.
By C. Jake Williams. March 14, 2008
. Email Jake - Email this
Have you ever closed your eyes and seen those expanding or contracting alternating dark and light circles?
Recently after an extended stay in my brightly lit front room, I closed my eyes in my dark room. I saw the circles and they were contracting to the center of my vision. Fast at first, I noticed the rate the circles were contracting began to slow over time, then I had an idea.
I theorized that the circles in my vision were caused by my pupils dilating to allow more light to reach my retina.
Like any good scientist, I tried to imagine a test which could disprove my theory.
I opened my eyes to note how clearly I could see in the dark at that moment. Check.
I closed my eyes again and concentrated on the idea of a well-lit room. Check.
After a few minutes the circles were expanding in my vision instead of contracting, just as I had hoped. If contracting circles were caused by my pupils enlargening to allow in more light, it seems reasonable to expect expanding circles to result from the pupil shrinking to allow less light, and shrinking pupils is exactly what occurs when we move from poorly lit areas to the well lit.
One last part of the test remained: I needed to open my eyes to gauge if my night vision had improved over time as normally occurs in a dark room or if I had truly tricked my pupils into acting as if a lamp was illuminated.
I opened and couldn't see a thing; my night vision had deteriorated.
I conclude that vision circles are the result of pupil dilation.
You were there.