When entering into a contract of employment, an individual who has suffered the loss or loss of use of a hand, arm, foot, leg, or eye may waive any right to compensation to which the covered employee would be entitled because of the existing permanent partial disability in the event of a subsequent accidental personal injury or occupational disease. For a waiver under subsection (a) of this section to be effective, the waiver shall: be made in writing, as part of the contract of employment or as a separate instrument; plainly describe the existing permanent partial disability; and be executed by the employee: with knowledge of its contents; and before the occurrence of an accidental personal injury or occupational disease on which a claim is based. If a covered employee who has executed a waiver in accordance with this section suffers an additional accidental personal injury or occupational disease, the covered employee is entitled to compensation for a disability resulting solely from the additional injury or occupational disease.