Eye drops for glaucoma contain medicine to reduce the pressure inside your eyes. There are several different types and we don't know for certain which works best. You may need to try more than one type of eye drop before you find one that works.
You may need to use two or more types of eye drop to control the pressure inside your eyes. You get eye drops on prescription from an eye specialist (an ophthalmologist). Here are some of the eye drops he or she is likely to prescribe (and their common brand names):
Most people start with eye drops called beta-blockers (such as betaxolol, carteolol, or timolol) or prostaglandin analogues (such as latanoprost and travoprost). Some eye drops combine two types of drug, usually timolol plus another drug. Examples include Ganfort (bimatoprost with timolol), Xalacom (latanoprost with timolol), and Cosopt (dorzolamide with timolol).
A summary of five studies (called a meta-analysis) showed that if the pressure in your eye is raised, eye drops can help preserve your eyesight and stop you getting glaucoma.  The summary found that, in a period of 5 to 10 years, eyesight became worse in:
But in one study eye drops didn't help in this way. 
A more recent summary looked at 10 studies. It showed that people with glaucoma or raised eye pressure who'd had treatment with eye drops had about half the chance of getting problems with their eyesight, compared to people who didn't have treatment. 
Eye drops can also help preserve your eyesight if you have glaucoma.  They seem to work best when combined with laser treatment. 
You'll probably benefit from using eye drops even if the pressure inside your eye is normal.  
When you put the drops in, some of the medicine gets into your bloodstream and can cause side effects. Closing your eye or pressing lightly on your tear duct for at least a minute after you put the drops in should help.
If you have a lung disease such as asthma, chronic bronchitis, or emphysema, some eye drops can make your symptoms worse. You shouldn't use betaxolol, carteolol, levobunolol, metipranolol, or timolol if you have any of these conditions. 
If you're using dorzolamide you may get a burning or stinging feeling in your eyes.  If you're using latanoprost eye drops, you might notice your eye colour getting darker. 
Side effects sometimes make it hard to stick with your treatment. But it's important to keep up with it. If you have problems with the treatment you're using, talk to your eye specialist (ophthalmologist), who may be able suggest a different treatment.