No, halos are not only caused by cataracts. I am 24 and developed literally hundreds of floaters in both my eyes over night when I was 21. I have 20/20 vision and doctors can not explain why it happened to me, but the vitreous in both my eyes spontaneously separated from my retinas simultaneously. Floaters will always be a real nuisance, but I am putting up with them until the vitrectomy is improved.
Halos are a very common problem for floater sufferers. The distortions are caused by light diffracting through the floater debris before reaching your retinas. I know, if I ever drive at night, large halos develop around headlights and traffic lights. Of course driving during the day can be even worse with all the dark floaters obscuring my vision
Chuzzlewit, have you been to FloaterTalk yet? It's the main forum that floater sufferers visit.
Take care, Justin