I'm 14 and I could see worm-like things in my vision.It's been going on for a few years.They're kinda like clear,segmented lines,often forming some kind of clutch.Their numbers seem to have increased and the sizes of each 'worm' is noticeably larger than usual too.I have been seeing them more frequently.What are these,really?
Do you have migraines and dizziness also? If it is so, then maybe you're having an aura - ocular manifestation of headaches.
Also, your problem can be connected to the floaters. They're natural occurrence caused by proteins which accumulates in jelly part of the eye (called vitreous). Then they cast a shadow on your retina, and consequently you see clear lines in your vision.
Both of these states are connected to the problem with retina so, if you already haven't, visit a doctor. That's the best way to determine what is causing that "worm-like things". If it's any comfort, both aura and floaters are easily treated.