How much sunlight is needed for the body to get the necessary signal to regulate hormones and neurotransmitters? This 99% statistic assumes people walk out of their house with sunglasses on and don’t take them off until it’s dark. Realistically people get direct sunlight exposure in the eyes in the morning and afternoon, but choose to use sunglasses during the middle of the day to prevent negative side effects such as pterygium. By all means if you see people wearing sunglasses during sunrise and sundown educate them. But I think you’ll find that is rare.