Development of vitreous humor
Look at this scheme - 



As I stated before, vitreous is 99% water and is not an organ itself, thus the "replacement of vitreous" is actually = 99% water re-production and the only organ inside the eye which can perform this - ciliary body.

Consequently, if the vitreous was removed and replaced by gas or saline it will be replaced by aqueous which produced by ciliary body - this process takes 8 weeks to completely replace foreign substance as a gas by aqueous.