Difference in clearance of intravitreal triamcinolone acetonide between vitrectomized and nonvitrectomized eyes

Purpose: To study the difference in clearance of intravitreal triamcinolone acetonide quantitatively between vitrectomized and nonvitrectomized eyes. Methods: Eighty-four eyes of 42 rabbits were divided in 2 groups: 42 right eyes underwent standard pars plana vitrectomy (vitrectomized group), and 42 left eyes were not operated on (nonvitrectomized group). All eyes received intravitreal injections with 0.1 mL (0.3 mg) of triamcinolone acetonide. Every 12 eyes were obtained by killing 6 rabbits 1, 2, 4, 7, 12, 20, or 30 days after intravitreal injection. Each eye was enucleated and immediately frozen at -70 degrees C. The frozen vitreous was prepared for measuring the concentration of triamcinolone acetonide. Triamcinolone acetonide was quantified by high-performance liquid chromatography and ultraviolet absorbance detection. Results: After 30 days, triamcinolone acetonide was detected only in 1 eye (0.22 mu g/mL) in the vitrectomized group compared with 4 of 6 eyes (0.92 +/- 1.25 mu g/mL) in the nonvitrectomized group. The coefficient of logarithmic regression was -0.12 in the vitrectomized group and -0.08 in the nonvitrectomized group. Triamcinolone acetonide decreased 1.5 times more rapidly in the vitrectomized group than in the nonvitrectomized group. The half-life of triamcinolone acetonide was 1.57 days in the vitrectomized group and 2.89 days in the nonvitrectomized group. Conclusion: Intravitreal triamcinolone acetonide decreases more rapidly in the vitrectomized eye than in the nonvitrectomized eye. Therefore, the faster clearance of intravitreal triamcinolone acetonide must be considered when planning intravitreal injection of triamcinolone acetonide in the vitrectomized eye.