In the present study, Cyclosporine A (CsA) was successfully incorporated into cationic solid lipid nanoparticles (SLN) for ocular application. Physicochemical characterizations of SLNs were analysed in detail during the storage period of 6 months. Due to the better characteristics like smaller particle size (248.00 +/- 0.33 nm) with narrow size distribution (PI = 0.25 +/- 0.00), high zeta potential (50.30 +/- 0.78 mV) and more stable lipid structure, Dynasan (R) 116 structured FD4 (0.1% CsA) formulation was chosen for in vivo studies. Sheep were used in in vivo studies and 200 mu L of formulation was applied to sheep' eyes (n = 6) under veterinarian supervision. Samples were collected at pre-determined time intervals and were analysed by enzyme immune assay (EIA). CsA could be detected in both aqueous and vitreous humour samples for 48 h showing the ocular penetration of formulation. Release profiles were not decreased during 48 h indicating controlled and prolonged release of active agent from positively charged SLN formulations due to increased residence time in eyes. Similarities in CsA concentration data showed that inter-individual variance did not influence the ocular penetration of CsA when formulated as SLN.