It shall be incumbent upon the employer to establish that the employer had reached an informed conclusion prior to the occurrence of the subsequent injury or occupational disease that the preexisting impairment is permanent and is likely to be a hindrance or obstacle to employment or reemployment. Where, however, the employer establishes knowledge of the preexisting permanent impairment prior to the subsequent injury, there shall be a presumption that the employer considered the condition to be permanent and to be, or likely to be, a hindrance or obstacle to employment where the condition is one of the following:

(1) Epilepsy;

(2) Diabetes;

(3) Arthritis which is an obstacle or hindrance to employment or reemployment;

(4) Amputated foot, leg, arm, or hand;

(5) Loss of sight of one or both eyes or a partial loss of uncorrected vision of more than 75 percent bilaterally;

(6) Residual disability from poliomyelitis;

(7) Cerebral palsy;

(8) Multiple sclerosis;

(9) Parkinson's disease;

(10) Cardiovascular disorders;

(11) Tuberculosis;

(12) Mental retardation, provided the employee's intelligence quotient is such that he falls within the lowest 2 percent of the general population; provided, however, that it shall not be necessary for the employer to know the employee's actual intelligence quotient or actual relative ranking in relation to the intelligence quotient of the general population;

(13) Psychoneurotic disability following confinement for treatment in a recognized medical or mental institution for a period in excess of six months;

(14) Hemophilia;

(15) Sickle cell anemia;

(16) Chronic osteomyelitis;

(17) Ankylosis of major weight-bearing joints;

(18) Hyperinsulism;

(19) Muscular dystrophy; (20) Total occupational loss of hearing as defined in Code Section 34-9-264;

(21) Compressed air sequelae;

(22) Ruptured intervertebral disc; or

(23) Any permanent condition which, prior to the occurrence of the subsequent injury, constitutes a 20 percent impairment of a foot, leg, hand, or arm, or of the body as a whole.