The Differences Between a Transition & a Polarized Lens

Modern technology allows for many different types of sunglasses. Two popular choices are transition and polarized lenses. Each offers a different set of advantages and possesses its relevant usages. However, the two are fundamentally different and are not interchangeable. In fact, transition and polarized lenses have many differences that one should know before purchasing one or the other.

Transition Lenses

• A transition lens, also known as a photochromic lens, is a special type of lens that darkens when exposed to the sun's ultraviolet (UV) rays. When the UV rays are removed, the lens turns back to its original clear state. However, the change is not immediate; sometimes it can take up to two minutes to darken or brighten. Transition lenses were first developed as glass lenses, but modern transition lenses can be made of polycarbonate or other plastics.

Uses of Transition Lenses

• Because of their unique properties, transition lenses are popular for regular eyeglasses. The darkening effect of transition lenses removes the need for a separate pair of sunglasses. Transition lenses can be used both indoor and outdoor, and they block UV rays just as well as sunglasses. This reduces the sun's harm to the eyes and is especially useful for children who spend lots of time outdoors. Some sunglasses are also photochromic, changing from dark to an even darker state.

Polarized Lenses

• Polarized lenses do not change depending on UV rays. Instead they only allow certain types of light to go through. Light waves are intrinsically polarized in a direction, and oscillate in a plane perpendicular to the direction of motion. Normal light possesses many different waves polarized in many different directions. A polarized lens is built so that only light polarized in one direction can travel through, effectively blocking a high percentage of light from penetrating.

Uses of Polarized Lenses

• Polarized lenses are used exclusively for sunglasses. Their main function is not to prevent UV rays from doing harm, but to prevent glare and make the eyes more comfortable. Light reflected from horizontal surfaces is generally horizontally polarized, a fact that polarized lenses take advantage of. As a result, polarized lenses are popular among outdoor enthusiasts such as skiers, boaters and bikers. They are also useful for driving and can be worn indoors by light-sensitive people.