Combigan is the eye drop preparation containing a couple of active ingredients called Bromonidine Tartrate and Timilol Maleate, both of which are medicines help reducing raised pressures with the eyes. Both the ingredients work in different styles producing the combined effect greater than either ingredients produces it. The consistent flow of fluids called aqueous humor through the eyeballs naturally maintains the pressure within the eyeballs. Aqueous humor is produced by a part of the called the ciliary body and it drains out of the eyeball through cannels known as the trabecular meshwork. As in glaucoma, if the aqueous humor outflow is blocked, the aqueous humor builds up inside the eyes, enhancing the pressure within the eyeballs. Such pressure is required to be decreased or else it could damage the optic nerve and damage vision as the result.

Bromonidine Tartrate is the kind of medicine called the alpha agonist which works by stimulating the alpha receptors found on the blood vessels that supply the ciliary body. This affects the blood vessels to constrict and decreases the amount of watery fluids that filters out of the blood vessels forming aqueous humor into the eyeballs which reduces the pressure within the eyes. Timilol Maleate, the other medicine is called beta-blocker which blocks beta receptors in different parts of the body. Blockage of beta receptors in the eyes decreases the amount of aqueous humor that is produced. Timilol Maleate consequently decreases the inflow of aqueous humor into the eyeballs and so reduces the pressure within the eyes. The combination of both of these medicines is used for lowering the pressure in the eyes when the beta blocker eye drops does not lower sufficient pressure itself.