Photochromic lenses the good and bad.

You want sunglasses and regular glasses? Without changing pairs? We can do that, and yes, it’s a photochromic lens, it darkens when exposed to UV light and lightens back to clear when indoors. These lenses are used as sunglasses in bright light and regular glasses indoors, and are a great option for many patients, so here's the good and the bad.

The Good:

• Very convenient, you can use these glasses in most situations;

• They offer UV protection blocking UVA and UVB;

• You don’t have to worry about remembering your sunglasses; and

• Many colours and styles are available.

The Bad:

• They can take some time to get dark or light depending on the brand;

• They WILL take longer in cold weather and go darker; and

• They will NOT get very dark inside your vehicle because the windshield blocks UV light.

There are two types of technology that go into making a photochromic lens. One type uses molecules of silver chloride or silver halide embedded in the lens. These are transparent to visible light when under artificial lightening but darken under ultraviolet light. The second type uses organic photochromic molecules that when exposed to ultraviolet rays go through a chemical process that causes them to change shape and absorb a percentage of visible light aka, they darken! Both processes are reversible once removed from ultraviolet light causing them to return to their transparent state.