[Imaging of the microarchitecture and dynamics of the break-up phenomena of the preocular tear film with the aid of laser scanning microscopy].

BACKGROUND

Sufficient and regular wetting of the cornea with a normal preocular tear film is an essential requirement for the accurate visual functioning of the eye. Multiple factors may cause tear film instability. Measuring the break-up time of the preocular tear film is a necessary, clinically reliable means for evaluating tear film stability. We designed a new instrument to observe the preocular tear film at high magnification which can contribute to the in vivo imaging of the physiological and pathophysiological dynamics of the tear film and its break-up phenomena.

MATERIALS AND METHODS

To image the tear film phenomena at sufficient magnification (x200) we used a confocal laser scanning microscope. Modification of an additional adaptor allows the tear film to be imaged at high magnification. This study evaluated the dynamics and microarchitecture of the break-up phenomena in the preocular tear film of normal patients and patients with "dry eye".

RESULTS

Laser scanning microscopy allows high magnification imaging of the preocular tear film and evaluation of a number of break-up mechanisms. The dynamics and structure of the tear film was analyzed and documented. Based on our observations we formulate a new hypothesis on the break-up mechanism of the preocular tear film caused by alterations in the epithelial surface, for example, an elevation or tear film microparticle. By evaluating video sequences in the fluorescence and reflection modus of the laser scanning ophthalmoscope we also found early thinning of the aqueous layer simultaneously with an intact lipid layer covering the aqueous layer.

CONCLUSION

Additional criteria result from using high-magnification microscopy, for example, laser scanning microscopy. This method reveals more microstructures of the corneal surface and the preocular tear film. The morphological representation of break-up phenomena leads to a better understanding of the underlying mechanisms and can be used for further investigations. Confocal laser scanning microscopy supplements the examination facilities and can be used in addition to slit lamp microscopy and to diagnose "dry eye".