G'morning David and Paul, 

Coincidentally,  I'm due this day to get a new prescription to fit 
my new right lens following catatact surgery.  I, too, took the 
opportunity to enquire about the state of photochromatic 
materials,  and was told that materials have inproved considerably 
over the last few years - with plastic implementations 
outperforming glass. 

However, they were unwilling to comment on the interaction with 
other glassware, light sources and real benefits - so I left it 
well alone.

 -> Beyond that, what's most important in any sunglasses is their
 -> ability to absorb UV.  Sunglasses that don't do that just widen
 -> your pupils and let more UV in.  IMO it's safer to get a separate
 -> pair of sunglasses designed to do just that.

Or a good hat...  the sun specs that seem outright dangerous to me 
are the `Beatles' efforts - little dark spots that might protect 
the fovea, probably open the pupils and certainly allow incidental 
sunlight at the parafoveal and peripheral surfaces without 
hinderance...

 DW> Yes. But almost all common glass and plastic lenses, even if they look
 DW> very clear in visible light, are strong absorbers of UV.

Often overlooked entirely by lay persons and glass salespeople.

 DW> Contact lenses are also protective.

Heh, heh ... my right eye's lens now boasts 22.5 diopters and "UV 
protection with blue light filter", care of Alcon Labs in Fort 
Worth ... the ultimate contact lens ?

Not without some cost,  I hasten to add - the implacement led to 
an infection of the foveal area that provoked a temporary scotoma 
that was more intrusive than the cataract...

:-(
 



 
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