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S. M. Grenon, D. R. Korb, C. A. Blackie, W. Weber, R. Chinnock; A Unique Ocular Surface Interferometer (OSI) to Measure and Evaluate Lipid Layer Thickness (LLT). Invest. Ophthalmol. Vis. Sci. 2010;51(13):3382.
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© ARVO (1962-2015); The Authors (2016-present)
To provide an ophthalmic imaging device intended for clinical use on dry eye patients to capture, archive, manipulate and store digital images of specular (interferometric) observations of the tear film, which can be visually and photographically monitored and numerically defined and documented.
The unique LipiView® Ocular Surface Interferometer (OSI) acquires the specularly reflected colors from the tear film. A spatially modulated light source allows removal of unwanted background images and stray light. Metrological RGB video data is acquired, frames and region of interest are selected automatically to remove blinks and artifacts, background images are removed, and statistical data are compared to a master look-up table (LUT) for lipid layer grading. The LUT is calculated using advanced principles of optical physics with commercial and custom modeling tools, using precise calibrations of the white light source and camera spectral responses, along with published refractive index and dispersion values for lipid and aqueous layers. This LUT has a spiral locus in RGB space. The processed output is expressed as Interference Color Units (ICUs), which correlate with Lipid Layer Thickness (LLT), using a kinemetric distribution. A previous report on the use of an early prototype OSI in routine clinical practice, demonstrated that LLT measurements correlate significantly with patient symptoms of dry eye.
The processed instrument data matches well to the expected spiral of RGB values of the LUT, demonstrating agreement with theory. In addition a previous study on an early prototype OSI indicates the clinical suitability and applicability of this imaging technology.
The LipiView® OSI is viable as an objective tool for the evaluation of patient LLT. This imaging device is likely to significantly impact the routine clinical diagnosis and treatment monitoring of lipid deficient evaporative dry eye, since the methodology allows for ready incorporation of the LipiView® instrument to routine clinical practice.
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