ERG

Question 1

what are the key elements of ERG testing?

Answer 1

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

Question 2

which cells contribute more to te ERG signal?

Answer 2

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

LESS signal from horizontaly horiented:

• horizontal
• amacrine

Question 3

which are the ON & OFF cells?

Answer 3

• 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.

Question 4

do skin electrodes yield same effect as Burian-Allen?

Answer 4

No,

skin electrodes yield smaller signals

Question 5

where to place the REFERENCE electrode?

Answer 5

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

Question 6

factors that influence ERG signal

Answer 6

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

Question 7

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

Answer 7

• 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

Question 8

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

THE 6 responses are the MINIMUM

Answer 8

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

Question 9

what is the diameter of the ganzfeld stimulator?

and what is the type of light bulb?

Answer 9

40 cm

xenon light bulb placed at the top

gives DIFFUSE and homogeneous light to entire retina

Question 10

what originates the Oscillatory potentials?

Answer 10

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

Question 11

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

Answer 11

13: to 1 the rods win

Question 12

what percentage of the cones is given by the cones?

Answer 12

25%

Question 13

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

Answer 13

1:1

Question 14

how many RODS and cones are there in the retina?

Answer 14

100 million RODS

6 million cones

Question 15

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

Answer 15

Question 17

how do the following curves look?

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

Answer 17

Question 18

what is this normal curve?

Answer 18

cones

Question 19

what is this normal curve?

Answer 19

mixed or comibed

Question 20

what is this normal curve?

Answer 20

cone flicker

Question 21

what is this normal curve?

Answer 21

rods

Question 22

what is a LED light?

Answer 22

light emmitting diode

Question 23

what is the structure of a contact lens electrode such as

Burian-Allen?

Answer 23

contact lens of PPMA

Question 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?

Answer 24

the baby has reduced amplitudes

Question 25

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

Answer 25

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

Question 26

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

Answer 26

2 bipolar cells the on bipolar and the off-bipolar each will stimulate an on-center and an off center

Question 27

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

Answer 27

its GLUTAMATE has an inhibitory funciton on BPC in the dark its constantly released to the BPC are constantly inhibited

Question 28

how does the on & off sytem works?

Answer 28

Question 29

what is the d-wave?

Answer 29

the off responses

Question 30

rods connect to what type of BPC? cones to what type?

Answer 30

Question 31

cones connect to on & off cells and then to on & off Ganglion cells how about the rods?

Answer 31

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**

Question 32

what is the off-on ERG?

Answer 32

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

Question 33

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

Answer 33

d wave is off response obtained using long duration flashes usefull in CSNB where you don't have the b-wave

Question 34

what are oscillatory potentials?

Answer 34

waves superimposed to the **ascending slope of b-wave**

Question 35

when was multifocal ERG invented?

Answer 35

in 1992 by Sutter and Tan

Question 36

how many hexagons are there in mf-ERG?

Answer 36

103

Question 37

classic ERG on ESCS?

Answer 37

Question 38

classice ERG for KCNV2

Answer 38

Question 39

what is the pattern ERG useful for?

Answer 39

to check GCL blakc & white checkerboard N35, P50, N95 N95= GCL P50= bipolars mostly some GCL