Cognitive Failure
Unfortunately for sight impaired users each version of Windows gets less friendly to assistive software. Back on NT/Win2K/XP screen readers could hook in to every application at a low level, and find out what it was writing to the screen, allowing a full picture of text and graphics to be built up, and to improve navigation for keyboard only users. Unfortunately each step in improving security in the later OS's, has had the effective of preventing the screen reader gathering the information, and aiding in navigation. There are assitive APIs in the OS, but they fall far short of what is required to give the best experience.
With a good screen reader an experienced user can drive applications as complex as Office and Visual Studio with no difficulties - with the monitor switched off! If it wasn't for the clicking of the braille display and slight sound from the speech synthsiser through the headphones, you wouldn't know the person on the other side of the partition was visually impaired.
Actually you would, from the sheer speed which they can pull up information, being unhindered by the visual ambiguity of most applications, particular the new flat colourless Windows 10 apps, and employing far better honed memory skills to be able to go straight to the right place without having to look for it!