Myopia, or nearsightedness, is also a very common eye condition. People with myopia find it difficult to see people and objects at a distance. Myopia occurs when the images that enter the eye focus in front of the retina. In many cases, the eyeball is too long and so the focal point of light falls in front of the retina. The cause of myopia is not precisely known, but it may be caused by a combination of environment and genes. The prevalence of myopia is increasing worldwide, and seems to be more common in industrialized countries. Environmental influences are likely of greater impact than family history. Family history may define a risk to an environmental factor, for instance. People with myopia are at higher risk for some eye diseases, such as retinal detachment, retinal degeneration, glaucoma and certain forms of cataract. The blurred vision from myopia can be corrected with glasses, contact lenses, or refractive surgery, but these treatments are not known to reduce the risks of future eye disease.