Usually, the harm of watching cell phones at night without turning on the light may induce eye diseases, cause endocrine disorders and sympathetic nervous disorders. 1. induced eye diseases: the human body in the dark environment to watch the cell phone is easy to make the eyes overly fatigue, and cell phone glare may lead to the eyes of the photoreceptor material is overconsumed, and then trigger dry eye. Long-term this may also make the pupil due to prolonged dilation and lead to abnormal intraocular pressure, thereby causing damage to the optic nerve, inducing glaucoma, macular degeneration. 2. Causing endocrine disorders: the dark environment can make the human body secrete a lot of melatonin, if long-term night watching cell phone without turning on the light may inhibit the secretion of melatonin, resulting in endocrine disorders in the human body. 3. Sympathetic nervous disorder: the human body in the dark environment to look at the cell phone, usually need to be highly concentrated and attention, and cell phone light will stimulate the brain excitation, so it may lead to the human body nerves are in a high-pressure state, and then lead to sympathetic nervous disorder, palpitations, insomnia, dizziness and other symptoms. However, the harm caused by watching cell phones at night without turning on the light and symptoms may vary from person to person, so if there are uncomfortable symptoms, we recommend timely medical attention, and try not to watch cell phones at night with the light off in daily life, and should be controlled to watch the time of the cell phone.