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Dorota Helena Szczesna-Iskander, Slawomir Drobczynski; Non-invasive technique for dynamic measurement of tear film surface quality based on interferometry. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3867.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate the development of a new generation Lateral Shearing Interferometer (LSI) for non-invasive assessment of tear film surface quality (TFSQ) dynamics.
The LSI technique allows for objective in vivo evaluation of the tear film (TF) surface in the central area of a cornea or a contact lens by analyzing the shape of interference pattern. High sensitivity of this technique for subtle changes in TF dynamics has been demonstrated with a prototype (Szczesna et al. OVS 2009) whose several limitations hindered its potential to achieve full clinical utility. Recently, a new compact LSI was built. A HeNe laser (633nm) light source illuminates an area of 6 mm in diameter. The design of the interferometer meets the safety standards (ANSI Z136.1-2000). The LSI is fixed to a slit lamp base, the fixation target for the measured eye has been incorporated into the system, and a special head rest has been designed to minimize the head movements. Temporal dynamics of TF is recorded by a CCD camera with frequency of 29 frames per second.
Measurements on artificial eyes of radius from 7.8 to 8.5 mm (with and without astigmatism) as well as on over 50 subjects have been performed with the new LSI system as well as the previously used prototype. The slit-lamp based operation of the new LSI is more user friendly comparing to its predecessor. The new fixation target aligned with the measured eye rather than the fellow eye substantially improved eye’s stability during the measurement. The larger coverage area (6 mm vs 4 mm) and higher frequency of fringes determined by the optical wedge allow for more detailed analysis of the TFSQ and accurate assessment of TF post-blink stabilization phase and evolution of the TF break-up. The upward movement of the post-blink deterioration features is clearly observed (see figure).
The new improved generation of LSI enhances its clinical utility for non-invasive assessment of TFSQ and its dynamic properties on cornea and contact lenses. The new LSI provides basis for studying relationships between TF post-blink stabilization phase and TF related eye diseases.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Figure. Examples of interference patterns recorded with the new generation LSI: 0.10s (A); 0.34s (B); 0.68s (C); 1.00s (D) post-blink. The frames show the upward movement of the tear film features within the first second after the blink.
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