From ISO13485 definition:
medical device:
any instrument, apparatus, implement, machine, appliance, implant, in vitro reagent or calibrator, software, material or other similar or related article, intended by the manufacturer to be used, alone or in combination, for human beings for one or more of the specific purpose(s) of
diagnosis, prevention, monitoring, treatment or alleviation of disease, (NO, for the light)
diagnosis, monitoring, treatment, alleviation of or compensation for an injury, (NO, for the light)
investigation, replacement, modification, or support of the anatomy or of a physiological process, (NO, for the light)
supporting or sustaining life, (NO, no for the light ... or perhaps ...?)
control of conception, (NO, for the light)
disinfection of medical devices, (NO, for the light)
providing information for medical purposes by means of in vitro examination of specimens derived from the human body, (NO, for the light)
and which does not achieve its primary intended action in or on the human body by pharmacological, immunological or metabolic means, but which may be assisted in its function by such means.
I feel its a NO for all the points of the above definition. Hence Small Sterilized Battery Operated Light is not a medical device ...
The key point is "intended by the manufacturer to be used, alone or in combination, for human beings for one or more of the specific purpose(s) of "
So if the manufacturer of the light wants to term it as a medical device saying that it is supporting or sustaining life in its own right, then he can, and based on his further risk assessment, he can be also sterilize it as you have mentioned.
In which case it will become a single use light and must be disposed after one use ?