Tear film stability and immunoglobulin a variation during the day

Abstract

Tear film stability and immunoglobulin A variation during the day A. Puinhas1, M. Lira1, S Franco1 and M P Sampaio2 1.Centre of Physics (CFUM), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal. 2. Centre of Molecular and environmental Biology (CBMA), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal. .

Currently, there are more than 100 million contact lenses (CL) wearers worldwide and according to the International Association of Contact Lens Educators (IACLE), it is expected that this number increase to 150 million.. This has led to a continual introduction of new materials that aims to bring greater comfort, better ocular health and improved visual quality to their users. In spite of this advances several studies reveal changes in ocular physiology and ocular discomfort related with CL wear. It is important to evaluate whether these physiological changes and ocular discomfort are actually resulting from CL wear, or if there are pre-existing variables in ocular physiological cycle that can also occur in non-contact lenses wearers. Biochemical parameters, like proteins as immunoglobulin A (IgA), and tear film properties are important factors to consider. In this work, the stability of the tear film and protein content were evaluated, analyzing also the variation of these parameters in two different times of the day. Twenty healthy and young individuals, with an average age of 24±2.5 years without dry eye symptoms, were included in the study. In a controlled laboratory setting, on the same day for each individual, morning and afternoon Non Invasive Break Up Time (NIBUT) measurements were performed with a Tearscope Plus equipment. Tear samples were collected with microcapillarity tubes and stored at -80ºC. Protein profile was analyzed by desnaturing polyacrylamide gel electrophoresis Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and native electrophoresis polyacrylamide gel electrophoresis (PAGE). IgA were quantified by Enzyme Linked Immuno sorbent assay (ELISA). Tear film stability and protein profile showed no significant differences between the left and right eye, but exhibited distinct protein profile and NIBUT values between morning and afternoon. For NIBUT, the mean values obtained were17±22.3 s and 12.79±4.25 s, in the morning and in the afternoon respectively and this difference is statistically significant (p=0.000). There is a pattern on daily IgA variation in tear with a concentration higher in the morning (2.656±0.625 mg/ml) than afternoon (2.116 ±0.789 mg/ml) being this difference statistically significant (p  0.05). The tear film stability and IgA decreases on afternoon, usually the period of the day on which the patients show eye discomfort, even when they do not wear CL. We conclude that there are daily variations in composition and properties of the tear film that may contribute for that. Also these results may indicate that changes in composition of tear film do not necessarily have to be caused by the CL wear or by the presence of ocular or systemic pathologies.