[Physiopathology of eye burns]

Eye burns are frequent among eye traumas. They induce different effects on the ocular structures, depending on the type of burn: chemical, with an important difference between acids and bases, thermal, or ionizing rays. The physiopathology of eye burns reflects the different stages of progression, with a first stage of destruction, a second stage of cleaning and inflammation, and a last stage of reconstruction and scarring. The final prognosis depends on the initial lesions, not only involving the eye ball, but also the conjunctiva and eyelids. Chemical burns by basic fluids have the worst prognosis because they are able to penetrate the tissues quickly. Burns by acids have a better prognosis and thermal burns are located only at the injured area. Treatment is most effective at the initial stage of destruction and can dramatically change the prognosis. The secondary phase of cleaning includes the entire biochemical cascade of inflammation and the production of proteases. At this stage, treatment can be effective but must be closely monitored because it can inhibit progression to the last stage of scarring. At the scarring stage, neovascularization begins, induced by initial ischemia, the reconstruction of epithelium with a probable role of stem cells, the reconstruction of nerve fibers depending on the nerve growth factor (NGF), and the reconstruction of extracellular matrix in which matrix metalloproteinases (MMPs) are essential. At this stage, therapy can only be surgery of functional after effects and esthetic anomalies.