A Systematic Review of the Histopathological Effects of Ultraviolet Radiation Exposure on the Ocular Structures in Human and Animal Studies
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Date
2014-07
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Addis Abeba University
Abstract
The transparent anterior segment of the human eye (cornea and lens), as well
as neural retina are greatly affected by dose dependent UV radiation
exposure.
The histopathological changes increased along with irradiation intensity and
UV-B exposure.
The most severe corneal lesions were observed following eye exposure to
some large doses of 0.72 J/cm2 to 1.2 J/cm2. The injuries caused by UV
irradiation to cornea are named photokeratitis also known as ultraviolet
keratitis. Photokeratitis is characterized by exfoliation of the corneal
epithelium, diminished visual perception, inflammation, edema, eye redness,
and burning-like pain from the ocular surface. Moreover, UV irradiation can
also go deeper through the corneal epithelial layer and provoke inflammatory
responses that involve the full corneal thickness
The radiation that hits the lens is first filtered by the lens capsule and at 300nm
(range from 290 to 315 nm) wavelength, approximately 60% of the radiation is
transmitted by the anterior capsule. The transmitted radiation induces
apoptosis in the lens epithelial cells and thereafter the cortical fibers which
contribute to the formation of lens cortical opacities. Because lens epithelial
cells are responsible for maintaining much of the homeostasis of the
underlying fibers, damage to lens epithelial cells may also result in
abnormalities in lens fibers. For proteins, longevity is commonly assumed to
be correlated with long-term retention of native structure.
The irradiations ranging from 380-520 nm contribute to degenerate outer
nuclear layer area of the retina. Shorter wavelength light also is the most
hazardous it is known to generate reactive oxygen species (ROS) in the
retina. The retinal pigment epithelium is especially susceptible to oxidative
stress because of its high light, oxygen tension, fluorophore and
membrane lipid levels.
Acute and chronic exposure of the eyelid to UV radiation causes common
types of skin lesions around the eyelids that frequently result in basal cell
carcinoma, squamous cell carcinoma, sebaceous cell carcinoma, and
malignant melanoma
In conjunctiva UVB at the dose of 0.72 J/cm2 per day showed conjunctival
epithelium metaplasia and loss of goblet cells thereby decreasing of tear
quantity
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Keywords
Human; Animal