How do photochromatic lenses change in response to light?

Photochromic lenses are designed to enhance visual comfort by adjusting their tint based on the amount of UV light exposure. In bright light conditions, particularly outdoors where UV rays are more prevalent, these lenses darken. This provides additional protection against glare and harmful UV radiation. Conversely, when the wearer transitions to a low-light environment or indoors where the UV light is minimal, the lenses become clear again, allowing for normal vision without the dark tint. This dynamic response is a defining feature of photochromic technology, making option A the most accurate description of how these lenses operate in varying light conditions.