Vasoconstrictive, alpha-sympathicomimetic eye drops are ophthalmic drugs that are extensively used. However, patients often complain of typical dry eye symptoms, especially after long-lasting application of such eye drops. In the present study, the effect of sympathicomimetic eye drops (0.026% oxymetazoline) on the tear volume and tear flow of 38 healthy individuals was determined quantitatively by means of objective fluorophotometry. Both tear volume and tear flow were found to be significantly (P less than 0.001) decreased up to 6 h after instillation, reaching a minimum 90 min after application (tear volume: -63%; tear flow: -71%). Thus, alpha-sympathicomimetic eye drops containing 0.026% oxymetazoline lead to a marked and protracted decrease in tear volume and tear flow. After frequent or long-lasting application, this fact may be responsible for severe dry eye conditions.