Low energy lamps and eye lens autofluorescence

Tungsten filament lamps are rapidly being displaced from the market-place by compact fluorescent lamps. Although the colour temperature and total luminous output of a fluorescent lamp may be similar to that of an incandescent lamp, the output spectrum is very different. The peaks of the mercury vapour spectrum at 365.4 nm (UV) and at 435.8 nm (blue) are close to the peak fluorescence excitation wavelengths in the human lens, and it has been shown that such fluorescence can lower sensitivity to low contrast objects. This effect could also explain the reported preference for brown, red and yellow tinted lenses often reported by elderly patients, as these coincidentally block the ultraviolet and blue exciting wavelengths.