Scanning electron microscopy (SEM) and energy dispersive analysis (EDXA) of human tear fern patterns

E. I. Pearce*, A. Tomlinson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Purpose. The patterns obtained when tears are allowed to dry on a glass surface, often described as tear fermng. are used as i diagnostic aid in evaluating dry eye patients. It has been speculated that the abnorm;.l terns obtained are indicative of the differential levels of proteins, mucins and salts. Previous effoits to analyse the components of tear ferns have found the elements Na. K CI and S are present. The spatial resolution ol these components has not been mad.-. This study makes use of SEM coupled vviih EDXA to looks at the morphology and relative elemental composition of these structures. Methods. Samples wen collected from normal individuals using a glass capillary drawn and sterilised in a fia ne. The tear sample, typically Ijal, was ejected onto a clean glass microscope slide md allowed to air dry. The tear fern patterns obtained were observed under a whit : light microscope using normal illumination and were found to be characteristic of those reported for normal individuals. The tear ferns were then examined with a JEOL 840A SEM and further details of the fern microstructure was obtained. A Trace r EDXA system coupled to the SEM was used to selectively analyse the elemental maki-up of the structures observed. Results. The dried tears were found to show thret types of micro-structure. The predominant type were classic fern shaped structure; commated by sodium chloride The second type were small cuboidal crystals (2-5 u.m n .size) compo.sed of potassium chloride. The third type of structure, always found at tht outer edge of the tear drop, was a smooth Film with occasional cracks. This film w is found to be the only structure with detectable levels of sulphur, indicating the presence of protein and/or mucin. Conclusions. It has been speculated that mucins and p oteins are intimately involved in the formation of the tear ferns and that alterations m the quantity or quality of these macromolecuie-; affects the pattern observed in disease states. In this study mucins and proteins were only found at the margin of the dried lear drop. It is likely therefore, mat it is the levels of salts that play the major role in the ormation and appearance of the tear fern.
Original languageEnglish
Pages (from-to)S153
JournalInvestigative Ophthalmology and Visual Science
Volume38
Issue number4
Publication statusPublished - 1997

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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