60 Published by : INAVRShttps://www.inavrs.org/| International Journal of Retina https://ijretina.com 2020; 03; 02; 

International Journal of Retina (IJRETINA) 2020, Volume 03, Number 02. 
P-ISSN. 2614-8684, E-ISSN.2614-8536 

 

 

 

COMPARISON OF WAVE AMPLITUDE, IMPLICIT TIME AND COMFORT 

LEVEL USING DAWSON-TRICK-LITZKOW, JET AND DENCOTT 

ELECTRODES IN ELECTRORETINOGRAPHY IN NORMAL ADULTS 

Theresia Yinski PG1, M. Sidik1, Syntia Nusanti1, Aria Kekalih2 
1Ophthalmology Department Medicine Faculty Universitas Indonesia  

2Community Medicine Department Medicine Faculty Universitas Indonesia 

ABSTRACT 

Introduction: Several electrodes can be used in standard full-field electroretinography (ERG). However, there 

are no standard values for Indonesians yet. Therefore, this research aims to establish normal values, to 

compare them and to compare comfort levels using DTL, Dencott and Jet electrodes in Indonesian adults. 

Methods: This was a correlative analytical study as well as a population descriptive study which took place in 

Ciptomangunkusumo Hospital over the course of April-August 2016. Through convenient sampling, 58 

normal Indonesian subjects, age 19-49 years old were selected. ERG amplitudes and implicit time values were 

measured according to recommendations by the International Society for Clinical Electrophysiology of Vision 

(ISCEV). Evaluations consisted of scotopic 0.01, 3.0, OP and photopic 3.0 flicker. After examination, all 

subjects filled in a questionnaire about comfort levels, adopted from the visual analog scale of a 10 

centimetre line. The score was later measured by ruler in centimetres.    

 

Result: Pearson/Spearman correlation shows moderate to strong correlation between all parameters in the 

3 electrodes (r≥0.3). The paired t-test analysis showed a statistically significant difference in ERG normal 

values between electrodes with higher wave amplitudes and longer implicit times in Dencott and jet 

electrodes, compared to DTL electrodes (p<0.05). Jet and DTL electrodes are more comfortable than Dencott 

electrodes for Indonesian adults in standard full-field electroretinography with scores of 5.21 (Dencott), 6.93 

(Jet) and 7.64 (DTL). 

 

Conclusion: DTL electrodes give the lowest wave amplitudes and the shortest implicit times and are the most 

comfortable electrode compared to Dencott and ERG jet electrodes, in standard full-field electroretinography 

in Indonesian adults. 

Keywords: electroretinography, Dencott, DTL, Jet, electrode 

Cite This Article: GONDOSARI, Theresia Yinski Pistari. Comparison of Wave Amplitude, Implicit Time and 

Comfort Level Using Dawson-Trick-Litzkow, Jet and Dencott Electrodes in Electroretinography in Normal 

Adults. International Journal of Retina, [S.l.], v. 3, n. 2, sep. 2020. ISSN 2614-8536. Available at: 

<https://www.ijretina.com/index.php/ijretina/article/view/123 

 

 

INTRODUCTION 
 

 

*Correspondence to: 

Theresia Yinski PG,  

Department of Ophthalmology 

Universitas Indonesia, 

cyinski@hotmail.com 

 

 

Electroretinography is a very important type of examination since it can be used to evaluate 

the retina function objectively and can calculate the results in numbers. Electroretinography 

may serve as baseline data and follow up measurement for therapy, as well as a means to 

predict the prognosis of patients if surgery is considered.1,2 The International Society for 

Clinical Electrophysiology of Vision (ISCEV) recommends that every centre should have its own 

normal set of data because the characteristics of patient vary widely.3,4 Nowadays, there is 

quite a wide variety of electrode types 



 

 

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which can be used for the electroretinography 

examination, such as scleral electrodes, corneal 

electrodes and eyelid electrodes. Good electrodes are 

important in order to produce a good 

electroretinography wave result. However, we should 

not forget to also consider the patient’s comfortability in 

wearing the electrodes during the examination. Despite 

a lot of types of electrodes, the standard depends on the 

parameter used in the electroretinography examination 

and therefore there is no methods difference per 

electrodes usage. There are three main groups of 

electrodes which are scleral, corneal and eyelid 

electrodes.  

In this research we limited the comparison to Dencott 

electrodes as the example of scleral electrodes, Jet 

electrodes as the example of corneal electrodes and 

Dawson-Trick- Litzkow (DTL) electrodes as the example 

of eyelid electrodes. This research aims not only to 

establish the normal values of standard full-field 

electroretinography at our hospital for the Indonesian 

population, but also to compare the values and comfort 

levels of using the 3 types of electrode in Indonesian 

adults. 

 

METHODS  

This study is a correlative analytical study which 

compares the normal results of standard full-field 

electroretinography as well as the comfort level of the 

electrodes usage in normal Indonesian adults. However, 

this study also serves as population descriptive study as 

it gives normal standard values for electroretinography 

examination in Indonesia. All 58 subjects, ages between 

19-49 years old, were selected through convenient 

sampling and their normal status of both eyes were 

established through a series of examinations of visual 

acuity, intraocular pressure, Humphrey visual field, 

anterior segment evaluation, fundus photography, 

Ishihara colour blind test and Pelli-Robson contrast 

sensitivity test, over the course of April-August 2016. 

Subjects were excluded if they had high myopia (≥ 6 

dioptres), a history of intraocular surgery or laser 

treatment (photocoagulation), eye trauma, long-term 

drug usage or difficulty in pupil dilation. 

The electroretinography examination was performed 

based on ISCEV recommendations. The order of 

electrode usage was randomised per subject, but all of 

the examinations was done on the same day for each 

subject by the same operator. ISCEV recommendations 

are as following:  

1. Pupil dilation is done with tropicamide 1% prior 

to the examination 

2. A drop of tetracaine 0.5% is used as topical 

anesthetics in both eyes 

3. 20 minutes of dark adaptation is done prior to 

the placement of the electrodes (based on the 

randomisation order) and subjects are instructed to 

look straight forward to the fixation point in the 

machine dome for the scotopic 0.01 and 3.0 ERG and 

3.0 OP 

4. Afterwards, 10 minutes of light adaptation is 

done prior to the photopic fast flicker 30 Hz ERG 

The questionnaire about comfort levels, adopting the 

visual analog scale of a 10 centimetre line, was given to 

the subjects after they had completed all examinations. 

The score was later measured by ruler in centimetres.  

All procedures performed in this study involve human 

participants and therefore the procedures were in 

accordance with the ethical standards of the institutional 

research committee and with the 1964 Helsinki 

declaration and its later amendments or comparable 

ethical standards. This research has been approved by 

The Ethical Committee of the Medicine Faculty of 

Universitas Indonesia based on the Helsinki Declaration 

and ethic permission has been obtained. Informed 

consent was obtained from all individual participants 

included in the study. 

 

RESULTS 

The image below can further clarify the results of the 

standard full-field electroretinography examination. 

 

 

 

 

 

 

 

 

 

 

 

From the 58 subjects recruited, 43 were female, totaling 

116 eyes. Pearson/Spearman correlation showed 

moderate to strong correlation between the three 

electrodes in all of the parameters measured, as given in 

table 1.



 

 

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Table 1. Correlation between Electrodes 

Parameter Correlation (r) 

Dencott vs Jet Dencott vs DTL Jet vs DTL 

Implicit time of b wave Scotopic 0.01  0.626 0.609 0.650 
Amplitude of b wave Scotopic 0.01  0.604 0.436 0.572 
Implicit time of a wave Scotopic 3.0  0.737 0.476 0.487 
Amplitude of a wave Scotopic 3.0  0.564 0.358 0.388 
Implicit time of b wave Scotopic 3.0  0.615 0.582 0.641 
Amplitude of b wave Scotopic 3.0  0.826 0.668 0.649 
Implicit time of OP wave  0.382 0.300 0.392 
Sum amplitude of OP wave  0.787 0.584 0.688 
Implicit time of b wave Photopic Flicker  0.623 0.565 0.636 
Amplitude of b wave Photopic Flicker  0.640 0.467 0.584 

 

Normal values of standard full-field electroretinography in Indonesian adults, using Dencott electrodes, Jet 

electrodes and DTL electrodes, are shown in table 2. The p-values were obtained from the paired t-test analysis. 

 

Table 2. Normal Values of Standard Full-field Electroretinography in Indonesian Adults 

Parameter Dencott Jet DTL 

Imp.time b wave Scotopic 0.01 77+7 76+6 74+7*^ 
Amp. b wave Scotopic 0.01 293 (133-544) 332 (109-576)* 283 (146-496)^ 

Imp.time a wave Scotopic 3.0 25+1 25+1 24±1*^ 
Amp. a wave Scotopic 3.0 -258 (-445;-138) -281 (-459;-132)* -220 (-358;-100)*^ 

Imp.time b wave Scotopic 3.0 45+3 46+4 46+5 
Amp. b wave Scotopic 3.0 482 (315-737) 509 (261-771)* 417 (202-724)*^ 

Imp.time OP wave 21+1 21+1 21+1 
Sum amp. OP wave 345 (106-589) 338 (149-797) 281 (107-717)*^ 

Imp.time b wave PhotoFlicker 29+2 29+2 29+2 
Amp. b wave PhotoFlicker 105 (44-236) 108 (44-264) 88 (37-186) * 

*) p value < 0.05 compared with Dencott 
^) p value < 0.05 compared with Jet 

 

The mean comfort level scores from the questionnaire using each electrode are shown in table 3.  

 

Table 3. Mean Comfort Level Score of Electrode 

Electrodes Mean Comfort Level 
Score Dencott 5.21+2.5 

ERG Jet 6.93+2.3 

DTL 7.64+1.8 

 

The paired t-test comparison between the electrodes are shown in table 4. 

 

Table 4. Comparison of Comfort Level between Electrodes 

Electrode Comparison p value 

Dencott – ERG Jet 0.001 

Dencott – DTL  0.001 

ERG Jet – DTL  0.064 

 
There were no side effects or complications, such as eye infection or corneal abrasion, in any of the subjects during this 

research. 



 

 

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DISCUSSION 

Standard full-field electroretinography is an important 

clinical tool that provides an objective quantitative 

measure of retinal function. Decreased a and b wave 

amplitudes and prolonged implicit time correlate to 

reductions in retinal function.1 Because of the wide 

variety of patient characteristics, ISCEV recommends 

that every laboratory should have its own normal data 

using ISCEV protocols so that it becomes comparable all 

over the world.1,3,4 However, until this time, there has 

been no research done in Indonesia regarding this 

matter.  

Correlation analysis shows moderate to strong 

correlation between all parameters in the 3 electrodes. 

This explains that the higher the values are collected with 

Dencott electrodes, the higher the values will be 

collected with the two other electrodes. This result is 

similar to the research conducted in Japan by Kuze, et al. 

5 

The electrode order was randomised to eliminate the 

possibility of bias of eye fatigue or electrode type. The 

recording conditions also specify 20 minutes of dark 

adaptation before recording dark-adapted 

electroretinography (scotopic), and 10 minutes of light 

adaptation before recording light-adapted 

electroretinography (photopic) according to ISCEV 

standards.6 

This research shows that ERG jet electrodes give a 

higher amplitude than the other electrodes, with DTL 

giving the lowest. This happens because the DTL is quite 

far located from the centre of the cornea if compared 

with Dencott or Jet electrodes.5 However, the implicit 

times are not significantly different between electrodes, 

even though the material of each electrode is different. 

Silver, the material of DTL electrodes, has the highest 

conductivity of 6.8 x 107 (Ωm)-1, while gold, the material 

of Jet electrodes, has conductivity of 4.3 x 107 (Ωm)-1.7 

In Malaysia and Iran adults the normal values of 

scotopic a and b wave amplitude is lower than in the 

Indonesian population when the recording is done by 

using DTL electrodes.8,9 Similar results are shown in 

research from Korea using Jet electrodes, which show 

lower results of wave amplitudes compared to the 

Indonesian population.10 However, it proved difficult to 

compare this research’s results with other research, 

because the differences of electroretinography 

machines, as well as the electrodes, may contribute to a 

variety in results. 

Race is known to be another factor that contributes to 

the difference of results. One research, comparing the 

Caucasian and Asian populations, showed that 

Caucasians tend to have a higher wave amplitude than 

Asians. The hypothesis of what cause this is said to be 

the ocular pigmentation of iris, in which melanine serves 

as a resistant barrier for the electroretinography wave 

signal.11  

The results from the questionnaires given to the 

subjects reveal that DTL electrodes give the most 

comfort of the three electrodes used. This is because of 

the position of the electrode, which is buried deep in the 

lower fornix, thus barely being in contact with the 

cornea. The electrode’s position is stable as well, as the 

position is not necessarily affected by blinking of the eye. 

However, statistical analysis shows that there is no 

significant difference between DTL and Jet electrodes, 

which are shaped as contact lens touching the cornea.   

The most ideal electrode is the one that give the 

highest amplitude, has low variability, and is well-

tolerated by the patients (most comfortable). The study 

by Mohidin N, et al shows that corneal electrodes such 

as Jet electrode may give a high variability because it 

tends to easily slide during blinking.12 This makes the 

DTL as a non-corneal electrode a more favourable 

choice, as its variability is low due to its stable 

position.13 Dencott electrodes are the least favourable 

electrode due to their discomfort, caused by their bulky 

shape. However, its long legs make it stable, because 

once it is positioned well on the eye surface, it will not 

move even with rapid eye blinking. 

In the future we hope to be able to conduct the 

examination with more varieties of electrodes on 

children as well as the geriatric subjects so that more 

complete normal standard values ERG can be obtained 

for all age population groups and more types of 

electrodes. 

 

CONCLUSION  

There is a statistically significant difference in the wave 

amplitudes between Dencott, Jet and DTL electrodes. 

DTL and ERG jet electrodes are the most comfortable 

electrodes in standard full-field electroretinography for 

normal Indonesian adults. Due to the presence of many 



 

 

64 Published by: INAVRShttps://www.inavrs.org/| International Journal of Retina https://ijretina.com 2020; 03; 02; 

parameters in the examination, the normal values of 

wave amplitude, implicit time and comfort levels of the 

three electrodes are given in the result section. 

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