A while back, we explained what those weird floating things are that you sometimes see in your vision; little blobs of tissue, protein clumps, and red blood cells.

But eyes do not just reserve being little weirdos for when they are open. When you close your eyes or open them in a very dark room, you might sometimes notice different patterns and swirls of colors, or even flashes. Some visual disturbances can be caused by medical conditions, and if you experience persistent disturbances you may want to visit a medical professional. But most people experience harmless visual hallucinations with their eyes closed, which are the result of the normal functioning of your eyes.

These are called "phosphenes", which are sensations of light experienced by people when there is no light to cause them.

"Our eyes don’t turn off in the dark, but instead they create very weak internal signals that mimic light. These signals are constantly being made by the cells at the back of your eyes," Katrina Schmid, Associate Professor in the School of Optometry and Vision Science at Queensland University of Technology, explained in a piece for The Conversation.

"The swirls and waves we see are made by changes in activity from these cells. The blobs may be coloured because the cells in your eyes that detect colour also show this activity. These signals are transmitted to the brain, and the brain interprets this random activity. Your brain doesn’t know they weren’t produced by real light, so we think we’re seeing coloured lights and patterns that are not there. It’s a kind of illusion!"

While they do occur in healthy individuals, they can also be a sign of retinal issues, such as retina detachment, neurological conditions, or that you've simply been rubbing your eyes too much. You can cause phosphenes if you (accidentally, please don't do it on purpose) apply slight pressure to your eyeball. 

"If what you’re seeing has changed, and the patterns of light become much more noticeable or hang around for longer," Schmid added, "it could indicate a problem".

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current. 

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.