Vitreous is a gel-like substance that fills the eyeball. As we age the vitreous shrinks and comes gradually off of the retina.
Shortsighted people can get vitreous detachment earlier in life. The symptoms include floaters (“cobwebs”) that seem to affect the field of vision.
Occasionally the vitreous is strongly attached to some parts of the retina and the pulling effect causes flashing lights. This pull on the retina can rarely lead to retinal breaks that require urgent laser treatment to prevent a retinal detachment. Symptoms of vitreous detachment settle down with time and in most cases observation only is recommended.