How quickly do fluorescent microscopy lenses detriorate?
It seems that the high powers of UV used in fluorescent microscopy makes objective lenses autofluorescent. The worst cause of degredation is probably leaving the shutter open (with lens transmitting UV) when the microscope is not in use: we considered using foot switches to hold the shutter open. With our objectives, 5 yr old ones give an exposure time of 3 min with only epifluorescence on and no specimen, and have a clear yellow glow with UV light, while new ones give no reading. I know one company doing human clinical diagnosis that returns their objectives every 11 months for replacement under guarantee – which apparently happens without question. We suspect the glue holding the lens together is at fault and not the glass.
