We hear this kind of story several times every day at Skyvsion. Bright flashing lights somewhere in the side of your vision that last for minutes to hours...sometimes like lightening bolts and sometimes just like a shower of stars. I time a great big floaty thing appears. It can be any shape but it often seems like a spider web that drifts in and out of view. You've had a posterior vitreal detachment!
A what?! What kind of detachment?
Remember the blog post about floaters? The vitreous jelly shrinks as we get older, and sometimes it actually shrinks to the point that it separates from the back of the eye. The back of the jelly, the part that was attached to the back of the eye, is now free floating, and it becomes dense and thick. Your big floater!
When the vitreous jelly pulls off it tugs on the retina putting traction or pull on the inner retina (the film on the inside of your eye). Now, the retina can only respond to ANY kind of stimulation in just one way. Bite it, scrratch it, tickle it, pull on it, or shine light on it, the retina will give off a sensation as if it has seen light. So when the vitreous jelly contracts and pulls off you get flashing lights!
HERE to see an eyemaginations video on vitreous detachments, and we'll talk some about retinal detachments another time.