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ERG Flashcards

1
Q

what are the key elements of ERG testing?

A
  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
Q

which cells contribute more to te ERG signal?

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

LESS signal from horizontaly horiented:

  • horizontal
  • amacrine
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3
Q

which are the ON & OFF cells?

A
  • 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.
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4
Q

do skin electrodes yield same effect as Burian-Allen?

A

No,

skin electrodes yield smaller signals

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5
Q

where to place the REFERENCE electrode?

A
  • for monopolar recording:
    • in the temple
  • for bipolar recording
    • under the eyelids
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6
Q

factors that influence ERG signal

A
  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
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7
Q

what is the benefit of having ISCEV standards? whta is the meaning of ISCEV?

A
  • 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
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8
Q

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

THE 6 responses are the MINIMUM

A

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
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9
Q

what is the diameter of the ganzfeld stimulator?

and what is the type of light bulb?

A

40 cm

xenon light bulb placed at the top

gives DIFFUSE and homogeneous light to entire retina

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10
Q

what originates the Oscillatory potentials?

A

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

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11
Q

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

A

13: to 1 the rods win

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12
Q

what percentage of the cones is given by the cones?

A

25%

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13
Q

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

A

1:1

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14
Q

how many RODS and cones are there in the retina?

A

100 million RODS

6 million cones

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15
Q

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

A
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16
Q
A
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17
Q

how do the following curves look?

  1. rod
  2. mixed
  3. cone
  4. 30-Hz flicker
18
Q

what is this normal curve?

19
Q

what is this normal curve?

A

mixed or comibed

20
Q

what is this normal curve?

A

cone flicker

21
Q

what is this normal curve?

22
Q

what is a LED light?

A

light emmitting diode

23
Q

what is the structure of a contact lens electrode such as

Burian-Allen?

A

contact lens of PPMA

24
Q

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?

A

the baby has reduced amplitudes

25
Q

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

A
  • in RESTING
    • they are DEPOLARIZED
    • constant influx of Glutamine
    • photoreceptors golosos
  • after light stimulus
    • they HYPERPOLARIZE
    • lees glutamate
26
Q

how mny bipolar cells are conected to a photoreceptor and how are they called?

A

2 bipolar cells

the on bipolar and the off-bipolar

each will stimulate an on-center and an off center

27
Q

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

what is its function?

A

its GLUTAMATE

has an inhibitory funciton on BPC

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

28
Q

how does the on & off sytem works?

29
Q

what is the d-wave?

A

the off responses

30
Q

rods connect to what type of BPC?

cones to what type?

31
Q

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

how about the rods?

A

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
Q

what is the off-on ERG?

A
  • it uses photopic short and long duration flashes
    • a:wave from
      • photoreceptors
      • hyperpolarized BPC
    • b-wave
      • interation of H-BPC and D-BPC
33
Q

how do you get a d-wave and what is the significance of it?

A

d wave is off response

obtained using long duration flashes

usefull in CSNB where you don’t have the b-wave

34
Q

what are oscillatory potentials?

A

waves superimposed to the ascending slope of b-wave

35
Q

when was multifocal ERG invented?

A

in 1992

by Sutter and Tan

36
Q

how many hexagons are there in mf-ERG?

37
Q

classic ERG on ESCS?

38
Q

classice ERG for

KCNV2

39
Q

what is the pattern ERG useful for?

A

to check GCL

blakc & white checkerboard

N35, P50, N95

N95= GCL

P50= bipolars mostly some GCL

Genetics Fellowship (22 decks)

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