In general, cochlear implants are used to allow deaf people to hear. Although many people who are "hearing impaired" or "hard of hearing" believe they are deaf, "deaf" is generally defined as having more than a 90 dB HL hearing loss. In other words, if someone can benefit from hearing aids, that is usually the treatment of choice. However, if they are not able to satisfactorily benefit from hearing aids, cochlear implants are often a surgical option. Additionally, because of the excellent progress made with cochlear implants over then last two decades, sometimes, people with severe hearing loss (defined as worse than 70 dB HL) might be implanted and sometimes hearing aids are combined with cochlear implants in particular situations. Cochlear implants and hearing aids can be combined in one ear, and sometimes a cochlear implant is placed on one ear while a hearing aid is worn on the other. The best way to determine candidacy for a cochlear implant, is to undergo a "cochlear implant evaluation" at a cochlear implant center.