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Ultraviolet analysis on in vitro corneas following tissue removal

Exposure to ultraviolet (UV) radiation, even in small quantity, can cause several damages to the human eye. Continuous exposure the ultraviolet rays may cause corneal swelling, lens opacity (cataract), harms to the retina and pterygium. The purpose of this work is the study of the alteration of the corneal tissue and its UV natural protection in different scenarios, using a device previously developed, which provides measurements of corneal transmittance in the UV range. The device consists of ultraviolet source and detector, digital processing and visualization of results in real time. The dual beam system provides tissue UV transmission with accuracy of 0.25%. A protocol has been established for testing the UV protection on the cornea, as well as performing the removal of the corneal tissue, simulating refractive keratotomy. We have observed that it's evident that each corneal layer has influence in the UV absorbance, the results show the influence of the epithelial layer (~50μm depth), the little endothelium influence (~10μm depth), and the stroma layer is responsible for the strongest influence (~350μm depth). Preliminary studies on 42 human corneas lead to demonstrate that as the stromal layer is reduced, there is significant loss of the natural UV protection of the cornea, sometimes presenting a very restricted protection.