Influence of eye position on the Schirmer tear test

Abstract

The Schirmer test (ST) evaluates the volume of tears in potential dry eye candidates via a strip placed in the lower tear lake. Previously reported inconsistencies in the results may be in part due to the lack of standardization as to the methodology, e.g. the eye position during the test. The purpose of this study was to evaluate the effect of eye position on the ST score. . A ST was performed in a randomized fashion with and without anesthesia in three open eye positions (primary, superior and inferior) at 20° from each other. Palpebral aperture, age and a dry eye questionnaire (OSDI) were evaluated for correlation with the ST. In the 20 non-dry eye volunteers (n=20, ages 18-40, mean OSDI score 10.5), the ST results were, as expected, lower overall (p < .001) with anesthesia (11.33 ± 7.78 mm) than without (19.74 ± 2.83 mm). The inferior gaze position resulted in higher values (p < .03) than the other two positions, regardless of the use of anesthesia. No correlation was noted between the palpebral aperture, age, questionnaire and the ST. The ST seems to be influenced by the position of gaze. However, the mechanism for this, effect remains unclear. Further studies could focus on whether an inferior gaze of 20° compresses the tear film falsely, thereby elevating the tear volume. It is recommended that the clinician should adopt a standard eye position for the ST and that future reports provide specifics as to the methodology used.