For most people, floaters occur as they grow older. The vitreous humor thickens and clumps as we age, and floaters result from the clumped vitreous gel. Sometimes pregnant women see spots caused by little bits of protein trapped within the eye. Eye injury or breakdown of the vitreous humor may also cause spots and floaters.
When people reach middle age, the vitreous gel may start to thicken or shrink, forming clumps or strands inside the eye. The vitreous gel pulls away from the back wall of the eye, causing a posterior vitreous detachment. It is a common cause of floaters, and it is more common for people who:
have undergone cataract operations;
have had YAG laser surgery of the eye;
have had inflammation inside the eye.