heya ... im 17 and i saw my floaters 1st time when i had an english lesson 4 yeahrs ago .. they were rather small and after i was told and understood what caused these annoying dots and lines i dismissed em .. it was possible cos i just saw them on white walls and sky ..
after my summer holidays i discovered 3 real big floaters .. lines with knotted dots and cobwebs ..

and my suggestion is
the UV-radiation is THE main aggravationing factor for the development of floaters ....
i suppose this cos i used to sit 5-7 hours/day
and 12+ hours/day at weekends in front of the pc

and if u know the braun tube in my crt monitor works like this:
electrons are being shot on a phosphorfilm which causes the colours we see .. and additional UV-radiation arises..

and the fact that my eyes got heavily bombed with these uv-radiation during the summer holidays and i saw the big floaters at the end of these leads me to the guess that UV causes the appearance of floaters