Classification system of clearance of lipids in human tears according to optical coherence tomography parameters

Purpose: To establish a classification system for clearance of lipids (CoL) in human tears according to optical coherence tomography (OCT) parameters. The purpose of this classification system is to provide a uniform and objective assessment of the dynamics of tear lipids with a novel technique of contrast-enhanced optical coherence tomography imaging in evaluation of CoL. Methods: The CoL appearance grading scale contains a set of OCT images standards illustrating a range of various concentrations of lipids in human tears (0.5%, 0.25%, 0.125%, 0.06%, 0%). These standards consist of OCT scans of the lower tear meniscus (LTM) at baseline and after instillation of a lipid-based tracer (containing different concentrations of lipids) or saline. Fifty-one OCT images were evaluated and scored by three cornea subspecialists in a masked fashion according to the scale. Results: High inter-observer agreement was found using the scale to classify the CoL, with respect to the appearance of OCT reflectivity (CoL +0.90, interclass correlation coefficient for consistency using a 2-way mixed effect model). Conclusions: The CoL appearance grading system is a simple, reproducible system for classifying the OCT appearance of turnover of lipids in human tears.