Generic selection criteria for safety and patient benefit [IX]: Evaluation of "feeling of use" of sodium hyaluronate eye drops using the Haptic Skill Logger (HapLog®) wearable sensor for evaluating haptic behaviors.

We compared the pharmaceutical properties, such as surface tension, drop volume, nozzle inner diameter, and force to push the drug product out of the container (squeeze force), of purified sodium hyaluronate eye drops preparations of one brand-name (Hyalein) and 11 generic drugs used for treatment of keratoconjunctiva epithelial disorders, and examined product selection based on the needs of the patient. The surface tension of Nissin (51.0 dyn/cm) and Nitten (52.3 dyn/cm) was significantly lower than that of Hyalein (62.8 dyn/cm), whereas Nitten PF (69.5 dyn/cm) was significantly higher than Hyalein. The drop volume of Tearbalance (42.4 mg), Nissin (43.7 mg), and Nitten (42.7 mg) was significantly lower than that of Hyalein (50.4 mg). We compared the squeeze force using a wearable touch sensor (Haptic Skill Logger: HapLog®) and digital force gauge (DF). The squeeze force of HapLog® showed values of about 1.7- to 3.5-fold higher than that of DF. Moreover, the squeeze force of Eyecare (34.0 N), Kyorin (35.4 N), and Nitten PF (44.3 N) by HapLog® was significantly higher than that of Hyalein (10.5 N). In contrast, the squeeze force of Kyorin (20.8 N) and Nitten PF (25.0 N) by DF was significantly higher than that of Hyalein (12.2 N). Two questionnaire surveys on the feeling of instillation of eye drops revealed a strong negative correlation between feeling of use and squeeze force.