->  DW> reasons why I now wear graduated-focal glasses. 
 
-> Me, too.  When they reformulate them for the new eye-lens,  I will  
-> again see how well the current phototropic materials have advanced  
-> and perhaps include them...  I ain't convinced that sun exposure  
-> didn't contribute somehow to the cataract growth. 
 
-> :-)) 
  
UV is thought to have a role in initiating cataracts. I'm not sure 
whether it alters the rate at which they grow after being initiated. 
  
I have a pair of phototropic glasses, quite some time ago. I wasn't 
very happy with them. (Is "phototropic" the right word? I assume you 
mean materials that darken in strong light, and vice versa.) I found 
they were very temperature-dependent. The process of fading from dark 
back to transparent happened much faster when they were warm than cold, 
so *very* strong light was needed to keep them dark in hot conditions, 
but they became dark in dim light when they were very cold. Maybe 
they've improved. 
  
At present, I use a pair of magnetic clip-on dark glasses, which have 
polarizing lenses. Under most conditions, they work very well. There 
are problems, though, when I try to look at Liquid Crystal Displays, 
which also use polarized light. I have to take them off to gas up my 
car, since the display on the pump is a LCD one. Through the glasses, 
it just looks black. I would have expected the designers of the 
displays to think of this, and rotate the plane of polarization 90 
degrees. 
  
                           dow 
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