Reactolite Glasses And Windscreens

[Prudie]

My OH got Reactolite prescription glasses which he uses just for driving and keeps permanently in the car. It became obvious that they never tinted down even in direct sunlight so he took them back to the opticians who proved that they did indeed change colour. He left none the wiser and continued driving with them never changing. He's now discovered that if you hold them out the window into the sun they go dark. To me that suggests there is some filter in the windscreen glass that stops them reacting. Is this rubbish or does it happen to anyone else?

[hc4361]

That is correct and it is a safety requirement. It is dangerous to drive into a dark tunnel with dark glasses.

[retroactive]

Yes it happens to me. My prescrition lenses do not darken when I'm in the car. The Optician told me this.

[hc4361]

Mine don't darken in the car but they do in the greenhouse

[THECORBYLOON]

As far as I am aware, normal glass blocks UV rays and it is the UV that darkens the glasses. I'll do a quick search in a month.

[SlackAlice]

The windscreen being glass is filtering out UV light, which is what reactolite lenses need to go dark. Quite a common effect.

[dannyk13]

Explanation here:-
http://blog.myeyewear2go.com/why-dont-transition-lenses-work-well-in-the-car/

[THECORBYLOON]

I was aware that you can't get a tan through glass and it seems it blocks UVB (the rays that tan or Burn) but it allows UVA (the rays that Age the skin) so that may be why Reactolites go dark in a greenhouse as some UV rays get through. Windscreens are treated to block all UV but I was reading you can get lenses that do darken if driving.

[Prudie]

Well thank you for all your answers, I'm amazed quite frankly as the optician knew they were just for driving and he paid extra for the tinted effect.

[Spoffy]

I think it's great that the article linked by Danny refers to 'ultraviolent' light and the explanation of the phenomenon is provided by a 'Rob Vandal'...

[woofgang]

That’s a duff optician. I too wear glasses only to drive and every single optician I have ever been to has pointed out to me that the photoreactive lenses are not guaranteed to work in a car. Its a nuisance because my only option is to wear dark tinted prescription sunglasses. My “clear” lenses are photoreactive so I have got glasses if I need them.
hc its not a safety requirement. May be for HGV but for a private car driver (or motorcyclist) dark tinted sunglasses are quite legal. Just as well because my eyes stream in sunlight. It is fun driving into multi storey car parks as I have to swiftly switch my glasses as I get the parking ticket. happily there are no tunnels round here.

[hc4361]

woofgang, a person who doesn't need glasses to see can quickly and safely put their very dark sunglasses on top of their head or take them off entirely when they are driving.
If I took my glasses off I wouldn't be able see the end of my bonnet. I find those naff click on, flip up dark lenses to be just the job when driving - shade when I need it, quickly flipped up when I don't and my glasses on at all times.

[woofgang]

That’s your choice but its still not a requirement......

[riptide]

I was told by my optician that my reactolite glasses would not work in the car and if I drove a lot, then best to get prescription sunglasses for the car.

[Playbill]

I found my Reactolite glasses worked reasonably well in the UK - especially on bright, cold days - but barely at all in hotter climates. My optician told me that the change was triggered by UV light and a chemical reaction; and the chemical reaction worked faster and better when the glasses were colder. Seemed bizarre, but I proved this was true in South Africa earlier this year when I put the glasses in a fridge for five minutes before going outside in 30+C sunshine and they went dark very quickly. I bought a pair of clip on, flip up over glasses that solves the problem and makes driving into tunnels and similar instant light change scenarios much easier and safer.