Abstract
PURPOSE: The aim of this study was to determine the scleral permeability of a commercially available version of 2',7'-difluorofluorescein (OG) and compare it to that of sodium fluorescein (NaF). METHODS: Both in vitro and in vivo experiments were performed. For the ex vivo experiment, a Lucite block perfusion chamber with human donor sclera was used. Two hundred microliters (200 microL) of 2.5 mg/ml OG or NaF was placed in the donor chamber. The OG and NaF concentration that diffused across the sclera was measured every 2 h for 24 h by fluorometry, and the fluorescence in the sclera was examined by fluorescent microscopy. In vivo experiments consisted of live rabbits treated with a 0.2-mL subtenon injection of 7.5 mg/ml solution of either OG or NaF in the right eye. Intraocular fluorescence was measured by ocular fluorophotometry. RESULTS: The scleral permeability coefficient (K(trans)) of OG was 3.93 +/- 1.01 x 10(-7) cm/sec and that of NaF was 4.41 +/- 1.32 x 10(-7) cm/s. Both OG and NaF were visible throughout the sclera after 24 hours. Peak vitreous concentration after subtenon injection in rabbits was 6.48 +/- 2.65 ng/mL of OG at 2 min and 47.15 +/- 13.3 ng/mL of NaF at 10 min. CONCLUSIONS: OG was able to diffuse across the sclera and thus could be potentially useful as a fluorescent tag for intraocular drug delivery studies. However, its permeability was substantially less than that of NaF.