The association between symptoms of discomfort and signs in dry eye

There is an intuitive causal link between the signs of dry eye observed by clinicians and the severity of symptoms experienced by patients. However, this expectation is challenged by asymptomatic patients with obvious tear film anomalies and extensive ocular surface compromise and, conversely, by patients with intolerable symptoms of dryness in whom only minimal disease can be observed. Knowledge of how symptoms reflect the state of disease would enable clinicians to better understand and manage patients with apparently idiosyncratic disease presentations. This paper reviews the literature and describes the difficulties of investigating the correspondence between symptoms and signs in dry eye. The measurement of and analytical methods used to compare these two clinical areas are discussed. Theoretical aspects of the relationship between symptoms and signs are also covered. Typically, a positive relationship exists between the severity of symptoms and objective tests in dry eye, but, on balance, data suggest that the association between symptoms and the majority of these tests is not strong; thus, the power of predictive inference of one from knowledge of the other is low. Firm conclusions cannot be made on the nature of the relationship at this time because of limitations in our ability to measure either individually.