“…The incidence of retinoblastoma is related to the interaction of many factors, for example, where the parents live in city, the presence of pets during pregnancy mainly cat and dog, and exposure to hazardous chemicals from the father six months before pregnancy (paint, leather equipment, decoration, electronic accessories, benzene, formaldehyde and other heavy metals. 16 Cases of nonheritable retinoblastoma have unilateral tumors, unlike heritable retinoblastoma, which often develops bilaterally and multifocally. The most cases about two-thirds of all cases were unilateral retinoblastoma.…”