Figure 1. Schematic of the Ussing-type diffusion apparatus

The sclera was mounted between the two chambers with the intraocular side of the sclera facing the choroid chamber (8 ml in volume) and the episcleral side facing the episcleral chamber (30 ml in volume). The solutions in both chambers were stirred continuously by magnetic bars and the temperature was maintained at 4 °C in all experiments.