The Japan MD classification is a 3 -tier system...general, controlled and highly-controlled, with general being the low risk and highly-controlled, the high risk category.
General MD present minimal potential harm to the user. they are regarded as low-risk and include most non-invasive products, certain invasive products, and reusable surgical instruments. examples include wheelchairs, scalpels, dental drills and wound mgt systems.
Controlled MD are generally diagnostic devices and include both invasive and non-invasive products and medical devices for short-term use. Ex: wound dressings; products that channel and store blood for administration into the body; surgically invasive devices for transient or short-term use; most active therapeutic devices that adminster or exchange energy; and active diagnostic devices that supply energy absorbed by the body(otherthan illumination).
Highly Controlled MD: --are regarded as posing a medium-to-high risk to the user. Devices in this class are used to diagnose or monitor, come in contact with the circulatory or central nervous system, or incorporate medicinal products. Examples include condoms, radiological equipment, surgically invasive devices, blood bags, vascular grafts, bone cements that contain antibiotics, and implantable defibrillators.
I hope this helps.
Regards,
Sreenu