Recall that sunlight is 42% infrared and this is nature’s version of photodynamic therapy. UV/IR combo light in sunlight is your vaccine to cancer. Amongst all the different types of cancer treatment, photodynamic therapy (PDT)- where light in is used to destroy malignant cells – might have one of the strangest side effects: patients are often better able to see in the dark. Why? with PDT red light is used to lyse cancer cells. The same red light stimulates the repair of the photoreceptors in the eye and affects how retinal acts with those photoreceptors.