PURPOSE

To investigate infant tear film secretion and protein profile, and to compare major tear proteins, such as immunoglobulin A, lactoferrin, and lysozyme, with those of adult controls.

METHODS

Tears were collected, with a cellulose rod, from 40 healthy infants (19 female infants and 21 male infants, gestational duration: 39.71 ± 1.27 weeks) within 48 hours of birth and 22 adults (10 female infants and 12 male infants, mean age: 24.95 ± 3.63 years). A second collection was obtained from 14 of the infants (8 female infants and 6 male infants, postnatal age: 7.76 ± 6.14 weeks). The tear volume was measured, and protein in the samples was analyzed by Bradford assay and gel electrophoresis.

RESULTS

Median tear volume (interquartile range) was 0.5 μL (0.6-2 μL) for newborn infants, 2.5 μL (1.4-7.75 μL) for these infants at an older age, and 6 μL (2.73-12.75 μL) in adults (P < 0.001, Kruskall-Wallis test). Immunoglobulin A concentration was significantly lower in newborns (P < 0.001, analysis of variance). Lipocalin was present in 36% of the newborn tear samples, whereas serum albumin was found in 86%. Mean protein concentration (μg/μL ± SD) was 10.95 ± 5.51 in the newborns, 12.93 ± 3.99 in the older infants, and 13.04 ± 3.46 in the adults (P > 0.5, analysis of variance).

CONCLUSIONS

This is the first study reporting an investigation of unstimulated infant tears, using a noninvasive collection method. Tear protein content demonstrated that the infant tear film is different to that in adults.