Have you ever wished you didn’t have to carry both prescription glasses and sunglasses with you? Photochromic lenses are the solution. These intelligent lenses automatically adapt to light conditions, darkening outdoors and becoming clear again indoors. At CristalesGafas, we explain exactly what they are and how they work.
What Are Photochromic Lenses?
Photochromic lenses — also called “transition lenses”, after one of the most well-known brands — are prescription or non-prescription lenses that automatically change their shade depending on the amount of ultraviolet (UV) light they are exposed to.
When you are indoors or in low UV-light conditions, the lenses remain completely clear and transparent, just like conventional prescription lenses. When you go outside and are exposed to sunlight, the lenses darken within minutes to protect your eyes from the sun and glare, functioning as proper sunglasses.
How Do Photochromic Lenses Work?
The magic of photochromic lenses lies in their chemistry. These lenses contain special molecules — usually based on silver halide or organic compounds — that react to UV radiation. When UV light hits these molecules, they change their molecular structure and absorb more visible light, causing the lens to darken. When the UV source disappears (when you go inside), the molecules return to their original structure and the lens becomes clear again.
This process can repeat itself thousands of times without losing effectiveness, making photochromic lenses very durable.
Darkening and Lightening Times
Modern photochromic lenses darken in about 30-60 seconds of sun exposure and return to their clear state in approximately 2-5 minutes after entering an indoor environment. The speed of this process can be affected by temperature — in very cold conditions the lenses may darken more intensely and take slightly longer to become clear again.
Types of Photochromic Lenses
- Standard photochromic lenses: Work well outdoors but may not activate inside vehicles, as car windscreens filter out much of the UV light that triggers the darkening reaction.
- Extra-active or driving photochromic lenses: Specifically developed to also react to visible light, so they activate inside vehicles where UV light is blocked by the windscreen.
Photochromic Lenses at CristalesGafas
At CristalesGafas, we offer photochromic lenses for single vision, progressive, and bifocal prescriptions. Our photochromic lenses are manufactured in Europe and provide complete UV400 protection. Say goodbye to carrying two pairs of glasses — discover the convenience of photochromic lenses today.