Use of tablet, smartphone and myopia: where is the evidence?

where is the evidence of the relationship between the use of tablet or smartphone and myopia? The answer is nowhere, because there is no scientific evidence on this relationship. We are very interested in underlining that the improper use of tablet and smartphone could contributeto a negative evolution of myopia, especially if preventive measure are not respected, including the use of corrective lenses. And we must not forget that for severe cases ofmyopia, high technological procedures are needed