Microdesiccates produced from normal human tears display four distinctive morphological components

Desiccation of human tears on glass surfaces results in fern-like crystalloids. This phenomenon has been associated with tear normality (Tear Ferning Test, TFT) and is used as a diagnostic aid to evaluate patients with Dry-Eye disease. However, TFT is focused on the assessment of only a minor fraction of desiccated tear samples and considers only the relative abundance and density of fern-like crystalloids. The aim of this study was to characterize morphologically entire desiccated micro volumes of tears from healthy donors. Tear samples were collected from 23 healthy young adult volunteers. Tear aliquots (1-3 μL) were allowed to dry on glass surfaces under ambient conditions of temperature (15-25°C) and relative humidity (40-45%). Dry samples were analyzed by dark-field microscopy. Morphometric data were acquired with Image J software. Tear volume was positively correlated with both area and time of desiccation. Morphological features of multiple microdesiccates produced from a single subject displayed striking similarities whereas tear microdesiccates from different healthy subjects displayed consistent differences but shared a common general design. This design may be mostly represented by the occurrence of four distinctive zones, named as zones I, II, III and Transition band. The main features of these zones are described.