This study will evaluate the safety and effectiveness of a new formulation of triamcinolone acetonide for the treatment of retinal blood vessel disorders. Triamcinolone is a steroid drug that decreases inflammation and scarring and is routinely used to treat eye inflammation or swelling. The commercially available form of this drug is associated with potentially harmful side effects thought to be due to preservatives in the preparation. This study will use a formulation that does not contain these potentially harmful preservatives. Preliminary findings from other studies suggest that injection of steroids in the eye can reduce retinal thickening and improve vision. However, they may also cause mild discomfort and lead to vision-threatening conditions. The effects of the drug on the conditions under study in this protocol are not known.