Care and Use of Gold Foil corneal electrodes

 

NB. These electrodes should only be used by suitably qualified persons.

 

Placement of electrode.

The electrode is placed in the lower fornix in line with the inferior corneo-scleral junction and secured with tape, (e.g. 2.5cm Micropore, 3M) fastened to the cheek. Placement should be such that the junction of the foil and wire is clear of the skin. (see figure). An acute bend in the connecting lead should be made created such that the loop points laterally preventing rota¬tion of the electrode.

Insertion of the electrode.

The patient should look upwards, the lower lid is then drawn down and out, the electrode is placed on the lower lid so as not to entangle the eye lashes. The patient is instructed to look straight ahead, the lid is slowly released. The electrode is allowed to contact the corneo-scleral junction in the midline. Although not recommended, topical local anaesthetic may be used to overcome any initial discomfort.

 

Removal of the electrode.

This is the reverse of insertion.

 

Cleaning, care and storage.

The Gold foil electrode is extremely flexible. Careless handling will produce discontinuities in the recording surface, resulting in electrical instability and high noise levels.
Before using the electrodes as multi-use devices, it is strongly recommended that specialist local opinion is sought.
After use the electrode should be cleaned immediately. Any deposits of mucous or other resi¬due present on the electrode should be removed by gently wiping the electrode surface with a moist tissue or alcohol swab. The following cleaning agents have been found to be satisfac¬tory. Ethyl Alcohol 95% [1], Dexit? [2], Glutaraldehyde 2% (Cidex) [2], or Sodium hyperchlorite solu¬tion (1,000 parts per 1,000,000 available chlorine) [3]. (It is strongly recommended that specialist opinion is sought regarding local rules on cleaning and sterilisation). The electrode should be immersed in the cleaning agent for 10 to 15 minutes, (alcohol) (or manufactures recommended times for other agents), and rinsed in free flowing sterile water. After clean¬ing, the electrode should be stored on the mounting card using a fresh piece of tape. Care must be taken to keep the recording surface flat to avoid creasing. Autoclaving or Ethylene oxide gas sterilisation is not recommended. It is recommended that the electrodes be stored away from direct sunlight or heat sources.
Periodically test the electrode. Using a digital ohm meter, measure the resistance from the plug to the tip of the electrode, if the resistance is greater than 5 ohms, place the electrode on a flat surface, and apply pressure to the foil / wire junction. If resistance remains above 5 ohms or is unstable on flexing, the electrode should be disposed of.
A slight curve over the last half of the electrode facilitates insertion. The gold surface should be the outer radius of this curve. If this curve disappears it is possible to replace it by gently stroking the foil on the inner radius in the position where the curve is required.

 

Shelf life.

Under normal storage conditions the shelf life of these electrodes is typically twelve months. This can be optimised by storing unused in a cool environment, such as domestic standard refrigerator.

 

Infectious conditions.

It is recommended that the electrode be safely discarded after contact with, or possible contact with any such condition.


 


[1] Current opinion suggests that alcohol is not suitable for use against some viral agents.
[2] Observe handling precautions recommended by the manufacturer, and take care to thoroughly remove all traces of the solution prior to repackaging or reuse.
[3] See [2].

Addendum; These electrodes can be sterilised using the Sterad™ process.
1) Special packaging is required to support the electrode during sterilisation
2) Some reduction in electrode life should be expected.