There are various conditions that can cause muscle twitching. Minor muscle twitching is usually the result of less serious, lifestyle-related causes. More severe muscle twitching, however, is often the result of a serious condition.
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air).
The electrodes measure the electrical activity of the retina in response to light. The information that comes from each electrode is transmitted to a monitor where it is displayed as two types of waves, labeled the A waves and B waves.