20 C.F.R. § 702.601

(a) Time of injury. For purposes of this subpart and with respect to an occupational disease which does not immediately result in death or disability, the time of injury shall be deemed to be the date on which the employee or claimant becomes aware, or in the exercise of reasonable diligence or by reason of medical advice should have been aware, of the relationship between the employment, the disease, and the death or disability.

(b) Disability. With regard to an occupational disease for which the time of injury, as defined in § 702.601(a), occurs after the employee was retired, disability shall mean permanent impairment as determined according to the Guides to the Evaluation of Permanent Impairment which is prepared and modified from time-to-time by the American Medical Association, using the most currently revised edition of this publication. If this guide does not evaluate the impairment, other professionally recognized standards may be utilized. The disability described in this paragraph shall be limited to permanent partial disability. For that reason they are not subject to adjustments under section 10(f) of the Act, 33 U.S.C. 910(f).

(c) Retirement. For purposes of this subpart, retirement shall mean that the claimant, or decedent in cases involving survivor's benefits, has voluntarily withdrawn from the workforce and that there is no realistic expectation that such person will return to the workforce.