Hamba, Niguse (2014) A Systematic Review of the Histopathological Effects of Ultraviolet Radiation Exposure on the Ocular Structures in Human and Animal Studies. Masters thesis, Addis Ababa University.
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PDF (A Systematic Review of the Histopathological Effects of Ultraviolet Radiation Exposure on the Ocular Structures in Human and Animal Studies)
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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.
| Item Type: | Thesis (Masters) |
|---|---|
| Subjects: | Q Science > QM Human anatomy |
| Divisions: | Africana |
| Depositing User: | Emmanuel Ndorimana |
| Date Deposited: | 27 Nov 2018 12:25 |
| Last Modified: | 27 Nov 2018 12:25 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/7772 |
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