Whats better scleral buckle or gas bubble for an retinal detachment? does the gas bubble move around?

Depends: Depends on where the tear is, the size of the tear, and the surgeon. Yes the gas bubble will move around, but eventually will dissolve.

It depends: A retinal surgeon may chose to use either or both in a surgery to repair a retinal detachment. Each has pluses and minuses. A scleral buckle can change the shape of the eye, making it more nearsighted. A gas bubble can cause the eye pressure to increase. Gas bubbles move with the eye and will gradually be absorbed by the body.