The best you can do is go into Photoshop CS5 Preferences > Interface > and set the UI text size to Large.
If this is not enough, buy a Photography Program subscription. With Photoshop CC 2014, you can enlarge the UI 200% for Windows.
It's done by changing font size in your OS, not in Photoshop. What OS are you running?
That's incorrect. Changing the UI Font Size in Windows has no effect on Photoshop's UI font Size. That's why PS has its own UI settings.
I checked that and found that increasing Windows 7 UI font size did not change Photoshop's UI font size.
MacOS does not allow OS UI font changes. http://forums.macrumors.com/showthread.php?t=352057
That is a problem then. I can adjust my text sizes in the palette titles, menus, title bars etc. in windows and it has had the desired effect in CS and CC. There is a problem with the text size in CC 2014 however that many are experiencing including myself. I still use CC most of the time because of the bug. Although I'm running 8.1, adjusting the text size in 8.0 and 7 worked just the same with renditions of Photoshop prior to 2014.