11 end me Flashcards
Types of electroretinograms:
Full field erg (ERG)
Pattern erg (PRG)
Multifocal erg (mfERG)
Electrooculogram (ROG)
Cortical visual evoked potential (VEP)
General function of DA-ERG
Recording of electric potentials from visual stimuli via electrodes on eye/orbit skin/scalp
Record following 20min dark adaptation, and given light strength (cd sm-2)
DA-ERG Flash strength and related retina cells:
0.01 cd sm-2 > Rod bipolar
(standard) 3.0 cd sm-2 > rod ON bipolar
10.0 cd sm-2 > rod ON bipolar
Expected wave showing in DA-ERG (full field ERG):
DA 0.01 > flat line > increase to 400uV > slow decrease
DA 3 > decrease to -350uV > increase to 350uv > decrease
DA 10 > decrease to -350uV > increase to 400uV > decrease
Oscillatory potentials > wibbles from amacrine signalling on rising limb of b-waves
DA 3 and 10 comparison:
DA 10 > larger A wave peak, shorter wavelength
General function of LA-ERG
Recording of electric potentials following 10min with 30 cd ms-2
LA ERG and related retina cells:
A-wave > Cone photoreceptors and OFF-bipolar cells
B-wave > Cone ON/OFF-bipolar cells
(Low B/A ratio > dysfunction)
VEP vs ERG:
ERG > retina response to stimuli
VEP > Signal transferal from retina
Pattern ERG related cells can recording:
Macula ganglion cells / cones
Time Pos 50 of PERG > peak amp.
Time Neg 95 of PVEP > Peak amp.
Multifocal ERG:
60-100 separate measurements over 45 degrees of macula
Electrooculogram:
RPE assessment via apical/basal potential difference
Provides assessment of RPE/photoreceptor complex
DDX via ERG:
Optic neuropathy > abnormal PVEP
Maculopathy > PERG P50 abnormal
Retinopathy > ERG abnormal
RP epitheliopathy (BEST) > ROG abnormal
Night blindness testing:
Full field ERG DA 3/10
Retinitis pigmentosa:
a-wave reduction and b-wave reduction > rod dysfunction
B-wave reduction, a-wave sparing > post phototransducion
Acquired causes of rapid VA loss
Carcinoma associated retinopathy (CAR)
Autoimmune retinopathy (AIR)
Vit A def.
CSNB ERG presentation:
Loss of ON-path, OFF-path preserved
DA ERG will have no increase
Decrease in A-wave (b/a ratio <1)
PERG readings:
Reduction of N95, preserved P50 > dysfunction at ganglion cell layer
Visual evoked potentials:
Recordings from scalp to measure visual pathway response
P100 component evaluates dysfunction post retina
Clinical presentation of melanoma-associated retinopathy:
Normal fundus, DA 0.01 ERG
Abnormal PERG, MfERG, DA 3/10 ERG, LA ERG
Similar response to complete CSNB
Retinitis pigmentosa clinical presentation:
Spicule formation, RPE atrophy
All ERG abnormal
Variable rod cone dystrophy
Genes in CSNB:
Complete: NYX, GRM, GPR179, TRPM1
Incomplete: CABP4
