This document discusses electrophysiological tests, specifically the electroretinogram (ERG). It provides details on: 1) The ERG records the electrical response of the retina to light stimuli and can help diagnose retinal diseases. It follows standardized protocols to ensure comparability between tests. 2) The ERG response consists of the a-wave from photoreceptors, b-wave from bipolar cells and Muller glia, and oscillatory potentials from amacrine cells. 3) The International Society for Clinical Electrophysiology of Vision standardized ERG protocols in 1989 to evaluate rod and cone function and detect inner retinal abnormalities.

1. Electrophysiological
tests
Presenter : Dr. Reshma Peter
Moderator : Dr. Prabhakar

2. Electrophysiological methods of examination involve the
recording of bioelectric potentials that arise during the
neural processing of visual information by the various
elements of the afferent visual pathways.
The various methods include
1.ERG (Electroretinogram)
 Ganzfeld full field
 Focal
 Pattern
 Multifocal
2.EOG (Electro-oculogram)
3.VEP/VER (Visual Evoked Potential/Response)
• Pattern
• Flash

3. International Society for Clinical
Electrophysiology of Vision (ISCEV)
Standardised the protocols for performing
electrophysiological tests (1989)
Ensures uniformity and comparability between labs

4. History
Du Bois-Raymond (1849)-1st discovered EOG
Frithiof Holmgren (1865)-1st recorded that alteration in
electric potential occurs when light is thrown on retina
Dewar (1877)- 1st recorded ERG In humans
Einthoven and Jolly (1908)-separated the ERG response
into 3 components: a-wave, b-wave and c-wave
Riggs(1941)-introduced practical recording contact lens
electrode in humans

5. Riggs (1954) and Francois (1956)worked extensively and
popularized EOG
 Arden & Fojas (1962)-discovered importance of ratio
Ragnar Granit (1967) demonstrated the physiology of th
e receptor potential of each component of the ERG- Nob
el prize winner
Sutter and Tran (1992)- developed multifocal ERG

6. Anatomy

10. ELECTRORETINOGRAM
 Response recorded by placing electrodes on the surface of eye
 The recorded response is weak and needs to be amplified
 Recorded data can be stored and analyzed on a computer
Recording of the electrical response of the retina
to light stimulus
which may be a flash of light or a light pattern
under different states of light adaptation

11. useful diagnostically in differentiating certain
retinal diseases
It is the composite of electrical activity from
the photoreceptors, Muller cells & RPE.

13. BASIC PRINCIPLE OF ERG
 Sudden illumination of retina.
 Simultaneous activation of all the retinal cells to generate the current
 Currents generated by all the retinal cells mix, then pass through
vitreous & extra cellular spaces.
 High RPE resistance prevents summated current from passing
posteriorly.
 The small portion of the summated current which escapes through
the cornea recorded as------------

14.  ‘b wave’ :
 ‘positive’ (upward) wave
 from bipolar cells and Muller
cells
 reflects bipolar cell activity.
 ‘Oscillatory potentials ‘:
 Small rippling currents
in b wave Ascending limb
 3 or more wavelets
 produced by Amacrine cells in
inner plexiform layer.
 ‘a wave’ :
 ‘negative’ (downward) wave
 Arises from photoreceptors
 reflects photoreceptor function
 Late receptor Potential

15.  ‘C wave ‘–
 Prolonged positive wave
 Low Amplitude
 Not used clinically as it is considerably slower
 Arises from RPE – in response to rod signals only
 Represents metabolic activity of Pigment epithelium

16. Physiologic basis of ERG
a wave
Summation of potential change along length of photoreceptors
(Light falling on photoreceptor cells)
Hyperpolarisation of photoreceptor
Cornea negative
a wave is recorded as negative wave
FLASH
STIMULUS
Outer portion
positive
Inner portion
negative

17. Blue dim flash striking dark adapted eye - Rod ERG
Bright red light striking light adapted eye - Cone ERG

18. Rhodopsin consists of Opsin and 11 cis retinal
activates Transducin (bound to GTP)
Activates PDE
Reduced cGMP
light
11cis retinal all trans retinal
Photo activated rhodopsin(Metarhodopsin II)
PDE
cGMP GMP

19. Reduced cGMP
Closure of Na + channels
Decreased release of neurotransmitter
RECEPTOR POTENTIAL
Which marks the beginning of the nerve impulse
Hyperpolarisation
(local graded potential)

22. STEP 1
OPSIN ACTIVATION
STEP 2
OPSIN ACTIVATES TRANSDUCIN
WHICH ACTIVATES PDE
STEP 3
CYCLIC GMP DECLINES ;
GATED Na+ Channels CLOSE
STEP 4
RATE OF NEUROTRANSMITTER DECLINES

23. b wave-
Large positive wave.
Arises from Muller cells in bipolar cell layer, representing the activity of bipolar cells.
Muller cells – modified astrocytes with no synaptic junction
Light strike a photoreceptor
trigger the On- and Off- Bipolar cells
extracellular K+ changes
(K+ is released in amounts related to incident light intensity)
Trigger Müller cell membrane potential changes linear with extracellular K+
Bipolar cell depolarization

25. Thus b wave Is dependant on electrical activity originating within Photoreceptor layer
- Muller Cells provide b wave from rods and cones
Oscillatory Potential
 Seen on photopic light adapted b wave
 produced by Amacrine cells in inner plexiform layer.
 Reflect feedback circuits in inner retina
 Disappear in cone dysfunction syndromes
 Selectively abolished in animals by clamping retinal circulation and in humans aft
er CRAO and in severe diabetic retinopathy
Because the ratio of Rods vs Cones is about 13:1, scotopic B-wave is a measure of the respons
e from the Rod system, especially for dim flash

26. C wave
Generated from RPE cells in response to rod signals only
as rod cells are in direct contact with apical end of RPE cells while
cones do not appear to make such contact

27. ERG arises from parts of retina distal to the ganglion cells
Thus a normal ERG may be recorded from an eye with advanced optic atrophy
Provided that the outer layers of retina are intact

28.  a wave Amplitude is measured from baseline to the trough of a wave
 b wave amplitude is measured from trough of the a wave to the peak of the b wave
 The implicit time is the time from onset of stimulus onset to the peak of a or b response.
considering only a and b wave duration of ERG response is less than ¼ second
 Latency is the time interval between onset of stimulus and beginning of a wave response
.(Normally 2msec)

29. PHOTOPIC NEGATIVE RESPONSE (PhNR)
In flash erg Phnr is the negative
wave following the “b” wave
Amplitude of phnr is measured
from the baseline to the trough o
f the negative wave
This wave is believed to originate
from the ganglion cell layer of th
e retina and is earliest affected in
glaucoma and appears before
visual field defects

30. Recording protocol
 Dark room with non-reflecting walls
 FFA, Fundus photography should be avoided
 Dilate the pupil with mydriatic to maximize the light entering the eye and
minimize the interference from pupil contraction
 Dark adapt > 20 minutes to maximize the rod responsiveness
 Connect the electrodes:
 Corneal electrodes on eyes
 Reference electrode on forehead
 Ground on ear
 Rod response with scotopic blue/dim white light
 Max. combined response with scotopic white light
 Oscillatory potentials
 10 min of light adaptation
 Single flash cone response with photopic white flash
 30 Hz flicker

31. BURIAN-ALLLEN CORNEAL
CONTACT LENS ELECTRODES :
 Multiple use electrode, not commonly used nowadays.
 Placed over the cornea after topical anesthesia.
 Advantages :
 Come in different sizes so can be used for most of the
eyes.
 They can be used for years.
 Disadvantages :
 Expensive.
 Can be uncomfortable for some due to the large size of
the speculum attached.
ELECTRODES USED IN ERG

32.  JET DISPOSABLE ELECTRODE :
 Small monopolar, hard contact lens
electrode which is placed over cornea.
 Requires skin electrode as reference
electrode which is placed on forehead.
 Single use electrodes & quite expensive.

33.  HK LOOPS :
 Plastic coated, pliable wire electrode.
 Placed in lower fornix.
 Can be used in unco-operative patients such
as young children & patients with ocular
 trauma.

34.  DTL ELECTRODE :
 Fine silver nylon fiber electrode with
white adhesive disc at either end.
 Silver fiber is placed in palpebral sac
& discs are attached to
canthi to secure the electrode.
 Single use electrode & quite
expensive,

35.  MAYER’S GOLD PLATED ELECTRODE
:
 Gold foil electrode.
 For Single use.
 Placed in lower fornix with gold comi
ng in direct contact with eye.

36.  SKIN ELECTRODES :
 Silver chloride cup electrodes used as gro
und or reference electrodes.
 Used especially in patients with ocular tr
auma where other electrodes coming dir
ectly in contact with eye cannot be used.
 Sensitive to facial movements so of limite
d value in crying children.

41. Recording protocol
Full pupillary dilatation
30 minutes of dark adaptation
Rod response
Maximum combined response
Oscillatory potentials
10 minutes of light adaptation
single flash cone response
30 Hz flicker

42. Recording
Electrode
Amp.
Reference Electrode
Computer
Ear
Ground
Electrode
ERG Recording Setup
Ganzfeld Dome
ERG Response

44. ISCEV Standard for full-field clinical electroretinography

45. ISCEV ERG Protocol: Step #1 “Rod Response”
 Patient is dark adapted
 there is no background light when ERG is recorded
 The response is “Scotopic”
 A dim flash stimulus (-24 dB), 0.01cd s m-2 with minimum interval of 2s
between flashes
 activates Rod photoreceptor cells but not Cones
 Only B-wave response is recorded
 Useful for the evaluation of Rod function
Scotopic - 24 dB Flash
Scotopic - 24 dB Flash
-200
-100
0
100
200
300
-200
-100
0
100
200
300
0 50 100 150 200
Electroretinogram
1:(µV)Od2:(µV)Os
milliseconds

46. ISCEV ERG Protocol: Step #2 “Maximal Response”
 Patient remains dark adapted, so the response is also Scotopic
 Standard flash stimulus (0 dB), 3 cd s m-2 with minimum interval
of 10 s between flashes
 activates both Rods and Cones
 The response contains both A-wave and B-waves
 In normal retina, this stimulus intensity elicits the maximal respons
e
Scotopic 0 dB Flash
Scotopic 0 dB Flash
-500
-250
0
250
500
-500
-250
0
250
500
0 50 100 150 200
Electroretinogram
1:(µV)Od2:(µV)Os
milliseconds

47. ICSEV ERG Protocol: Step #3 “Oscillatory Potentials”
 Same stimulus as Step #2 also elicits Oscillatory Potentials (OPs),using high
and low pass filters
 OP s ride on the ascending B-wave
 frequency range of 100-160 Hz
 Affected by retinal ischemia: Diabetics, CRVO have reduced OP Amplitude
 OP Amplitude predicts high-risk diabetic patients
-500
-250
0
250
500
-100
-50
0
50
100
0 25 50 75 100 125 150
Electroretinogram
1:(µV)Od2:(µV)Od
milliseconds
Filtered ERG
Unfiltered ERG

48. ICSEV ERG Protocol: Step #4 “Cone Response”
 The patient is exposed to background light (30 cd/m2) for at least 10minutes a
nd then stimulated with a standard flash (0 dB) of 3 cd s m-2 with minimum
interval of 0.5s between flashes
 “Photopic” response
 Rod photoreceptors are bleached by the background light, so response from R
ods is suppressed
 The response is mainly from Cone photoreceptors
1
2
1
2
Photopic 0 dB Flash
Photopic 0 dB Flash
-100
0
100
200
300
-200
-100
0
100
200
0 50 100 150 200
Electroretinogram
1:(µV)Od2:(µV)Os
milliseconds

49. ICSEV ERG Protocol: Step #5 “Flicker Response”
 Flicker stimulation (15-60 Hz) at the standard intensity white stimulus (0 dB)
of 3 cd s m-2 with flash rate of 30 stimuli per second
 elicits photopic response
 The B-wave from Cones is recorded, primarily inner retinal response
 Applications: Retinal Ischemia; cone and rod-cone disorders
1
2
Photopic 0 dB 30 Hz
Photopic 0 dB 30 Hz
Ampl.: 132.7 µV, Latency: 32.8 ms
Ampl.: 135.2 µV, Latency: 32 ms
-100
-50
0
50
100
-100
-50
0
50
100
0 50 100 150 200 250
Electroretinogram
1:(µV)Od2:(µV)Os
milliseconds

50. 1
Dark-adapted 0.01
ERG
A rod-driven response of bipolar cells
2
Dark-adapted 3 ER
G
Combined responses arising from photor
eceptors and bipolar cells of both the rod an
d cone systems; rod dominated
3
Dark-adapted 3 osc
illatory potentials
Responses primarily from amacrine cells
4
Dark- adapted 10 E
RG
Combined response with enhanced a-waves ref
lecting photoreceptor function
5
Light-adapted 3 ER
G
A cone-driven response of bipolar cells
6
Light- adapted 30
Hz flicker ERG
A sensitive cone-pathway-driven response
McCulloch, Daphne L., et al. "ISCEV Standard for full-field clinical electroretinography (2015 update)." Docum

51. Diagnose:
Retinitis Pigmentosa and other inherited retinal degenerations
Congenital and acquired night blindness
Inflammatory conditions
Vitamin A deficiency
Manage:
Diabetic Retinopathy
Central and Branch Vein or Artery Occlusion
Monitor retinal toxicity of drugs such as Plaquenil, Quinine, Cisplatin, Vigabatrin
To assess retinal function when fundus examination is not possible
Corneal opacities
Dense cataract
Vitreous haemorrhage
Prognosis:
Ocular trauma
Detached Retina
Clinical Applications
–

52. A non recordable flash ERG is an ominous sign for visual prognosis.
Disorders result in a completely extinguished ERG
Leber’s congenital amaurosis
Severe retinitis pigmentosa
Retinal aplasia
Total detachment of retina
Ophthalmic artery occlusion
Advanced stage of rod– cone dystrophy
Gyrate atrophy
Choroideremia
Autoimmune retinopathy

53. Factors influencing ERG
Physiological :
 Pupil
 Age - small ERG within hr of birth
declines in adults
 Sex-Larger in females than males
 Ref. Error
 Diurnal Variation
 Dark adaptation
 anesthesia
Limitation of Full Field ERG -
Unless 20% or more of the retina is affected with a diseased state
the ERGs are usually normal
Artifacts :
 Blinking
 Tearing
 eye movements
 air bubbles under electrode.
Instrumental :
 Amplification
 Gain
 Stimulus
 electrodes

54. EYE MODEL BASED IN EOG (BIDIM-EOG)
Bi Dimensional Bi Polar Model

55. PATTERN ERG
• Measure of macular function and generalized bipolar cell function.
• most common stimulus : Checkerboard stimulus composed of white and
black squares
• PERG generation requires physiological integrity of anatomically present
RGCs
• Reduction of PERG amplitude reflect the reduced activity of dysfunctiona
l RGCs
• reflects inner retina activity under light-adaptation.
• should be used in combination with a traditional light-adapted luminance
ERG to have an index of outer retina function
• an important tool to monitor the onset and the progression of RGC
dysfunction in optic nerve disease.
Example:-
Glaucoma, optic neuritis, ischemic optic neuropathy, and mitochondrial
optic neuropathy

56. Principle :
Net retinal illumination remains constant.
Only a redistribution of the pattern of light
and dark areas is made
 17” monitor from a distance of 1
meter
 stimulus field is 15 °
 150 stimuli for signal averaging at a
frequency of 1 pulse per second
 Central fixation is necessary.
 Refraction to be corrected
 Use temporal fossa for reference electrod
e, and forehead for ground electrode.
 Recording electrode: DTL or Gold Foil Elec
trode (no lens electrode)

57. The normal pattern electroretinogram :
– N35- a small negative component with a peak time
occurring around 35 ms;
– P50- a prominent positive wave emerging around 50 ms
– N95- a wide negative wave around 95 ms

58. Can help differentiate Macular from Optic nerve related pathologies
in Macular diseases:-
The P50 component was shown to be altered in all patients with retinal and macular diseases
in Optic nerve disease:-
N95 component was abnormal in 81% of patients with diseases of the optic nerve.
The P50 component remain normal.

59.  MFERG tests ERG activity in individual small retinal areas in
central 30° area
 Erich Sutter used binary m-sequences to extract hundreds of focal
ERGs from a single electrical signal.
 Stimulation is provided by video display
 Sophisticated algorithms extract the response of each retinal area
from the overall recording
 Photopic test (cone function)
 Response amplitude related to cone density.
 Typically, stimulus areas are scaled to provide equal response.
Multifocal ERG (MFERG): Mapping of Retinal Function

60. MFERG: The Concept
Recordin
g Electro
de
Amp.
Referenc
e Electro
de
Computer
Ear
Ground E
lectrode
Stimulus on high-qua
lity video monitor

61. MFERG: The Individual Response
and 3-Dimensional Display
Blind spot Foveal peak
3D display of ERG response densityFocal ERG from each retina area

62. MFERG: Map And Focal
• Analyze summarized ERG responses from different regions
• Analyze the overall response from the central retina area of 50 - 600
view angle

66. • Small scotomas can be mapped and
quantified
• 61 or 103 focal ERG responses can be
recorded from the cone-driven retina.
• 20-30 degrees to each side of the
fovea

67.  Dilate patient’s pupil with a mydratic
 No dark adaptation is necessary.
 Refractive correction is recommended but not required.
 Recording using Burian-Allen or DTL electrode on the eye,
a reference electrode (only for DTL)
a ground electrode
 The test is composed of several segments, 10 - 30 seconds each
 Total recording time is 5 - 10 minutes per eye
 It is critical that patient is staring at the fixation during recording; the eye
can be monitored using a fixation camera
 Eye or body movement will distort the recording, and the segments shou
ld be repeated if there is too much noise
MFERG: Recording Procedure

68.  Diagnosing macular disease:
ARMD, others
 Retinal toxicity (Plaquenil and other drugs)
 AZOOR (Acute Zonal Occult Outer Retinopathy)
 Macula vs optic nerve in unexplained visual loss
 Early diagnosis of retinal disease: Many retinal disorders affect small
areas in early stages
Diabetic retinopathy
Retinitis pigmentosa
MFERG: Applications

70. Additional Tests
Very bright flash (+25dB)
for pre-operative evaluation
In Dense cataract and Vitreous hemorrhage
Photopic Negative Response ERG
Test condition: Dilated, photopic test
Stimulus: Red Flash on Blue Background
Generated by retinal ganglion cells
Early glaucoma evaluation
On/Off Response ERG
Test condition: Dilated, photopic test
Stimulus: Red Flash on Blue Background
Looking at On and Off Bipolar Cells responses
Inner retina dysfunction

71. S-Cone ERG
Test condition: Dilated, photopic test
Stimulus: Blue Flash on Amber background
Generated by S-Cone Photoreceptors
Enhanced S-Cone Syndrome
Scotopic Threshold response ERG
Test condition: Dilated, scotopic test
Stimulus: Series of flash of increasing intensity starting from below thres
hold (starting intensity is species dependent)
Double Flash ERG
Stimulus: Bright Flash followed by medium flash

72. Electrooculogram
Measurement of resting potential of eye
Which exist between cornea and back of the retina
During
fully light adapted and
Fully dark adapted conditions
Records overall mass response only.
 Records the “Corneo-Fundal Potential”
 Measures function of Retinal Pigment Epithelium (RPE)

73. Mainly derived from the response of retinal pigment epithelium (RPE)
to retinal illumination
Amplitude of potential changes with retinal illumination over a period of mi
nutes
• Dark: smaller potential
• Light: larger potential
• The potential decreases for 8–10 min in darkness.
• Subsequent retinal illumination causes an initial fall in the standing po
tential, followed by a slow rise for 7–14 min (the light response).
• These phenomena arise from ion permeability changes across the
basal RPE membrane.

74. EOG recording
 Arrangement to make the eyes light adapted with a bright long duration
stimulus
 Dilate (>3 mm) with mydriatic
 Skin electrodes near both canthi of BE
 Ground electrode at forehead.
 3 dim , red fixation lights 15o apart
 Looks left & right with 30o excursion at rate of 15—20 rotations per minute.
 Base line. Keep lights on for 5 min
 Turn off the lights. Record for 15 min in dark adapted state
 Turn on the lights. Record for 15 min in light adapted state
 Recordings sampled at 1 min intervals
 Response decreases progressively during dark adaptation
1-
1+ 2- 2+

77. • Calibration of the signal
• Gazing at consecutively at two different fixation points located at
known angle apart and recording the concomitant EOGs .
• Skin electrodes on both sides of an eye the potential can measure th
e potential by having the subject move his or her eyes horizontally a s
et distance .

78. After training the patient in the eye movements, the lights are turned off.
About every minute a sample of eye movement is taken as the patient is asked to
look back and forth between the two lights .
After 15 minutes the lights are turned on and the patient is again asked about
a minute to move his or her eyes back and forth for about 10 seconds.
Typically the voltage becomes a little smaller in the dark reaching its lowest
potential after about 8-12 minutes, the so-called “dark trough”.
When the lights are turned on the potential rises, the light rise, reaching its peak in
about 10 minutes.
When the size of the "light peak" is compared to the "dark trough" the relative size
should be about 2:1 or greater .
A light/dark ratio of less than about 1.7 is considered abnormal.

81. Arden’s ratio
>180% Normal
165—180% Borderline
<165% Subnormal
Difference of >10% in BE is significant
Good pt cooperation is required
Arden Ratio = maximum height of light peak (LP) x 100
minimum height of dark trough (DT)

82. 2 components of EOG
A)Light sensitive – [ Light peak ]
- Contributed by rods and cones
B) Light insensitive – [ Dark trough ]
- Contributed by RPE , Photoreceptors ,inner nuclear layer
Three phases are typically recorded in EOG
The pre-adapt light phase is to standardize the standing potential, taking 1-5 min.
The dark-adapt phase is to “discharge” the standing potential, taking 10 - 20 min.
The light phase is to “recharge” the standing potential, taking 4 - 10 min.
The test takes about 30 - 40 min in total. Recording of both eyes are recommended to
save time

83. Indications
1. Best’s Disease (Best’s Vitelliform Macular Dystrophy)  markedly redu
ced with Arden ratio is less than 120%
2. Butterfly pattern dystrophy
3. Chloroquine toxicity
4. Stargardt’s dystrophy
5. Retinal pigmentary degenerations
6. Chorioretinal dystrophies (e.g. choroideremia)

84. ‘visually evoked response (VER)’ or ‘cortical potentials’.
 It is the electrical response of the brain to sudden app
earance / disappearance / change of visual stimulus.
 Like EEG, VEP is detected by placing surface electrode
s at scalp which can be placed anywhere, but should
always include posterior occipital area.
VISUALLY EVOKED POTENTIALS (VEP)

85. 1. Pattern VEP (checker-board patterns
on TV monitor)
2. Flash VEP (diffuse flash light for
uncooperative subjects)
TYPES OF VEP

86. • Gross electrical signal generated at visual cortex in res
ponse to visual stimuli
• Impulses carried to visual cortex via visual pathway recorded
by EEG
• It is the only objective technique to assess clinical and functio
nal state of visual system beyond retinal ganglion cells
• Measures function of visual pathway: fovea, optic nerve, prim
ary visual cortex

87.  Pupils are un-dilated .
 Patient seated about 1 meter from monitor
 Electrodes in midline at forehead, vertex & occipital lobes
Procedure

88.  The occipital electrode (Inion) lies near visual area thus called as reference
electrode.
 The vertex electrode is placed over non visual area which detects minimu
m activity in response to visual stimulation is called as active electrode.
 The 3rd electrode is placed over forehead is called ground electrode.
VEP ELECTRODES

89.  The stimulus shown
flash of light (diffuse light spot, annulus )
patterned stimulus (illuminated checkerboard)
 The stimuli are repetitively presented at random within a short period of ti
me. Eg. 1 cycle/second for 100 seconds.
 Normally use pattern stimulus (less variability)
Alternating grating, sinusoid, or checkerboard pattern
Stimulus may be full field or hemi-field
 Signals at visual cortex are recorded

91. Normal waveform
Pattern VEP has initial –ve (N1) +ve(P1)second –ve (N2) wave
Positive wave – 70 100 ms
Negative wave – 100 – 130 ms
Positive wave - 150 –200 ms
Flash VEP is complex. 2 positive & 2 negatives.

92.  Amplitude of VEP : Height of the potential of P100 wave. Predominantly
affected in ischemic disorders.
 Latency of VEP : Time from stimulus onset to peak of the response. Pred
ominantly affected in demyelinating disorders.

93. APPLICATIONS OF VEP
 Recording visual acuity in nonverbal patients.
 Macular function test.
 Screening and early diagnosis of Multiple Sclerosis.
 To identify optic nerve diseases, visual pathway abnormalities.
 Amblyopia : latency relatively spared, so VEP can be used to monitor
response to occlusion therapy.
 Detection of a malingerer.
 To detect color blindness : Using chromatic patterned light stimuli

94. DIABETIC RETINOPATHY :
 In DR there is reduction in amplitude &
delay of peak implicit times.
 These changes are directly proportional to
severity of retinopathy.
 Amplitude of oscillatory potentials (OP)
is a good predictor of progression of
retinopathy from NPDR to PDR.
 Abnormal amplitude of OP indicate high
risk of developing PDR.

95. RETINAL DETACHMENT (RD) & CENTR
AL SEROUS RETINOPATHY (CSR) :
 In RD & CSR there is significant
reduction in ERG amplitude.
 However there is no significant
change seen in waveforms of ERG.

96. RETINOSCHISIS :
 ERG in retinoschisis is typically
characterized by marked decrease
amplitude or absence of b wave.

97. RETINITIS PIGMENTOSA :
Retinitis Pigmentosa
 A full field ERG in RP shows marked reduction in both rod &
cone signals although loss of rod signals is predominant
 There is significant reduction in amplitude of both a & b
waves of ERG.

98. CRAO :
 In vascular occlusions like CRAO, ERG t
ypically shows shows absent b wave.
 Ophthalmic artery occlusions usually re
sults in unrecordable ERG

99. CONE DYSTROPHY :
 ERG in cone dystrophy shows good
rod b-waves that are just slower.
 The early cone response of the scotop
ic red flash ERG is missing.
 The scotopic bright white ERG is fairly
normal in appearance but with slow
implicit times.
 The 30 Hz flicker & photopic white ER
Gs which are dependent upon cones
are very poor.

100. RETAINED IOFB :
 A retained metallic FB like iron & cop
per shows changes in ERG early as we
ll as late stages.
 A characteristic change is b-wave am
plitude is reduced by 50% or more a
s compared with normal eye.
 No intervention finally results into an
unrecordable ERG (Zero ERG)

101. A small piece of stainless steel or plastic outside the macula may have a minor aff
ect on the retina.
A piece of copper or iron have deleterious affects within a few weeks
In general if b-wave amplitudes are reduced 50% or greater compared to the
fellow eye, it is unlikely that the retinal physiology will recover unless the fore
ign body is removed.

102. BEST’S DISEASE
Vitelliform lesions represent the accumulation of
lipofuscin in the macular area. Further effects of
retinal pigment epithelium (RPE) dysfunction incl
ude accumulation of degenerated photoreceptor
outer segments in the subretinal space.
Normal ERG, Abnormal EOG :
Clinical utility : Carriers ; end stage disease

103. MULTIPLE SCLEROSIS :
 Abnormalities in VEP are bilateral & seen 90 % of cases irrespective of
visual symptoms.
 In MS, increase in latency period is more predominant than decrease in
P100 amplitude.

104. TOXIC & COMPRESSIVE OPTIC NEUROPATHY :
 Following 2 changes are seen :
 Decreased amplitude of P100 wave.
 Increase in latency period.
 Decreased amplitude of P100 is more predominant than increased
latency period.

105. OPTIC NEURITIS :
 In optic neuritis, VEP shows increased
latency period &/or decreased amplit
ude as compared to normal eye.
 These findings develop even before o
ccurrence of visual symptoms & color
defects.
 In recovery stage, amplitude may retur
n to normal but latency period continu
es to be decreased.

106. Stationary rod dystrophies
Congenital stationary night blindness (CSNB) is
found in several forms.
Two types.
Type 1 have an abnormal dim scotopic ERGs b
ut the bright flash ERG maintains oscillatory po
tentials on the ascending limb of the b-wave.
Type 2 has a very abnormal dim scotopic ERG
and the bright flash scotopic ERG has a large a
-wave and no b-wave.
Oscillatory potentials are also missing

107. Drug toxicities
Several drugs taken in high doses or for l
ong periods of time can cause retinal deg
eneration with pigmentary changes.
The effects of toxic medications can be
detected and quantified using ERGs.
The effects of toxic medications can be
detected and quantified using ERGs.
Chloroquine retinopathy appears as a
characteristic “bullseye” maculopathy

108. The better substitute for chloroquine, Pla
quenil, can also have macular effects noti
ceable by multifocal electroretinograms.
Hydroxychloroquine (Plaquenil) is usually l
ess disruptive to the retina than chloroqui
ne, but ERG changes can still occur.
Vigabatrin, a pediatric seizure medication,
can be toxic to the retina.
Attenuation of full-field ERG b-wave amp
litudes can detect toxicity.
Often the first indication of toxicity is red
uced amplitude to 30 Hz flicker
Cis-platinum used to treat brain tumors s
ometimes reaches ophthalmic vascularizat
ion and causes a reduction in ERG wavef
orm in the affected eye (OD in this case)

109. Steroid Retinopathy
The fundus photo shows a cherry red spot in th
e macula.
The ERG response was diminished in size
particularly following dim scotopic flashes

110. Talc retinopathy
Seen in iv drug abusers
Global ERG is attenuated

111. OGUCHI DISEASE
Absent rod ERG
Normal cone ERG
Negative configuration of combined response; normal OP
Photopic hill phenomenon
Improvement after prolonged dark adaptation

112. FUNDUS ALBIPUNCTATUS
Rod ERG absent after 30 min dark ad
aptation
Normal after 3 hour dark adaptation
Combined response : negative after 3
0 min, normal after
3 hours

113. REFERENCES
1.The electroretinogram and the electro oculogram : Clinical applications
By Donnell J. Creel
2.Neuro- Ophthalmology Clinical signs and symptoms
By Thomas J Walsh
3.Electrodiagnosis of Retinal Diseases
By Y. Miyake
4.Diagnostic Procedures in Ophthalmology
BY HV Nema
5.Anatomy and Physiology of the eye by A.K. khurana
6.Clinical Neurophthalmology by Ulrich Schiefer
7.Clinical Anatomy and Physiology of the visual system by Lee Ann
Remington

114. THANK YOU
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