The question arises as to whether it is permitted to wear Ace bandages, casts or slings into the public domain without an Eruv. The Halacha is that these are considered a "Tachshit" (ornament) for the person who needs it, and therefore, it is permitted. There is a separate issue of the Halachot of applying bandages and creams on Shabbat.
Hearing aids are also a "Tachshit" for their user and may be worn. The hearing aids are usually fastened properly, and therefore, there is no concern that they may fall off and be carried in the public domain.
The Halacha also mentions a case of someone who was bound in chains. If they cannot be removed, it is permitted to "carry" them in the public domain.
It is permitted to wear bandages, casts, slings and hearing aids into a public domain without an Eruv.