Ocular fluorescein kinetics before and after vitrectomy on swine

Purpose: To study the quantitative effects of vitrectomy on fluorescein transport kinetics across the ocular barriers. Methods: Thirty-six domestic swine were used in this study. Twenty anesthetized swine were given a standardized fluorescein intravenous injection immediately after unilateral vitrectomy. This was followed by one single central sample aspiration from the vitreous and the anterior chamber of both eyes in individual animals at increasing intervals up to 24 h after the injection. Fluorescein concentrations in the samples were determined by high-pressure liquid chromatography HPLC. Eight swine underwent unilateral vitrectomy followed by anterior chamber and vitreous fluorophotometry on both eyes I month later. The fluorescein concentrations determined using this method were followed for 24 h. Similar examinations were performed in a control group of eight swine that did not undergo vitrectomy. Anterior chamber, vitreous, and plasma fluorescein concentration/time courses were analyzed kinetically by iterative nonlinear regression analysis. Results: The barrier surrounding the anterior chamber of the eye was immediately impaired after vitrectomy, as evidenced by an increased area under the fluorescein concentration versus time curve, but the transport kinetics were restored within I month after surgery. The blood-retinal barrier was, however, persistently altered following vitrectomy. Transport rate and extent of drug penetration into the vitreous were increased, while drug elimination from the vitreous remained unchanged. Conclusion: Vitrectomy led to persistent kinetic fluorescein transport changes in the blood-retinal barrier resulting in faster and increased drug penetration to the vitreous. whereas similar alterations in the anterior chamber barrier transport were only transitory.