When you change a glaucoma medication because of side effects, how long after you start the new medication should you have the eye pressure checked.

2 weeks. It takes 2 weeks for the old medicine to be completely out of the system and for the new medication to stabelize the pressure.
Two weeks. The standard procedure when starting a new medication for pressure lowering is to do a quick check two weeks after starting the new medication. This is enough time for the side effects of the previous one to have resolved and enough time for the new one to work. This is also a good time to ask questions if you have any.