toshiba brightness issue

I have toshiba laptot. function keys are not working and adjust brightness option is also not showing in the power section.
then how can I reduce the brightness of my laptop.
please help on this

To get the function keys working you can go to Desktop Assist (Toshiba) > Tools & Utilities > System Settings > Keyboard > Special function mode.
Even if it looks right do an Apply > OK that will probably start the service up again. Or you can reboot.

However you can simply use FN+F to access the functions anyway.

Other ways to the Brightness are Charms Menu > Settings > Brightness (Windows 8.1).
Or Control Panel > Display > Adjust Brightness.

You can go to Toshiba support and download the Function Key utility, and System Settings utility from them.

If it shows a brightness indicator while hitting the keys but it seems not to stay at the brightness you set, you could have "adaptive brightness" enabled in the power profile. This Tutorial should show how to disable it if it is on.