The Electro-retinogram

Question 1

what is the electro-retinogram used to show

Answer 1

it is a clinical test of vision which shows whats wrong with the retina, is a functional test of retinal function

Question 2

which retinal cells does the electroretinogram specifically look at

Answer 2

photoreceptors 
bipolar cells
amacrine cells
RPE cells 
ganglion cells & 
interactions within the retina or the macula

Question 3

what shapes the electrical signals recorded within the eye

Answer 3

electrical changes within the cells as a single photo transduction passes through the retina

Question 4

from the sclera to the vitreous list the origins of electroretinogram responses

Answer 4

• standing potential EOG light peak
  c-wave (doesn’t record the apical hyperpolarisation which comes from RPE cells)
• ERG a-wave (hyper polarisation of photoreceptors)
• ERG b-wave (combination of on & off bipolar cell activity & some contribution from muller cells)
  oscillatory potentials (largly amacrine cells in nature)
  pattern ERG (derived from ganglion cell layer)
  photopic negative response, PhNR (responses of the cone system & is shaped by amacrine cells & off bipolar pathway)
  scotopic threshold response STR (something you record after being dark adapted for 3-4 days)

Question 5

what does the c-wave not record

Answer 5

the apical hyperpolarisation which comes from RPE cells

Question 6

what is the a-wave a hyper polarisation of

Answer 6

photoreceptors

Question 7

what is the b-wave a combination of

Answer 7

on & off bipolar cell activity & some contribution from muller cells

Question 8

what are oscillatory potentials largely in nature

Answer 8

amacrine cells

Question 9

what is the pattern ERG derived from

Answer 9

ganglion cell layer

Question 10

what are photopic negative response PhNR responses of

Answer 10

the cone system

Question 11

what are the photopic negative response PhNR responses shaped by

Answer 11

amacrine cells & off bipolar pathway

Question 12

when do you record the scotopic threshold response STR

Answer 12

after being dark adapted for 3-4 days

Question 13

what receptors are the on bipolar cells exclusively

Answer 13

MGLUR-R6 glutamate receptors

Question 14

what blockers are the on bipolar cells exclusively

Answer 14

MNDA

Question 15

what receptors are there within the off bipolar cell pathway

Answer 15

ionotropic receptors

Question 16

what are the ionptropic receptors fast in

Answer 16

acting

Question 17

what are the inotropic receptors expressed largely in

Answer 17

off bipolar cells

Question 18

what do the inotropic receptors shape

Answer 18

the off bipolar cell pathway

Question 19

which receptors of the off bipolar cell are linked and associated with autism

Answer 19

Glu6 or GRIK glutamte receptor

Question 20

which wave is the hyper polarisation of bipolar cells

Answer 20

a-wave

Question 21

what is the b-wave, depolarisation of

Answer 21

bipolar cells

Question 22

what does the peak of an a-wave show in ERG waveforms as an all scotopic series in photopic conditions

Answer 22

cone responses at a faster frequency

Question 23

what does the peak of a b-wave show in the ERG waveforms as an all scotopic series in photopic conditions

Answer 23

pure cone response which is smaller than the rod response

Question 24

what happens to the b-wave if you increase the intensity higher

Answer 24

rising edge with ripples

Question 25

what happens to the a-wave and b-wave if you increase the intensity higher

Answer 25

a-wave gets larger and b-wave gets smaller

Question 26

what happens to the a-wave and b-wave as you increase light levels but still in scotopic conditions

Answer 26

the a-wave and b-wave is there but with reduced amplitude, there is a mix of rod a-wave and cone a-wave and contribution to b-wave is less