Eye drops are liquid drugs, which are less stable. After opening the cap, they are prone to physical and chemical changes due to exposure to air, resulting in weaker eye drops and even harmful substances due to the decomposition of drug ingredients, which can cause damage to the eyes. Therefore, the use cycle of eye drops will become shorter after opening, and it is generally recommended that they be used up within a specified period of time to avoid contamination of eye drops by exposure to air for too long. Different dosage forms of eye drops have different opening times. 1, single pack eye drops: single pack eye drops opened for 1 day, 24 hours later should be discarded and no longer applied. Because this single-stick eye drops do not contain preservatives, open easily lead to eye drops deterioration; 2, bottled eye drops: bottled eye drops usually contain preservatives, but even if containing preservatives, eye drops after opening the bottle preservation environment has changed, the effect will gradually weaken. Generally after 1 month of use should not be used. Even if it is not used up within 1 month, it may lead to bacterial contamination due to repeated opening and closing of eye drops, and the use of contaminated eye drops may lead to lesions of the cornea and conjunctiva. Eye drops should be stored in a cool, dry and ventilated place, avoiding sunlight, high temperatures and humid environments. The cap needs to be tightened during use to isolate the air and reduce the chance of contamination or outflow of the solution. Before use, see if the eye drops are clear and transparent, whether there is discoloration, and whether they have become cloudy or flocculent precipitates, if there are these phenomena, they should not be used again. It is also important to note that all eye drops should be used under the guidance of a doctor.