zahra hashemi dehaghi eye research center, tehran university of medical sciences, tehran, ir iran abbas sheikhtaheri department of health information management, school of health management and information sciences, iran university of medical sciences, tehran, ir iran; department of health information management, school of health management and information sciences, iran university of medical sciences, tehran, ir iran. tel: +98-2188794300, fax: +98-2188794300 fariba dehnavi social security organization, tehran, ir iran