Disability insurance benefits
(a) Disability insurance benefits. An individual who has attained age 55 and who meets the definition of disability for disability insurance benefits purposes based on statutory blindness, as defined in 404.1581, may be entitled to disability insurance benefits for months in which he is engaged in certain types of substantial gainful activity. No payment, however, may be made to the individual or to beneficiaries entitled to benefits on his earnings record for any month in which such individual engages in any type of substantial gainful activity.