A medical device enables a user to bend it into a shape to suit a specific patient need or to orient efficiently the medical device for use. The gate electrode includes a transparent conductive film and an opaque conductive film, and the transparent conductive film is between the channel region and the opaque conductive film. The optical fibre plug includes a projecting ferrule and along an axis of this ferrule a first optical fibre. The first prism sheet concentrates light supplied from a lamp to output the concentrated light.