Turn on accessibility options in the login window on Mac
You can turn on certain accessibility options in the login window to make it easier to log in to your Mac.
On your Mac, choose Apple menu
> System Settings, click Lock Screen 
in the sidebar, then click Accessibility Options on the right. (You may need to scroll down.)Turn on the accessibility options—such as VoiceOver or Zoom—you want to enable in the login window. You may need to enter an administrator name and password.
The options you turn on are enabled in the login window for all users of your Mac.
If you select the Accessibility Keyboard or Switch Control option, your current keyboard or switches settings are applied in the login window for all users (until another user turns the options off in their Accessibility Options settings).
Click Done.
Anyone who logs in to your Mac can temporarily turn the options on or off in the login window by pressing Option-Command-F5 (or if your Mac or Magic Keyboard has Touch ID, by quickly pressing Touch ID three times) to display the Accessibility Shortcuts panel.
If you use an option in the login window and would like to use it whenever you work on your Mac, you can turn on the option in Accessibility settings. On your Mac, choose Apple menu > System Settings, then click Accessibility in the sidebar. (You may need to scroll down.)