[Focusing on the functional dry eye]

Dry eye is one of the most common eye diseases characterized by disturbance of tear film homeostasis and a series of ocular discomforts. Discrepancy of ocular subjective symptoms and objective signs, especially unexplained severe symptoms without visible signs has been a long-time confusion for ophthalmologists. Functional disorder is a medical condition that impairs normal functioning of bodily processes due to autonomic nervous dysfunction caused by cerebral cortical dysfunction, but at the exterior, there is no appearance of abnormality. Clinical manifestations are the disease symptoms with a lack of exact physical signs and examination results to confirm the diagnosis. According to the definition and characteristics of functional disorder, we put forward the concept of functional dry eye. We assume that those patients with dry eye symptoms but without detectable signs could be classified into such a functional dry eye subtype. The possible mechanism, clinical manifestations, and treatment strategies are further discussed. (Chin J Ophthalmol, 2019, 55: 885-890).