The anterior surface of the eye is innervated by different functional types of sensory receptors. They include low and high threshold mechanoreceptors, thermal cold receptors and polymodal nociceptors. When the various subclasses of corneal and conjunctival receptors are stimulated selectively, sensations of different qualities are evoked usually containing a component of irritation. During inflammation or following accidental or surgical injury of the front of the eye, for instance after cataract or photorefractive surgery, nerves are often damaged at different points of their trajectory. Electrophysiological recordings of single nerve endings and axons from different models of corneal lesions (PRK, keratectomy) in experimental animals, show that corneal nerve fibers innervating the injured cornea change their firing characteristics and responsiveness to natural stimuli. Disturbances include presence of enhanced spontaneous activity, abnormal firing in response to the stimulus and postdischarge, depending on the functional type of sensory fiber affected, on the type of the lesion and on the time after injury. The altered firing pattern of the different functional classes of nerve fibers following injury may explain the change in threshold sensitivity and the abnormal sensations experienced by patients following anterior segment surgery. Different drugs used to reduce neuropathic pain (sodium channel blockers, antidepressive, antiepileptic) appear to be effective in attenuating hyperactivity and abnormal responsiveness of injured corneal nerve fibers and may be useful to prevent disesthesias caused by ocular surgery. Supported by SAF2005-07277 and BFU2005-08741 of the Ministerio de Educación y Ciencia and the Fundación Marcelino Botín, Spain.