ULTRAVIOLET RADIATION AND THE EYE - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 261

Figure 5. The solid line shows the exposure limit, expressed as the reciprocal of the spectral response
curve S UV (O) compared to the photobiological action spectra (not normalized) for erythema, and
photokeratitis expressed as thresholds. The exposure limits for ultraviolet radiation were extended
into the UV-A region in 1985. Open triangles are the threshold data for photokeratitis. Solid squares
are the data for permanent cataract, and open squares are for reversible cataract.
The natural protection against overhead UVR afforded to the eye by the upper lid
and brow ridge may be of little value for exposure to open-arc sources in the work
place, since the source may frequently be within the normal horizontal line-of-sight.
Hence greater eye protection is routinely required in industrial applications. Goggles
and face shields are required when working around electric arc welding, which produces
high levels of all UVR wavelengths. Close fitting facemasks with low transmittance to
UVR, visible and infrared radiation are used for protection 1 .
18. Conclusions
The design of instrumentation intended to measure the photobiological dose to
ocular tissues must take into account a number of geometrical shading factors, such as
the eyelids and brow ridge, as well as behavioral aspects of vision. These geometrical
and imaging factors challenge the task of attempting to accurately measure the
photobiologically significant exposure of the cornea, lens and retina to ultraviolet,
visible and infrared radiation. The human eye is actually exposed to a very small