Glass remained a luxury material, and the disasters that overtook Late Bronze Age civilizations seem to have brought glass-making to a halt. Indigenous development of glass technology in South Asia may have begun in 1730 BCE.  In ancient China, though, glassmaking seems to have a late start, compared to ceramics and metal work. The term glass developed in the late Roman Empire . It was in the Roman glassmaking center at Trier , now in modern Germany, that the late-Latin term glesum originated, probably from a Germanic word for a transparent , lustrous substance.  Glass objects have been recovered across the Roman Empire  in domestic, funerary ,  and industrial contexts.  Examples of Roman glass have been found outside of the former Roman Empire in China ,  the Baltics , the Middle East and India . 
Testing for Radioactivity in Lenses
You can easily test a suspect lens using a sheet of high speed polaroid film (see posts below). Place
the lens glass element facing downward onto the polaroid sheet for a few days, and then develop. If
you see a foggy shadow or outline, you have a radioactive lens. You can also use longer exposure
times with a sheet of photographic paper from your darkroom, provided you extend the exposures
to several days and protect the paper from direct light fogging.