What are eye floaters and are they dangerous?

The answer

Eye floaters are shadows cast on the retina by small clumps of collagen fibers floating in the vitreous humor, the gel-like substance that fills the eye. The vitreous is about 99% water and 1% collagen and hyaluronic acid. With age, the vitreous gradually liquefies and its collagen fibers clump together, creating more visible floaters. Most floaters are harmless, but a sudden shower of new floaters, especially accompanied by flashing lights or a curtain-like shadow in peripheral vision, can indicate a posterior vitreous detachment or retinal tear, which is a medical emergency requiring immediate evaluation. The brain typically learns to ignore persistent floaters through neural adaptation, essentially filtering them from conscious perception. For severely bothersome cases, laser vitreolysis can break up large floaters, and vitrectomy surgery can remove the vitreous entirely, replacing it with saline solution.