If you've never experienced floaters in your vision, you are truly in the minority. Eye floaters are usually caused by age-related changes within the vitreous, or jelly-like substance inside your eye. Yes, that means that the material that causes floaters is actually inside your eye, and your eyes must be open for you to notice them. As the vitreous ages, it begins to liquify and begins to clump together microscopic fibers within your eyeball. These small clumps cast small shadows on your retina in the very back of your eye, and these small shadows are what you know as floaters. They'll often look like small dots, strands, or squiggly lines.
Floaters can be particularly annoying because they move around any time your eye moves. You'll also tend to notice them much more on a sunny day with a bright blue sky, or if you're looking at a white piece of paper. This is because those shadows are dark, and the darkness is much easier to notice in bright light!
So what exactly causes them? Like we stated earlier, floaters can simply be due to aging, and this is the most common reason for them. Floaters due to aging are usually not anything to worry about and can just be monitored at your yearly eye exam. However, there are quite a few pathological reasons for floaters. If you ever see large, black, or red floaters, or new floaters that you've never noticed before, it's worth getting them checked out. These could be a sign of a retinal tear or detachment, meaning that the sensitive film of your eye is torn or pulling away from the back of the eye. When this happens, dark pigment (and sometimes blood) is released into the vitreous, causing a swarm of new floaters. A retinal detachment may even look like a curtain coming down over your vision! These are scary circumstances and are ocular emergencies, but these instances are rare.
One more common cause of floaters is a posterior vitreous detachment (PVD). Very common over the age of 65, PVDs occur when sections of the vitreous pull away from the back of the eye. This is different from a retinal detachment, much less serious, and usually is not a cause for concern. Over time, a PVD floater will settle down and you may not notice it at all after a few weeks. Other causes of floaters may include uveitis (inflammation in the back of the eye), infection, hemorrhages, and injury to the eye.