29 August 2006

Photochromic Spectacles

A few weeks ago, I noticed that even with my spectacles on, my right eye vision could not close in on distant objects. A visit to the optician has, fortunately, indicated that my right eye has decide to make a 25% leap from 200 degrees to 250 degrees instead of my worst fear that my eyeball is mutating into a button mushroom.

As I was browsing through the different spectacle frames, the friendly optician suggested to me on considering photochromic lenses, also known as Transition lenses due to the intense advertisement by the company of the same name. It costs about two times the price of a pair of normal lenses, which is the primary reason for the prolonged battle between the stingy and the inquisitive parts of me. Eventually, the latter won, so I ordered a pair.

Quite frankly, the tint of the lenses is pretty unnoticeable by the wearer. In fact, it is quite hard to visually discern if it is the lenses or the sky that has darkened, unless I take my spectacles off and look at the lenses, or compare the spectacles view with the non-spectacles view.

In addition, the degree to which the lens darken is pretty minimal. This is a consequence, I believe, of Singapore's hot weather, since, in short, photochromism is less effective in warmer surroundings due to the fact that the "deactivation" of the tint is a process fuelled by heat (ultraviolet, on the other hand, activates the tint).

But looking at it from another angle, my spectacles is my new portable UV detector. If my vision turns blacker while indoors (such as in a lab), I should perhaps take caution. Maybe one day I should even use it to test out Wien's displacement law on blackbody radiation.

Yay! I can finally see my favourite colour!

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