“Permanent and total” disability means that the individual has some permanent physical or mental impairment,
                  disease or loss that substantially precludes him from engaging in useful occupations
                  within his competence, such as holding a job or homemaking. Such impairment may be
                  obvious, such as loss of a limb, or discernable only through medical examination.
               
               Disability as an eligiblity factor is not confined to complete helplessness; on the
                  other hand, it is recognized that, with assistance, services and training, disabled
                  individuals may become self-supporting.