Objectives: The long treatment duration of glaucoma and multiple drug use have decreased patient adherence to anti-glaucoma drugs. This has prompted the recent marketing of a combination drug, Xalacom ® Combination Eye Drops (hereinafter referred to as the original drug), and its generic drugs (3 generics). In this study, we compared these eye drops from a pharmaceutical viewpoint,conducted research on usability, and evaluated the selection criteria for generics.Methods: The viscosity and pH of the original drug and its generics were measured. The total number of drops per container, mean mass per drop, and the squeeze force needed for one drop of individual eye drops were measured using a digital force gauge. In addition, a questionnaire survey on the usability of each eye drop was conducted in patients.Results: The total number of drops in the contain of the original drug and generics tested almost the same. The mean mass per drop of generics from two companies was significantly lower than that of the original drug, and the squeeze force of the generic from one company was significantly lower than that of the original drug. The usability of the containers some generics was significantly higher than that of the original drug.Conclusion: No difference was observed in the total number of available drops between the original drug and generics. However,differences in squeeze force and usability were observed between the original drug and generics and among the generics. This information should preferably be described in the interview form, patient instruction manual, etc. for providing medication instructions to pharmacists. All products investigated in this study contained more than 100 drops in the containers. The expiration date of tested eye drops after opening is about one month. Reducing the volume of filling into a container may be contribute to the medical economy and avoid the risk of microbial contamination.