I have had two vitrectomies, one for the initial repair and another to remove the silicone oil injected during the first to hold down the retina. In both cases, I could see light immediately and could see as soon as the dressing was removed. Your results could well vary from this but you need to be asking your opthalmologist as he knows the particulars of your case and you are paying for his knowledge so get what you pay for. Don't wait around until the next appointment...call him.
Vitrectomies are performed for a number of conditions (e.g., macular holes, retinal detachments, epiretinal membranes.) Recovery time is very much related to the reason for the surgery.