1. ELECTROPHYSIOLOGY
Presenter : Dr Ruchika Dhir (1st year resident)
Moderator : Dr Pushkar Dhir
DHIR HOSPITAL AND POSTGRADUATE INSTITUTE
OF OPHTHALMOLOGY
3. TYPES OF ERG
BASED ON ZONE OF STIMULUS
• FULL FIELD ERG/FLASH
• PATTERN ERG
• MULTIFOCAL ERG
BASED ON TYPE OF STIMULUS
•SINGLE FLASH
•FLICKER FLASH
•RED FLASH
•BLUE FILTER FLASH
•PATTERN ERG
BASED ON STATE ADAPTATION
•SCOTOPIC
•PHOTOPIC
•MESOPIC
9. ELECTRODES
ACTIVE ELECTRODES
• POSITIVE INPUT
• PLACED ON AREA OF INTEREST
REFERENCE ELECTRODE
• NEGATIVE INPUT
• PLACED AT ORBITAL RIM IPSILATERALY
GROUND ELECTRODE
• CONNECTED RECORDING SYSTEM
• FOREHEAD, EARLOBE,MASTOID
ACTIVE
ELECTRODE
NON CONTACT
CONJUNCTIVAL SKIN
CONTACT
CORNEAL
11. CONJUNCTIVAL ELECTRODE
DTL ELECTRODE
•ADVANTAGE
•EASY TO USE
•DISADVANTAGE
•BREAKS VERY OFTEN
HK LOOP
•EASY TO USE AND REUSABLE
DTL PLUS ELECTRODE
•HAS BETTER STRENGTH
GOLD FOIL ELECTRODE
•ADVANTAGE
•EASY & REUSABLE
•DISADVANTAGE
•DIFFICULT TO STERLIZE
13. PATIENT PREPARATION (ISCEV PROTOCOLS)
• MYDRIASIS
• AVOID STRONG ILLUMINATING PROCEDURE BEFORE ERG
• 30 MIN RECOVERY TIME BEFORE
SCOTOPIC (DA ERG)
20MIN OF DARK ADAPTATION IS REQUIRED
PHOTOPIC (LA ERG)
10 MIN OF LIGHT ADAPTATION IS REQUIRED
14. ISCEV PROTOCOLS
• SIX STANDARD PROTOCOLS
• NAMED ACCORDING TO DA, LA, FLASH STRENGTH
1. DA 0.01 ERG
2. DA 3 ERG
3. DA 10 ERG
4. DA OP’s
5. LA 3 ERG
6. LA 30 Hz ERG (FLICKER ERG)
SCOTOPIC ERG
23. VEP
• RECORD OF ELECTRICAL ACTIVITY GENERATED BY VISUAL STIMULUS MEASURED
AT VISUAL CORTEX
• DEPENDENT ON MACULA AS THESE FIBRES PRINCIPALLY PROJECT TO VISUAL
CORTEX
ERG REPRESENTS SUMMATED ACTIVITY OF RETINA IN RESPONSE TO LIGHT FLASH
ORIENTATION OF CELLS RADIAL, HORIZONTAL CELLS
ELECTRICAL RESPONSE TRAVEL FROM PHOTORECEPTOR TO GANGLION CELLS
NORMAL WAVEFORM
DIFFERENT WAVEFORM IN DIFFERENT CONDITION AND IN DIFFERENT PROTOCOLS
MOSTLY 2 WAVE SO BIPHASIC
TIME TAKEN TO INITIATE FROM TIME TO STIMULATION
New handheld RETeval system. (A) The recording system consists of handheld stimulator, recording and analysis device (a), a joint base (b), a soft patch that contacts the bony area around the eyes (c) and a disposable skin electrode array (d). (B) The centre of the dome structure features a red fixation point (red arrows), and participants were asked to focus on that point during the ERG recording. (C) Acquisition process. (D) A skin electrode array (LKC Technologies, Inc.) was placed on the orbital margin 2 mm from the lower eyelid margin. (E) The electrode array comprises three electrodes, a positive electrode, a negative electrode and a ground electrode, each of which is covered with tape
THIS IS AN EXTINGUISHED ERG CAN BE DUE TO
ADVANCED RP
LEBER CONGENITAL AMAUROSIS
TOTAL RD
OPTHALMIC ARTERY OCLUSION
LONG STANDING SIDEROSIS
CONE DYSTROPHY ASSOCIATED FEATURES
PHOTOAVERSION (HEMARLOPIA)
NYSTAGMUS
IMPAIRED COLOR VISION
LEFT EYE INNER RETINAL DYSFUNCTION
ISCHEMIC CRVO
ADVANCED DR
CHLOROQUINE, ETHAMBUTOL TOXICITY
SCREENING OF X LINKED CARRIERS (UNAFFECTED MEMBERS)
ABNORMAL VEP CAN BE BCOZ OF
1. DEFECT IN MACULA,OPTIC NERVE,OPTIC TRACT,OPTIC RADIATION & VISUAL CORTEX
