The eye is well-protected by several anatomical and physiological barriers which also pose significant challenges for ocular drug delivery. Even though ocular pharmacokinetics and the permeability of eye’s important anatomical barriers, such as the cornea and the blood-ocular barriers, have been thoroughly investigated, the significance of active transport in the eye is not completely understood. It is known that several drug transporters are also expressed in ocular tissues, but scientific information on this area is still dispersed and incomplete. The aim of the literature review in this master’s thesis was to compile the current knowledge on the expression and activity of OATP transporters (SLCO; organic anion transporting polypeptides) in cornea and in the blood-ocular barriers. Main principles of ocular pharmacokinetics and common methods for studying transporters are also discussed. The experimental part in this thesis is focused on retinal pigment epithelium (RPE) which is a substructure of the blood-retinal barrier. The transporters of the RPE were studied with three different RPE model systems: human RPE cell line (ARPE-19), fetal primary RPE cells (hfRPE; human fetal retinal pigment epithelium) and ocular tissues of the rabbit. In detail, transporter expression was studied with proteomics from the plasma membrane of isolated rabbit RPE and transporter activity by cellular uptake assays (ARPE-19, hfRPE) in vitro and permeability experiments with rabbit RPE-choroid-sclera ex vivo. As with the literature part, the experimental work was mainly focused on the human and rabbit OATP/Oatp transporters. In this thesis, ten important drug transporters were detected from the rabbit RPE. No significant OATP/Oatp activity was observed either in vitro or ex vivo experiments so these transporters seem not to have a great role in the disposition of their substrates in the studied RPE models. However, signs of other active transport were evident especially in the ARPE-19 cell line, in which significant accumulation of the tested substrate, 4’,5’-dibromofluorescein (DBF), was noted in the presence of several inhibitors. The phenomenon was suspected to result from efflux inhibition, but the responsible transporters could not be unequivocally detected. In conclusion, the findings of this thesis highlight the importance of conducting further research on the transporters of the RPE and choosing a suitable RPE model case-by-case for each study. With the compounds used in this thesis, ARPE-19 and hfRPE cells showed marked differences in efflux activity while the small size and fragile structure of the posterior ocular tissues of the rabbit caused notable difficulties in performing the transporter studies.