Transition lenses, also known as photochromic lenses, are a type of eyeglass lenses that automatically darken in response to UV light. These lenses are designed to provide a comfortable and convenient solution for people who need to wear prescription glasses and also require protection from bright sunlight.

Transition lenses are made of special materials that contain light-sensitive molecules. When exposed to UV light, these molecules undergo a chemical reaction that causes the lenses to darken. The amount of darkening depends on the intensity of the UV light, so the lenses will adjust to different lighting conditions.

When indoors or in low light conditions, transition lenses remain clear or nearly clear, allowing the wearer to see clearly. When the wearer goes outside into bright sunlight, the lenses darken to provide protection from harmful UV rays. This feature can be especially useful for people who spend a lot of time outdoors, as it eliminates the need to switch between prescription glasses and sunglasses.

Transition lenses come in a range of colors, from gray to brown to green, and can be made with different lens materials, such as polycarbonate or high-index plastic. They are available in both single-vision and progressive lenses and can be fitted to most types of eyeglass frames.

It’s worth noting that while transition lenses do provide UV protection, they are not a replacement for sunglasses with polarized lenses, which offer additional benefits such as glare reduction and improved contrast. Additionally, transition lenses may not darken inside a car, as car windshields block most UV light.