U L T R A V I O L E T
R A D I A T I O N ( U V R )
The cornea absorbs wavelengths below 300 nm, the
lens absorbs wavelengths between 300 and 400 nm,
and wavelengths greater than 400 nm are transmitted
to the retina. The lens absorbs almost all UVR to which
it is exposed, and any resulting unstable free radicals
cause molecular changes.73 The first active tissue of the
lens that encounters UVR is the lens epithelium, which
is susceptible to damage from free radicals. Morphologic
changes apparent in the epithelial layer may lead
to irreversible changes throughout the lens, although
the mechanism by which this progresses has not been
defined.74
UVR absorbed by lens fibers causes oxidative damage,
leading to degradation and modification of lens
proteins. An association exists between ocular exposure
and increased risk of lens opacity. UVR absorption
also increases chromophore concentration; yellow pigments
accumulate in the center of the lens. The yellowing
may progress to a dark-brown hue, which is
called lens brunescence.