Microscope laser
The microscope laser or miniature laser was a specialized medical instrument designed for middle ear healing. 

Nurse Chapel reminded Dr. McCoy of this device when the miniaturized Hikaru Sulu broke his leg in 2269 and the normal bone-knitting laser technology could not be used. When attempting (successfully) to retrieve it, she fell into an aquarium and was rescued by Kirk. 

While being healed by the device, Sulu noted that he could feel his bone . ()

Medical equipment