Generally two eye drops need to be used at least 5 minutes apart. The excretion of eye drops mainly depends on the flushing of tears, 4 minutes after the drops, about 50% of the drug residue, so it is recommended that if you want to use two kinds of eye drops at the same time, at least 5 minutes interval after one kind of eye drops and then another kind of drops, if the other kind of drops too early, it may be the first time the eye drops flushed away, can not achieve the effect. It is not necessary to put too many drops at one time. The volume of the conjunctival sac is only 30 microliters (1 microliter = 0.001 milliliter), and if too many drops are put in at one time, it will be easy for them to flow out of the conjunctival sac, so it is enough to put in one or two drops at a time. It is recommended that patients use eye drops under the guidance of a doctor and not without authorization to avoid adverse consequences.