On Fri, 20 Jul 2007 21:59:05 GMT, "George"
wrote:

are they any good for magnifying at a distance?

http://www.quicktest.co.uk are a good source for all sorts of
magnifiers. 20 quid gets you a jeweller's head-mounted magnifier, but
if you want the long focus distance type that you need for dentistry,
expect to pay around 150 quid. These are also (IMHO) too heavy to mount
on spectacles (without ripping your ears off) and need a full headband.