To investigate the characteristics of the clear oil-drop residue observed in the vitreous cavity after intravitreal injection of different brands of triamcinolone acetonide (TA), and to compare this ingredient's effects in those products.

Intravitreal injections of four different brands of triamcinolone acetonide (4 mg/0.1 mL), which are commercially available in Korea, were given to 40 eyes for the treatment of macular edema due to a variety of causes from October 2005 through February 2006. Regular slit-lamp biomicroscopy of fundus had been performed periodically with digital image acquisition equipment after injection of TA for at least two months. We analyzed the characteristics of this residue and compared the number and size of this residue in each product.

Four TA products commercially available in Korea were used, with vehicles composed of preservatives and suspending agents. There were differences between products in respect to ingredients and content, as well as the characteristics of the intravitreal clear oil droplet-like residue.

Each TA product has a variable frequency and variable amounts of clear oil droplet-like residue, which seems to be a component of the vehicle. This variation could generate differences in efficacy, side effects, and retaining duration. It should be verified whether commercial TA products are consistently safe and effective.