retinopathyofprematurity.org Macular Degeneration sidebar:
The spectra of fluorescent lamps
The graph of the spectrum from a typical "Cool-white Deluxe" fluorescent lamp shows the wavelengths in nanometers along the horizontal axis and the energy emission in Watts per ten nanometer-band as the vertical axis. The example shown is from Sylvania, but the spectra of the same lamp type from its other manufacturers are virtually identical.
The five rectangular bars that stick out above the smooth curve of the broadband spectrum average the mercury emission lines as columns ten nanometers wide because the graph would otherwise become to tall. They are really very narrow spikes, a great many times taller and thinner than on this graph, and they are virtually the same for most types of fluorescent tubes, such as "Daylight" or "Cool White Deluxe", etc.. The major difference between those types is in the shape of the broadband curve which can be shifted somewhat by using different phosphor mixtures to obtain different color temperatures, but the main emission lines are not much affected by these manipulations.
Compact fluorescent lamps (CFLs) exhibit greater variations in the
relative proportions of these spikes than the fluorescent tubes, but
most of the spectra I saw include the strong spike at 435.8
nanometer. You can find a collection of spectra from some of
the different CFL models at
(Scroll down to the sub-heading
The spectra shown there range from having the tallest mercury
emission line at 435.8 nanometers, as tall or even taller than in
the fluorescent tube spectra, in models such as “Dollar Store”
Sunbrite “warm white” 3000oK 18W and Trisonic “soft white” 6500oK
30W, to third tallest in such CFL models as Osram 2700oK 9W,
Children's eyes are still more transparent
to all blue and shorter wavelengths, including even some of the even
more energetic near-ultraviolet light which adults cannot see, by
definition. In their case, the retinal damage potential is
shown in the "Aphakic eye" columns in the above-linked Table of
damage-weighted retinal irradiances.
Children's eyes are still more transparent to all blue and shorter wavelengths, including even some of the even more energetic near-ultraviolet light which adults cannot see, by definition. In their case, the retinal damage potential is shown in the "Aphakic eye" columns in the above-linked Table of damage-weighted retinal irradiances.
Many fluorescent tubes emit only small amounts of energy in the
ultraviolet range below 400 nanometer, as in the above graph and
the Table below, but others have stronger emissions in that region
that are not fully filtered by their
glass wall or their plastic diffuser.
Many fluorescent tubes emit only small amounts of energy in the ultraviolet range below 400 nanometer, as in the above graph and the Table below, but others have stronger emissions in that region that are not fully filtered by their glass wall or their plastic diffuser.
Column 1 in this Table lists the wavelengths in nanometers (nm) in which the “Cool White Deluxe” lamp emits its radiation.
Column 2 shows the energy of that emission in Watts for each wavelength interval of ten nm. Please note the emission spike at 435 nm.
The third column gives the U.S. Occupational Safety Guidelines' action spectrum for the "blue-light hazard function" which the National Institute for Occupational Safety and Health (NIOSH) first published in 1980. It shows the maximum vulnerability range from 435 to 440 nm where the emission from the lamp is strongest [SLINEY DH, WOLBORSHT ML. Safety standards and measurement techniques for high intensity light sources. Vision Res 1980: 20: 1133-41 (see page 1137)] .
The fourth column multiplies the irradiance from the lamp in column 2 with the value of that “blue-light hazard function” in column 3 to obtain the "damage-weighted irradiance" from that wavelength band that reaches the retina in a normal adult eye. The lens of that eye is usually yellowed and so filters out much of the most damaging blue and violet radiation.
Column 5 lists the corresponding photic hazard function for aphakic eyes, that is, eyes like those of children whose lens is not yet yellowed and therefore lets through the even more damaging radiation at shorter and therefore more energetic wavelengths.
The last column lists the damage-weighted irradiance from those fluorescent nursery lamps on the retinae of unprotected eyes like those of children.
Continue to a discussion of damage-weighted irradiance and its effects on the retinae of premature babies when their still developing eyes are at their most vulnerable stage.