The Electro-retinogram Flashcards
what is the electro-retinogram used to show
it is a clinical test of vision which shows whats wrong with the retina, is a functional test of retinal function
which retinal cells does the electroretinogram specifically look at
photoreceptors bipolar cells amacrine cells RPE cells ganglion cells & interactions within the retina or the macula
what shapes the electrical signals recorded within the eye
electrical changes within the cells as a single photo transduction passes through the retina
from the sclera to the vitreous list the origins of electroretinogram responses
- 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)
what does the c-wave not record
the apical hyperpolarisation which comes from RPE cells
what is the a-wave a hyper polarisation of
photoreceptors
what is the b-wave a combination of
on & off bipolar cell activity & some contribution from muller cells
what are oscillatory potentials largely in nature
amacrine cells
what is the pattern ERG derived from
ganglion cell layer
what are photopic negative response PhNR responses of
the cone system
what are the photopic negative response PhNR responses shaped by
amacrine cells & off bipolar pathway
when do you record the scotopic threshold response STR
after being dark adapted for 3-4 days
what receptors are the on bipolar cells exclusively
MGLUR-R6 glutamate receptors
what blockers are the on bipolar cells exclusively
MNDA
what receptors are there within the off bipolar cell pathway
ionotropic receptors
what are the ionptropic receptors fast in
acting
what are the inotropic receptors expressed largely in
off bipolar cells
what do the inotropic receptors shape
the off bipolar cell pathway
which receptors of the off bipolar cell are linked and associated with autism
Glu6 or GRIK glutamte receptor
which wave is the hyper polarisation of bipolar cells
a-wave
what is the b-wave, depolarisation of
bipolar cells
what does the peak of an a-wave show in ERG waveforms as an all scotopic series in photopic conditions
cone responses at a faster frequency
what does the peak of a b-wave show in the ERG waveforms as an all scotopic series in photopic conditions
pure cone response which is smaller than the rod response
what happens to the b-wave if you increase the intensity higher
rising edge with ripples
what happens to the a-wave and b-wave if you increase the intensity higher
a-wave gets larger and b-wave gets smaller
what happens to the a-wave and b-wave as you increase light levels but still in scotopic conditions
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
