Combination of the degree of loss and word recognition. The implant center will determine eligibility. If you are on Medicare they also have criteria.

The requirement is less than 50% speech scores on the AZ Bio sentence tests, less than 40% if you have Medicare. If you do the testing, make sure you only repeat back the words you actually understand. Do not fill in the blanks as this is a hearing test not a "how well you cope with HA's" test.