While it is true that incidences of myopia are increasing, we don't quite have the evidence to assert that it is due to phone and computer use. Indeed, many studies suggest that the reason might actually be a lack of bright light (i.e. sunlight) and that deliberate exposure to bright light may actually be a good intervention to prevent myopia (see e.g. https://journals.plos.org/plosone/article?id=10.1371/journal..., https://www.nature.com/articles/s41598-018-26635-7, https://iovs.arvojournals.org/article.aspx?articleid=2355431)