which cells contribute more to te ERG signal?

  • the radially oriented cells
    • photoreceptors 
    • bipolars
    • glia
    • RPE

LESS signal from horizontaly horiented:

  • horizontal
  • amacrine

3

which are the ON & OFF cells?

  • The CONE conect to:
    • bipolar cells of 2 types
      • ON : depolarizing
      • OFF: hyperpolarizing
  • Observe that 1 cone connects to 2 bipolar cells
  • 6 rods conect to one Red blood cells.

4

do skin electrodes yield same effect as Burian-Allen?

No,

skin electrodes yield smaller signals

5

where to place the REFERENCE electrode?

  • for monopolar recording:
    • in the temple
  • for bipolar recording
    • under the eyelids

6

factors that influence ERG signal

  1. type of electrodes:
    • skin electrode yields smaller signals
  2. stimulous conditions
    1. stength
    2. wavelegth (like the specific WL for cones
  3. background illumination
  4. duration of stimulous

7

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

8

whic are the 6 ERG protocols-responses by ISCEV in 2008

THE 6 responses are the MINIMUM

DARK ADAPTED x 30 mins

  1. DA 0.01 ERG  -24db  -3.9 log units
    •  (rod response on BipC)
  2. DA 3.0 ERG 0 db
    • combined rod and cone sytem on BipC
    • ROD DOMINATED
  3. DA 10 ERG  11 db
    • combined response ENHANCED a-waves
  4. DA Oscillatory potentials 0 db
    • responses from Amacrine cells

LIGHT ADAPTED x 10 mins (background illumination of 40cd/m2 suppress rod activity)

  1. 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
  2. LA ERG   11 db
  3. LA 30 Hz flicker ERG
    • sensitive cone-pathway driven response

9

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

10

what originates the Oscillatory potentials?

represent the inhibitory action of AMACRINE cells on the b-wave

11

how many more cones are there in comparison with the rods?

13: to 1 the rods win

12

what percentage of the cones is given by the cones?

25%

13

at the central fovea what if the cone:ganglion cell relation?

1:1 

14

how many RODS and cones are there in the retina?

100 million RODS

6 million cones

15

what is the distribution of cones and rods in the retina?

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16

17

how do the following curves look?

  1. rod
  2. mixed
  3. cone
  4. 30-Hz flicker

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18

what is this normal curve?

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cones

19

what is this normal curve?

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mixed or comibed

20

what is this normal curve?

cone flicker

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21

what is this normal curve?

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rods

22

what is a LED light?

light emmitting diode

23

what is the structure of a contact lens electrode such as 

Burian-Allen?

contact lens of PPMA

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24

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 

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25

what is the resting potential of the photoreceptors and what happens when they are exited by light?

  • in RESTING
    • they are DEPOLARIZED
    • constant influx of Glutamine
    • photoreceptors golosos
  • after light stimulus
    • they HYPERPOLARIZE
    • lees glutamate

26

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

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27

what is the main neurotransmitter in the rods-cone system? 

what is its function?

its GLUTAMATE

has an inhibitory funciton on BPC

in the dark its constantly released to the BPC are constantly inhibited

28

how does the on & off sytem works?

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29

what is the d-wave?

the off responses

30

rods connect to what type of BPC?

cones to what type?

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31

cones connect to on & off cells and then to on & off Ganglion cells

how about the rods?

the rods contact a bipolar depolarized cell

but DOES NOT contact the GC

it reaches the GC viat the on& off BPC via

the AMACRINE CELLS

so Rods are shy and only touch GC via Amacrines

32

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

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33

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

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34

what are oscillatory potentials?

waves superimposed to the ascending slope of b-wave

35

when was multifocal ERG invented?

in 1992 

by Sutter and Tan

36

how many hexagons are there in mf-ERG?

103

37

classic ERG on ESCS?

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38

classice ERG for

KCNV2

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39

what is the pattern ERG useful for?

to check GCL

blakc & white checkerboard

N35, P50, N95

N95= GCL

P50= bipolars mostly some GCL

40