Dry eye is a complex multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface. Inestability of the tear film may also cause an increased osmolarity of the tear film, thus triggering epithelial osmotic lesions and inflammation. The occurrence of such changes on the eye surface results in disturbances of homeostatic neurophysiologic mechanisms which further worsen the process and vicious pathophysiological cycles occur.