Welcome to question of the day #321

Eyetool question of the day#321

Is it possible to get photochromic lenses that go darker in a car?

Yes. Earlier generations of photochromic lenses went darker when UV light was incident on the lens. The UV caused a reaction in the chemicals in the lens material which made the lens go darker. They worked best in sunny, cool environments. This chemical reaction did not take place in a car because the car windows absorb UV. Not enough UV was getting through to cause the lens to be darker.

In my experience, this frustrated some patients and put them off purchasing photochromics.

Recent developments in photochromic technology have resulted in a photochromic lens in which the chemical reaction which causes the darkening takes place in sunlight even without UV.

 The only brand I know of that does this is Transitions XTRActive lenses.

Transitions technology blocks 100% UVA and UVB light rays and selectively filters blue-violet light indoors from modern light sources, and outdoors from the sun. Blue-violet light has been associated with the formation of cataracts and age-related macular degeneration.

They also help reduce glare caused by low winter sun, especially for people with some cataracts.

Even when inside away from sunlight the lenses come with a subtle hint of a tint so the eyes are protected from harsh lighting, perfect for the person who suffers from light sensitivity, or is just looking for a more comfortable pair of lenses.

They are available in brown, graphite green, and grey.

My patients like them.