a method and device to stabilize the cornea with fewer adverse effects . in particular , a greater stability and shorter treatment time are to be made possible . to this end , the cornea is locally irradiated successively at different sites so that collagen fibers are indirectly or directly crosslinked at the irradiated sites . in this way , the collagen fibers are advantageously crosslinked in a spatially resolved manner . accordingly , the entire eye need not be irradiated with tissue - damaging uv light , and regions having a weaker structure can be locally stabilized selectively . the sites of the cornea are preferably irradiated so that the collagen fibers are ionized in each instance by photoabsorption of a plurality of photons which each have an energy below an ionizing energy of a given molecule . after a short treatment period , strong covalent bonds are formed directly between the collagen fibers . crosslinking agents need not be used .