Is nearsightedness genetic or from something else.?

The issue if nearsightedness is purely genetic or if it is the result of tissue alterations influenced by environmental factors is greatly debated! Many scientists now argue that both factors can be involved in developing myopia/nearsightedness.
Nearsightedness has been linked to several different genes and it has been found to be predominately genetic. It is still not fully understood what causes people genetically susceptible to myopia to develop it while others do not. That is where the environmental factors apparently come into play. This issue is very complex and as of now there is no concrete evidence to actually prove any theory 100 percent. The only thing that has been proven is that genes are involved in developing myopia and many factors are involved! The occurrence of myopia has been increasing in many places and it is thought that lifestyle changes like focusing on close objects, such as computer screens, mobile phones and books may have some involvement in causing myopia in those people genetically susceptible during visual development.
"A study of 506 pairs of twins (both identical and non-identical) confirmed an earlier study by the same group that genes are by far the most important factor with a heritability of 89% - environmental factors only accounted for 11%. "
Research is still not conclusive on this matter so as it stands nearsightedness is predominately genetic, since even small deviations from normal structure cause significant refractive errors, it may be difficult to single out any specific genetic or environmental factor as their cause.
"Only 6%-15% of children with myopia come from families in which neither parent is myopic. In families with one myopic parent, 23%-40% of the children develop myopia. If both parents are myopic, the rate rises to 33%-60% for their children. One American study found that children with two myopic parents are 6.42 times as likely to develop myopia themselves as children with only one or no myopic parents. The precise interplay of genetic and environmental factors in these family patterns, however, is not yet known."


I am interested to see how this unfolds with further research in the future! Check out the links for more info !

It's primarily genetic. If your mom and/or dad has bad eyesight, there's a good chance you will too. But, your parents could both have bad eyesight and carry genes for good eyesight and pass them on to you. Bad eyesight could come from outside factors too (even if you have genes for good eyesight), for example from straining your eyes over time through the work you do (excessive exposure to high-intensity light, reading print that is too small, etc.) and/or having a poor diet lacking nutrients that your eyes need to stay healthy. But, outside factors often have to occur over an extended period of time (years) to contribute significantly to bad eyesight, whereas with genetics, you have what you have. Best wishes!