High myopia (pathological myopia) is caused by excessive axial elongation that primarily involves the ora-equatorial area and the posterior pole. Peripheral fundus changes and posterior staphyloma formation are ophthalmoscopic evidences of this process. Pathological myopia often accompanied by glaucoma, cataracts, macular degeneration, and retinal detachment, leading to blindness when the damage to the retina is extremely severe. Population and family studies in Chinese have provided evidence for a genetic component to pathologic myopia. Children of myopic parents are more likely to have myopia than are children of nonmyopic parents. The ocular components (axial length, anterior chamber depth, and corneal curvature) and refractive errors of MZ twins are more closely aligned than are those of DZ twins.

Therefore, it is possible to search a potential candidate gene for myopia through the genomic study of pathological myopia.