What are photochromic lenses? Photochromic lenses change the level of darkness depending on the intensity of sunlight. Indoors, they usually remain colorless and look like regular spectacle lenses. In bright light they darken. This allows them to protect the visual organs from intense solar radiation. Many people who constantly wear prescription glasses choose photochromic ophthalmic products, as they correct vision and reliably protect their eyes from the sun. Thanks to this, there is no need to buy two pairs of glasses: corrective and sunglasses, since models with photochromic lenses allow you to replace two pairs. As soon as a person enters a room from the street, they become colorless. The degree of darkening of photochromic lenses changes under direct exposure to ultraviolet rays. Ultraviolet light can pass through the cloud layer and negatively affect the visual organs. "Photochromes" remain dark even in cloudy weather. The main condition for changing color is direct rays. If a person is driving a car on a sunny day or in a room illuminated by clear rays, the lenses will remain light. This is due to the fact that ultraviolet radiation does not pass through window glass. There are models that respond to the intensity of the light flux, and not just to ultraviolet. They will darken the car or room, but the level of darkness will not be saturated. The color will change by no more than 50%.