At this age it is very uncommon in normal eye , you may be myopic in which vitreous degeneration starts at early age , you should consult retina specialist & if there is no no retinal pathology , you should try to ignore it . You should take balanced diet along with lots of green vegetables as well as seasonal fruifs rich in beta carotene eg mango plenty in this season

Hello A. Retinal detachment after vitreous detachment is less common B. There is no sure shot way to prevent retinal detachment C. Having said that, decrease movement of eye and head