I just upgraded to a 4k monitor, and supposedly Visual Studio should be able to handle a high dpi monitor just fine. But it's not working for me and I'm not sure why. I have this same problem in Visual Studio 2015 and 2017.
In the screenshot below (taken from a zoomed-in screenshot in Paint.Net so the individual pixel divisions are visible), I have overlapped the Visual Studio window with Chrome, and you can see that the ClearType text is rendered at lower resolution and then scaled with Visual Studio, resulting in a very ugly doubling of the colored pixels, whereas in Chrome, the text looks great.
This makes the code extremely hard to read/edit in Visual Studio, as the text all looks blurry. I have two monitors hooked up, one 4k with the desktop scaling set to 200% and a regular 1080p monitor with desktop scaling set at 100%. I've tried playing around with a few settings, such as cranking up the scaling on the 1080p monitor or changing which one was primary. None of these settings made any difference. Reboot also didn't help.
Since there aren't many levers when it comes this sort of thing I'm at a loss for where else I should be looking at to fix this. Any suggestions on how this could be fixed?