ERG-2 pathognomonic Flashcards
KCNV@ causes what disease?
cone dystrophy with SUPERnormal rod ERG
- gene encoding a potassium channel
- 1st or 2nd decade of life
- decreased vision (20/40 to LP)
- photophobia
- nyctalopia sometimes
- usually myopic
- Nystagmus is UNCOMMON
- color vision abn red-green axis
- NORMAL FUNDUS with late stages showing some macular changes
- normal FAF
- variable SDOCT (thinning, lucency, ez disruption) - looks like an ROP macula with normal pit but hin ONL
what could this be?
- possible cone dystrophy with SUPERNORMAL rod ERG
- KCNV2
- look at the macula perfoveal changes
- otherwise fundus is normal
- SDOCT looks like preme macualr with good pit but thinn ONL
- this patients have a wide range of vision and photophobia is classic
what could this be?
- cone dystrophy with supranormal rod ERG
- by KCNV2
what is PERG?
- is the retinal response
- to a black and white checkboard
- that is isoluminant
- has specific waves
- N35 : negative at 35 milliseconds
- P50: positive at 50 milliseconds — from Bipolar celss and some RGC
- N95: large negative wave at 95 millisecons —from RGC
- P50 depends in the healthyness of photoreceptors
what is this?
pattern ERG
- N35 : negative at 35 milliseconds
- P50: positive at 50 milliseconds — from Bipolar celss and some RGC
- N95: large negative wave at 95 millisecons —from RGC
- P50 depends in the healthyness of photoreceptors
how is the pattern ERG going to look in a cone dystrophy?
abnormal
because PERG is a measure of macular funciton
what are the classic ERG findings of KCNV2?
- DA 0.002 (super dim light: no response (in normals there is always a response)
- DA 0.01: delayed and reduced
- DA 3.0: its delayed but OK
- DA 11.0: supranormal giant b-wave!!!
- LA 3.0 and 30hz: delayed and reduced
how to test s-cones?
- with blue stimulus
- 445 nm
- 80 cd.2
- WITH an ORANGE background
- to saturate L and M cones
- 620 nm, 560 cd.m2
how to test ON & OFF ERG?
- LONG orange stimulus
- 200 milliseconds
- 620 nm
- 560 cd/m2
- GREEN background
- 530 nm
- 150 cd/m2
- The b-wave is the ON response
- the d-wave is the OFF response
what is this?
ESCS
what are the units of the flashes used in ERG?
candela-seconds / square meter
cd.s / m2
how much time is required for dark adaptation?
minimum 20 minutes
what is the difference between LA 3.0 and cone flicker?
- LA 3.0 uses 30 cd.s/m2
- cone flicker uses 30 cd.s / m2
- but the cone flicker flashes at 30 Hx (super fast not allowing the rods to recover)
*
how is light adaptation done?
- for 10 minutes
- patient in front of ganzfeld
- with a background of 30 cd.s / m2
- this background is mantained during the photopic testing
what info you get from the DA 0.01?
- you should see the positive b-wave
- its a response from the ON bipolar cells from
- the rod system
RODS to ON BPC
which are the cells originating the OPs?
the amacrine cells
if the DA 0.01 speaks of the ON-BPC rod system response….
what infor you get from DA 3.0?
is there a need for other DA flashes?
- the DA is not too useful
- because the a-wave in normals has a wide range of values
- so its difficult to tell if a response is delayed
- Recommend use DA 10.0 or DA 11.0
- this has a better defined 9-12 msecs awave peak
*
- this has a better defined 9-12 msecs awave peak
what info you get from cone flicker
and from the LA 3.0?
- the cone flicker is cone specific
- but arises from the inner retina
- evaluated the CONE SYSTEM
- including the BPC
- so its not specific within the cone system
- the LA 3.0
- a-wave comes from
- cones
- OFF-BPC
- b-wave from ON & OFF BPC
- a-wave comes from
how do ON & OFF cells work?
what happens to the cones with light stimulus
