Canthoplasty refers to surgery on the corner of the eye, not the ear

That is an unusual term, however, it probably is surgery on the ear canal. It could have a blockage that needs repair to improve hearing. The blockage can be trauma, born with it, or something getting placed in the canal inadvertently. Depending on the severity and the surgery required to fix it, it could be an out-patient procedure. Also, depending on the severity, the results of the repair could be excellent.