The biggest disadvantage of conventional ophtalmic forumulations lies in their low bioavailability which is the restricted due to the ocular barriers in the anterior parts of the eye. Nanoemulsions are a drug delivery system characterized by the droplets with a droplet size in the nanometer range and with the great potential to overcome these barriers. The goal of this research was to prepare O/W type nanoemulsions containing castor oil and four types of non-ionic surfactants using the microfluidization method. The average droplet size, polydispersity index as well as the zeta-potential of nanoemulsions were determined. The results obtained suggested the increase in surfactant quantity causes a decrease in internal phase droplet size. Surfactant quantities of 0,5% and 1% (of total emulsion mass) showed to be insufficient for preparing nanoemulsions of adequate properties. With growth of the surfactant mass percentage, a plateau was noticed at a concentration of around 4% and droplet sizes of approximately 250 – 200 nm. Further growth of surfactant mass percentage would not result in ensuring significantly smaller droplet sizes. Nanoemulsions containing Cremophor EL as a surfactant proved to have droplets of the smallest average size. The smallest polydispersity index (PDI) values were observed in nanoemulsions containing Pluronic F68 as a surfactant. Zeta-potential measurements of all formulations indicate the existence of low negative charge at the surface of internal phase droplets. This charge originates from free fatty acids that come from castor oil. All of the nanoemulsions were shown to be stable for 10 days, but there was an increase in PDI values noticed after remeasuring the properties of nanoemusions containing Polysorbate 80, Polysorbate 60 and Cremophor EL. Polydispersity of these formulations could result in nanoemulsion destabilisation over a longer period of time.