I notice with great surprise that the current poll question has caused no reaction on this forum. Most people used both eyes at the same time.

But a few of us have leaned to do different things with each eye all at the same time. It is highly effecient. For example, I can read a book with one eye while the other eye sleeps. Then when that eye wakes up, it can take over the reading so that the other one can get some sleep. No time lost. I can drive with one eye while watching the speedometer with the other, thus avoiding speeding tickets. I use one eye to watch the thread while the other watches the needle. That way I can be sewing while others are still trying to thread the needle. But I can still make my eyes work together. It took me a while to learn, but I am now able to wink with both eyes at the same time.
Howard