The later Anki 2.0 releases increase the size of the text and images to make them easier to see on high resolution displays, but it means that everything is a little less sharp. If you preferred the old behaviour where things were smaller but sharper, you can return to this old behaviour by following the steps on the following link:
http://ccm.net/faq/32589-windows-8-1-disable-display-scaling-on-hig...
Please note that Anki 2.0 is no longer supported - if you're not using a lot of old add-ons, a better option would be to upgrade to the latest Anki 2.1 release, which has better support for high resolution displays: https://apps.ankiweb.net/