Pulmonary Oxygen Toxicity (PO) and Central Nervous System Toxicity (CNS)
Oxygen toxicity can cause seizures and spasms. That implies to me that flickering eyes may be a symptom of O2 toxicity, but not a common or likely one. While possible, I'd personally look elsewhere for the cause.
Abnormally slow breathing is a symptom of oxygen toxicity
Partial pressure of oxygen of 1.6 will cause toxicity. If using standard air (roughly 20% O2) this equates to a pressure of 8 bar which is present at 70m. In terms of the percentage of O2 which causes toxicity, it depends on the depth but a partial pressure of 1.6 bar is the toxicity threshold
Argon is nontoxic. But because it takes up space as all gases do it can displace oxygen in the atmosphere and cause hypoxia.
Pulmonary oxygen toxicity is caused by divers exposing themselves to elevated partial pressures of oxygen for long periods of time, and is primarily a concern for technical divers who decompress on oxygen. Pulmonary oxygen toxicity causes a burning sensation in the trachea, coughing, shortness of breath, and eventually lung failure.
Cells resist oxygen toxicity because of the semi permeable membrane. This controls the amount of molecules and what molecules enter the cell.
Oxygen toxicity.
death
The signs and symptoms for oxygen toxicity include changes in vision, nausea, twitching, and dizziness. More serious symptoms can include seizures and possible death.
Systemic toxicity may result from ingestion of iodine containing compounds or mercury compounds.
There is not any exact amount of time that would cause toxicity in a room. However, this is dependent on how large the room is.
Oxygen is very reactive and causes things to oxidize. This includes the genetic material of your cells which is one of the reasons why people get old.