I can see the option to reduce the brightness of the screen on my laptop but not on my desktop. Is there a way to adjust this on my pc?
Install graphics driver
Settings > Additional drivers
Option to change brightness should be in settings:
Settings > Brightness & Lock
Do you use latest version of elementary OS?
Install Brightness Controller with the following commands:
sudo add-apt-repository ppa:apandada1/brightness-controller
sudo apt update
For Version 1 with up to 4 Monitor Support:
sudo apt-get install brightness-controller-simple
For Version 2 with Multi Monitor Support and other features:
sudo apt install brightness-controller
Note: This does not decrease the intensity of backlight, so won't save your batteries. But you can use this as a last resort to save your eyes.