Are circle lenses hazardous for your eyes?

I never had contacts before, I haven't even talked about getting contacts with my eye doctor although I do wear gles [ -2.25 and -2.75? I don't even know the perscription of my eyes D; ] But I was thinking of getting circle lenses because my eyes are rather small, so what do circle lenses do to your eyes? Are they the same as normal colored contacts? Would it be weird if I were to wear colored circle lenses, non perscripted, under my gles?