Sleeping without turning off the lights causes a variety of adverse effects on the body, such as affecting the quality of sleep, impairing vision and affecting physical development. Sleeping with the lights on for a long time, the light on the eyes constantly stimulate, will make the pupil can not be fully relaxed, the eye muscles have been in a state of tension, prone to myopia or retinal damage. Sleeping with the lights on for a long time will affect the secretion of melatonin, melatonin secretion will reduce the quality of sleep, resulting in nighttime dreams and easy to wake up, poor sleep quality. Teenagers sleep with the light on for a long time, one will affect the quality of sleep; the second will affect the secretion of growth hormone, resulting in growth retardation, affecting physical development. Therefore, unless medical or nursing care is needed to monitor the situation, lights should be turned off when sleeping to create a quiet and comfortable environment for sleep.