Protective role of corneal epithelium against ultraviolet radiation damage.

PURPOSE It is known that the corneal epithelium strongly absorbs ultraviolet radiation (UVR). The aim of the present study was to examine the protective role of corneal epithelium against UVR damage by comparing the biological effect of UVR exposure on whole corneas with that on de-epithelialized corneas. METHODS Six New Zealand albino rabbit corneas were exposed to UVR centred around 280 nm at a dose that causes biomicroscopically significant keratitis (012 J/cm(2)). Three corneas underwent manual de-epithelialization prior to UVR exposure. A control group of three rabbits underwent only manual de-epithelialization. The animals were killed 76 hours after treatment. The corneas were stained with haematoxylin and evaluated by light microscopy. RESULTS Corneas that underwent only the exposure to UVR showed a loss of epithelial cells in the treated area. No damage to keratocytes or the stroma was detected. Corneas that underwent manual de-epithelialization showed a loss of epithelial cells, and also keratocytes in the anterior quarter of the corneal stroma. However, corneas that were exposed to UVR after manual de-epithelialization showed very deep stromal damage. The keratocytes disappeared through the entire thickness of the stroma in the UVR-exposed area. CONCLUSION Exposure to UVR at 280 nm alone does not result in any deep damage to the corneal stroma and keratocytes. Manual de-epithelialization causes the disappearance of anterior keratocytes. However, the stromal damage caused by UVR in the de-epithelialized corneas was very deep. The corneal epithelium serves to protect the deeper corneal structures against UVR damage, probably by absorbing a substantial amount of the UVR energy applied to the eye.

[1]  Zsolt Bor,et al.  UV absorbance of the human cornea in the 240- to 400-nm range. , 2002, Investigative ophthalmology & visual science.

[2]  R. Cenedella,et al.  Quantitation of Ultraviolet Light-Absorbing Fractions of the Cornea , 1995, Cornea.

[3]  D. G. Pitts.  A COMPARATIVE STUDY OF THE EFFECTS OF ULTRAVIOLET RADIATION ON THE EYE* , 1970, American journal of optometry and archives of American Academy of Optometry.

[4]  P. Fagerholm,et al.  The Expression of Fas Ligand Protein in Ultraviolet-Exposed Rabbit Corneas , 2002, Cornea.

[5]  S. G. Sherashov.  [Spectral sensitivity of the cornea to ultraviolet radiation]. , 1970, Biofizika.

[6]  G. Klintworth.  The cornea--structure and macromolecules in health and disease. A review. , 1977, The American journal of pathology.

[7]  J. McLaren,et al.  Ascorbic acid content of human corneal epithelium. , 2000, Investigative ophthalmology & visual science.

[8]  V E KINSEY,et al.  Spectral transmission of the eye to ultraviolet radiations. , 1948, Archives of ophthalmology.

[9]  J. Friedenwald,et al.  Effects of ultraviolet irradiation on the corneal epithelium; exposure to monochromatic radiation. , 1948, Journal of cellular and comparative physiology.

[10]  S. Wilson,et al.  Epithelial injury induces keratocyte apoptosis: hypothesized role for the interleukin-1 system in the modulation of corneal tissue organization and wound healing. , 1996, Experimental eye research.

[11]  P. Fagerholm,et al.  Cellular response and reactive hyaluronan production in UV-exposed rabbit corneas. , 1998, Cornea.

[12]  P. Fagerholm,et al.  Apoptosis in UV-exposed Rabbit Corneas , 2000, Cornea.

[13]  E. Widmark.  Ueber den Einfluss des Lichtes auf die vorderen Medien des Auges1 , 1889 .

[14]  A. Ringvold.  In vitro evidence for UV-protection of the eye by the corneal epithelium mediated by the cytoplasmic protein, RNA, and ascorbate. , 2009, Acta ophthalmologica Scandinavica.

[15]  D J Moran,et al.  Pterygium and ultraviolet radiation: a positive correlation. , 1984 .

[16]  D G Pitts,et al.  Ocular effects of ultraviolet radiation from 295 to 365 nm. , 1977, Investigative ophthalmology & visual science.

[17]  A. Ringvold.  Corneal epithelium and UV-protection of the eye. , 1998, Acta ophthalmologica Scandinavica.