Trimble is aware of SketchUp’s issues on high-dpi displays (which have of late started cropping up on Windows too) but as of SU 2015 there is no fix. By policy they will not comment on possible changes in future updates, so for the near term your only solutions are to work at “best for retina” scaled resolution or live with the eyestrain. This will affect the menus, toolbars, etc. but not the drawing view.