In vitro techniques are commonly used in eye research and they are valuable tools with several benefits like their modest price, well controlled test environment and the relatively simple interpretation of the results. They are after their validation usually relatively easily and quickly performed and in most cases suitable for automated analyses. In many cases their use can replace in vivo studies with experimental animals and thus they are ethically sustainable. By using valid in vitro techniques it is also possible to simplify the research frame from very complex in vitro situation and to set more specified hypothesis. There are, however, several drawbacks in the use of in vitro techniques. The results of them should be analyzed critically and the validity of the used in vitro technique should be rechecked on the basis of the new knowledge. It should also be kept in mind that an in vitro technique is usually valid for one specific cell mechanism and could be unacceptable for another.