The vitreous is the jelly-like material that fills up most of the space inside of an eyeball. As we get older, this jelly-like material starts to dissolve and liquefy. In some cases, some undissolved material ends up floating in this liquid space, and can take the form of different shapes like spots, squiggly lines or cobwebs.
These are floaters. In most cases, although floaters can be annoying and distracting, they are harmless. The brain can even get used to the fact that it’s there and begin to ignore it. However, when you look at a bright light background - like a computer screen, or the sky - it will come back into focus.
In some cases, though, floaters can be a sign of something more serious. Having an occasional floater appear is in most cases a normal occurrence, but if you notice a sudden shower of floaters, or sudden very large floaters accompanied by flashing light, it may be the sign of a retinal tear, in which case you need to see your optometrist or emergency department immediately.
When the retina is torn, the vitreous liquid can leak into the tear and cause the retina to continue to further tear, which leads to a retinal detachment. In these cases, timely diagnosis and treatment is paramount in maintaining good vision.