A dog's sudden inability to open one eye may be caused by foreign bodies, trichiasis, conjunctivitis, keratitis, tumors, trauma, etc. First, check whether there are foreign bodies in the dog's eyes. If there are foreign bodies, you can Rinse the dog's eyes with normal saline, and then instill anti-inflammatory eye drops; if there are no foreign bodies, it is best to take the dog to the pet hospital to check the cause of the disease, and then carry out targeted treatment after confirming the cause. Do not blindly use medication.