Abstract
Purpose::
The light absorption properties of the normal cornea are ensured by tissue components and fluids with the key role of antioxidants. Of corneal layers the epithelium and the anterior portion of the corneal stroma are most important. The purpose of this study was to examine the differences between light absorption properties of the normal cornea and cornea irradiated with UVA or UVB rays.
Methods::
Adult New Zealand white rabbits were employed. In the first group of rabbits the corneas were irradiated with UVB rays (312 nm), in the second group with UVA rays (365 nm). In both groups of animals the irradiation took place once a day during 5 days, a dose per day 1.01 J/cm2. The third group of corneas was irradiated with UVA rays (365 nm), once a day during 5 days, a dose per day 2.02 J/cm2). Absorbances of corneal centers (a circle of 6 mm diameter) of normal corneas (as controls) and irradiated corneas were measured over a range of 190-650 nm using a scanning spectrophotometer (HELIOSb 84021).
Results::
Comparing the effect of the same doses of UVA or UVB rays with the normal cornea, UVA rays do not significantly change corneal hydration and transparency and do not change the corneal light absorption properties. Similar results were obtained with two times higher dose of UVA rays. In contrast, repeated irradiation of the cornea with UVB rays evoke the increase in corneal hydration, changes of corneal transparency and the increase in corneal light absorption properties throughout the whole measurable UV-VIS spectral range than the normal cornea.
Conclusions::
UVA rays do not significantly change corneal light absorption properties, whereas UVB rays cause the profound changes in corneal light absorption properties.
Keywords: radiation damage: light/UV • cornea: basic science • keratitis