ERG-2 pathognomonic

Question 1

KCNV@ causes what disease?

Answer 1

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

Question 2

what could this be?

Answer 2

• 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

Question 3

what could this be?

Answer 3

• cone dystrophy with supranormal rod ERG
• by KCNV2

Question 4

what is PERG?

Answer 4

• 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

Question 5

what is this?

Answer 5

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

Question 6

how is the pattern ERG going to look in a cone dystrophy?

Answer 6

abnormal

because PERG is a measure of macular funciton

Question 7

what are the classic ERG findings of KCNV2?

Answer 7

• 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

Question 8

how to test s-cones?

Answer 8

• with blue stimulus
  
  • 445 nm
  • 80 cd.2
• WITH an ORANGE background
  
  • to saturate L and M cones
  • 620 nm, 560 cd.m2

Question 9

how to test ON & OFF ERG?

Answer 9

• 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

Question 10

what is this?

Answer 10

ESCS

Question 11

what are the units of the flashes used in ERG?

Answer 11

candela-seconds / square meter

cd.s / m2

Question 12

how much time is required for dark adaptation?

Answer 12

minimum 20 minutes

Question 13

what is the difference between LA 3.0 and cone flicker?

Answer 13

• 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)
  *

Question 14

how is light adaptation done?

Answer 14

• for 10 minutes
• patient in front of ganzfeld
• with a background of 30 cd.s / m2
  
  • this background is mantained during the photopic testing

Question 15

what info you get from the DA 0.01?

Answer 15

• you should see the positive b-wave
• its a response from the ON bipolar cells from
• the rod system

RODS to ON BPC

Question 16

which are the cells originating the OPs?

Answer 16

the amacrine cells

Question 17

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?

Answer 17

• 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
    *

Question 18

what info you get from cone flicker

and from the LA 3.0?

Answer 18

• 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

Question 19

how do ON & OFF cells work?

Answer 19

Question 20

what happens to the cones with light stimulus

Answer 20