Vitrectomy is a surgical procedure used for the treatment of sever vitreous hemorrhage. It is not clear whether it is better to perform this procedure on an eye immediately after the hemorrhage appears or to wait a period of time, say 1 year. The procedure carries some risk and in some eyes the hemorrhage spontaneously disappears. A randomized trial is planned of 60 eyes at a major clinic. An equal number of eyes will be assigned to "early" and "late" vitrectomy. For some patients a hemorrhage appears in both eyes and for these patients the investigators have decided that each patient will receive both treatments (one to each eye) if they consent. Such patients are ineligible unless they consent to receiving both treatments. In other patients a hemorrhage appears in only one eye and for these patients the single eye will be assigned to one of the treatments. Prepare the randomization schedule(s) for this study. Carefully explain each step of your procedure for generating schedules and why you chose to do it the way you did.