An accommodation under the ADA is something that the employer and the employee agree on to allow the employee to work when otherwise the conditions of the job would make it impossible, dangerous, or unproductive for the employee.
The employer is required to offer a reasonable accommodation if one is requested and is possible without undue hardship to the employer. If several reasonable accommodations would serve the purpose, the employer may choose which to offer or accept.
If conditions change so that the accommodation is no longer needed or wanted, or a different accommodation is required, the employee should notify the employer of this, and ask for a different accommodation if one is needed.
There is no special form provided by the government to register, change, or end an accommodation. The employer may have forms for its own records. If so they will be designed and provided by the employer.
The employee is not required to continue using an accommodation that is no longer needed or wanted. In some cases there may even be a duty on the part of the employee to notify the employer and stop using an accommodation if it is no longer justified.
The EEOC emphasizes that the process of reaching (or modifying) an accommodation should be flexible and individual, responsive to the particular circumstances affecting a particular employee not rule-bound.
The employee has no obligation to notify the employer that a treatment might (or might not) in future allow the employee do cease using an agreed accommodation. Once a particular accommodation is in fact no longer needed, then the employee should notify the employer.