High myopia is a chromosomal recessive disorder, which means that the pair of genes related to myopia are both the causative genes of the disease before it develops; if only one of them is the causative gene and the other is normal, it does not develop but is only a carrier. Thus, the combination of two highly myopic individuals has a 90% or greater chance of developing the disease in their children. A highly myopic person who combines with a carrier of the myopia gene may have half of his or her children be highly myopic. In contrast, a highly myopic person who combines with a person with normal vision or low to moderate myopia has a 10% chance of having a child with high myopia. This is because about 20% of our general population are carriers of the myopia gene.