Inclusion Criteria:  VDT workers as defined by the Italian law (>20 hours a week on PC); in the control group patients no VDT workers. VDT workers at the Foundation or VDT accessing to the general service of the Clinic for a routine visit (VDT group) patients, not working at VDT, accessing to the "general service" of the eye clinic to perform a routine visit will be asked to participate the study (control group) no ocular surgery in the preceding 6 months written consent to participate to study procedures and personal data utilization in an encoded form  Exclusion Criteria:  ocular surgery in the preceding 6 months patients unable to respond to questionnaire