According to a survey by the German Forsa Institute of 1,001 people aged between 30 and 65, two-thirds of the respondents suffered from digital vision stress after using smartphones or tablets. The Forsa study, which was commissioned by Optiker Bode, the German chain of optical stores, found that people aged between 30 and 39 were most concerned. Sixty percent of the male respondents and 64 percent of female respondents suffered regularly from digital vision stress.