With the coming of brighter days, it is an ideal time to start thinking about shopping online for some cheap prescription glasses with a sunglass tint or maybe even try some transitions or photochromic lenses. This can cause some confusion even with all the information available online when shopping for glasses, so we thought we would take a little while to explain some of the background for these “magical” lenses.

A smart Alec once went into an Optician’s shop and asked for information about phototropic lensesfor his spectacles, you know, the ones that change colour with the light.  Aha!  thought the Optician, he means photochromic (or photochromatic glasses to some), that being the generic term which we all understand.  However, better check with the handbook of optical terminology; Oh dear, the smart Alec is right,  the correct generic term for these lenses is actually, phototropic.  Now if there is one thing we all hate more than a smart Alec, it is a smart Alec who proves us all wrong.  However let us stick to the word we all know and like and  *! *%”***  to the smart Alec.

 

The first successful photochromic glass was the Reactolite by Chance Pilkington of St.Asaph in North Wales, a modest establishment which supplied the whole world with glass “drop blanks”.  Actually, that may not be entirely true; there may have been one or two remote corners of the world which had a preference for the inferior products of an alternative supplier, but the modern spectacle wearer was certainly warming to this new glasses technology.

 

Reactolite lenses were quite a revolutionary concept and soon became extremely popular with the spectacle wearing public and also as ordinary non prescription sunglasses.

 

The second generation Reactolite lenses came in three grades, light to not so light, medium to not so medium,  and mediumish to dark.  They were available only in brown colours which is the first choice colour in Europe but not in the USA, where the spectacle and sunglass wearers have a preference for grey.

 

With the third generation of  Reactolite lenses,  Pilkingtons really “hit the jackpot”. The Reactolite Rapide lenses (grey in colour) immediatlely became and remained for some considerable time, the world leader and first choice for all who had a preference for photochromic lenses. The big advantage of the Rapide was that it changed colour much faster than previous products.

 

In the meantime, experiments were continuing to produce a plastic photochromic material to satisfy the latent demand for such a lens in the increasingly popular range of plastic lenses.

 

The first commercially successful plastic photochromic lens was the Transitions,  now, like Reactolite before it, a household word.  Initially, opinions were divided as to whether the Transitions were as good or better than the Reactolite.

 

 We are now enjoying the fourth generation of Transitions lenses and it is difficult to imagine that there will be any further improvements.  However, if a lens material could be produced which changes from totally clear to totally dark instantaneously and back again in a similar bat of the eyelids, then it is difficult to believe that further demands will be made of the researchers in the lens industry.

 

If in fact such an instantaneously changeable material is ever developed, then nowhere will it be more welcomed than on Merseyside, where opticians, for the last forty or so years, have had the unenviable task of explaining to their customers that these Reactolite/Transitions do not lighten immediately one drives into the Mersey Tunnel, nor do they darken immediately one drives out.  Indeed you would need to have your head out of the window for them to noticeably change at all, as the windscreen itself absorbs most of the UV necessary to activate the colour change. If you were to try this method, they may just about be beginning to lighten by the time the wearer requires them to darken again!

 

Alas, the unknown penalties of living in the beautiful city of Liverpool (and of course the almost equally beautiful surrounding areas of Merseyside)

Tags: Buying Glasses Online, Photochromic, Transitions

This entry was posted on Wednesday, April 8th, 2009 at 9:31 pm and is filed under Lenses. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.