Dear David,

Solid gel electrodes, particularly the Ambu Neuroline surface line, are  suitable for high frequency OEG recordings. I have not tried any different brand, but I´m sure Ambu is not the only one.

Best,

Mario

Dear David,

Solid gel electrodes, particularly the Ambu Neuroline surface line, are  suitable for high frequency OEG recordings. I have not tried any different brand, but I´m sure Ambu is not the only one.

Best,

Mario

Dear Mario, thanks a lot!

I've had good experience using 10mm gold cup electrodes from Nicolet or Grass.  We use them for EEG and EMG as well.  With a good skin prep, some conductive gel, and a strip of medipore tape, the data looks great.  I have also used 6mm pediatric gold cups for recording EMG from the corrugator muscles with good results.

If you intend to record fast movements, then the nature of the electrodes is of less importance. However, if you want to study slow movements or longer fixation periods, then you should try some different kind of electrodes to test when you get the most reliable signal. In that case, however, EOG is should be not the recording method of choice.

Thanks, Will! Maybe we'll try cup-electrodes as well. My only concern would be to place them in a way, such that the participant is not influenced by the tape (especially for the vertical ones, how do you get close enough to the eye without getting tape on the lower lid...). But I think, we'll give it a try, when the Ambu Neuroline electrodes are not satisfying

Thanks, Evangelos for the comment. Since we are observing real-life behavior, our eye movements will include a broad mixture of slow and fast eye movements and since we are trying to develop a mobile device for physiological signals we are also bound to  EOG.

Greetings, David

No problem, David.  Currently, I mostly do unattended, in-home recordings with patients with Parkinson's and other neuromuscular disorders, so I am biased toward whatever offers the most secure attachment. I usually end up taping electrode pads down if I want them to still be in place the next day.  In regards to the tape placement, you have to do it carefully.  1 inch perforated tape usually has enough width to secure the electrode and not intrude onto the lower lid.  There only has to be a few mm of tape over the top of the electrode head to secure it, as along as the rest of the head is covered by tape. 

In my many field studies I have used Ag/Ag-Cl cup electrodes affixed carefully with collodion.  For example, TECHNOMED Cup Electrodes with Silver/Silver Chloride Plated Disc (TE-C22), viewable at http://kingmedical.com/neurology-diagnostics/eeg-supplies/reusable-eeg-electrodes/technomed-cup-electrodes-with-silver-plated-discs-430.html.  With practice, you can get an electrode placement like this to last more than 24 hours, given not too much sweating.

Make sure that the subject's head is turned such that liquid would roll away from the eye.  Be gentle with skin cleaning before electrode application -- this is a skin area that marks easily.  Also, cleaning so much that the electrode connects with body fluid makes the body an antenna for ambient electrical noise.  Just swab gently with alcohol on a cotton pad to remove surface oil.  For electrode removal, I soften the collodion with non-acetone nail polish remover on cotton, holdng the moist cotton gently against the electrode.  Then pull the electrode off gently.

You don't have to be super-close to the eye.  Recall that the Rechtschaffen and Kales standard indicates about 1 cm from the outer canthus.

The Ag/Ag-Cl electrodes will allow you to pick up  slow eye movements, including the slow, rolling eye movements associated with Stage 1 drowsiness, as well as saccades and pursuit.  Of course, you won't get all the way down to DC or get good absolute angle values, as you would with an eye tracker.

Thanks James, that was also a pretty helpful comment! Since I previously used only optical eye trackers, I haven't thought of the cleaning so much (which resulted in considerably marking myself after testing).

Since also Will suggested cup electrodes, we will definitely try them. Currently, I ordered the Ambuline solid gel electrodes for further testing. I will report  how that went.

Greetings, David

I agree with James about the skin cleaning- be as gentle as possible, and always proceed in a manner to avoid contact with the eyes.  The electrodes should never be placed on broken skin.  In addition to the increased impedance from contact with body fluids, the patient will experience much discomfort from broken skin and infection control protocols become more involved.

  I usually prep the skin with Nuprep using a cotton tipped applicator for a three count, the skin will just start to redden on many people at this point.  It takes a little practice to gauge how much force to use when prepping the skin, the goal is remove oils and loose cells, not the top layer of skin.  I have trainees practice a few times on their forearms using a swap and Nuprep, if their skin just begins to sting at 3 seconds, they are using about the right amount of pressure.  I  wipe away any excess Nuprep using a gauze square before electrode application.  Also, the age and health of the patient is a factor.  For example, skin thins secondary to chemotherapy, making it more fragile.  Additionally, the thinned skin of elderly patients can be broken easily.  In these cases, we forgo using Nuprep and do a few passes with an alcohol pad to improve signal quality.  The trace won't be as low impedance as one with skin prep using an exfoliant, alcohol tends to dehydrate the skin and increase impedance initially, but avoiding broken skin and undue discomfort are more important.  

Avoid the eye by always prepping the skin using vertical motions. 1 cm from the outer canthus gives room for the applicator swab, but an unexpected head movement from the patient can result in abrading the cornea if prepping using horizontal motions.

Dear all,

now i tested the Ambu Neuroline 700 solid gel EMG electrodes and found them to give a pretty good signal. In addition, they are quite pleasant to wear. A slight disadvantage is, that they will reduce (not loose) the contact after a longer wearing period (5 hours) when the subject is sweating, For skin preparation I first applied an abrasive cleaning gel and then removed the remainders with ether, which is not as irritating for the skin as alcohol.

The 700 are the "bigger" ones of this series, I also ordered the 710, which are smaller. Will give an update, when I got them.

Greetings, David

Dear Mack and Mario,

I have tried Ambu electrodes, it work pretty well. Especially in the stress test, the motion artifact is greatly reduced.

Thank you for the advice from all of you.

Huanqian Zhang

Dear David, thanks for posing this question. Which electrodes have you decided to use? What's your experience? We're as well starting with EOG and looking for suitable solutions. Thanks! Cornelia

Historically, 10-mm silver chloride cup electrodes held on and covered with collodion have worked well for ambulatory recording across 12 to 24 hours.

Dear Cornelia,

I have used the Ambu Neuroline 710 Electrodes. These are comfortable to wear and reasonable small. Their re-seller in Switzerland (Synmedic) was very friendly and provided us with several try-outs. The 710 were the best ones in terms of size-signal-quality ratio. 

Only drawback is the jelly, which peals of the electrodes if they are too warm (or worn for a longer time). Don't know how bad that becomes during very long recordings (e.g. over several hours). For our purposes that wasn't much of a deal.

Greetings, David

Hello

I have seen many articles about the steps of designing Electrooculogram (EOG) circuits but these steps vary from article to article so I want to ask what are the recommended steps

It's indeed a tricky answer, and you must have a trade-off between cost and performance. It also entirely depends on your end-application. You can use passive electrodes such as Platinum, Gold, Silver, Copper.

The contact surface area also matters. Copper would just tell you if any movement has occurred, not the dynamics accurately. Gold and Platinum would give you very good sensing, conditioned to the instrumentation is proper.

Active electrodes are also desirable as they give good signal gain. Wet electrodes have good conductivity but poor comfort.