Sometimes, when we find ourselves daydreaming or staring into the air, we might notice some squiggly lines or funny shapes floating about, and no matter where we look, they seem to be moving along with our eyes. There are different names for these shapes: eye floaters, vitreous floaters, and Muscae volitantes (lit. "flying flies"), but its scientific term is myodesopsia.
These floaters appear in our vision when blood or other cells that got into the vitreous humor - the transparent, gel-like substance filling the space between the lens and the retina - block light passing through the eye, casting shadows onto the retina.
Unlike the aqueous humor, the liquid substance found between the iris and the cornea, the vitreous humor never washes out or gets replenished. So, whatever gets into the vitreous, stays there for the rest of our lives. Meaning, if you are seeing eye floaters right now, you will continue seeing them until death do you part.
For most people, these eye floaters present no issues. We sometimes take notice of them until our attention drifts elsewhere. Others, however, might experience too many floaters clouding their vision, but this is more common in older people.
A sudden increase in floaters may be a sign that someone is suffering from posterior vitreous detachmant (PVD), when the vitreous becomes separated from the retina. This poses the risk of retinal tearing which can cause blindness.
Several treatments are available, but even the standard procedure, a vitrectomy, is still considered risky and must only be used as a last resort.
(Image credit: Acdx/Wikimedia Commons)