Integrated multimodal metrology for objective and noninvasive tear evaluation.

The clinical tests used to assess tear film and diagnose dry eye are invasive and produce results that are different from natural tear characteristics. There is a need to objectively and noninvasively assess tear parameters under controlled environmental circumstances to refine dry eye diagnosis and therapy. We have developed multimodal tear imaging systems integrated in a chamber in which individual environmental factors can be precisely varied to investigate their impacts on tear parameters. With the custom-built high-resolution wavefront sensor combined with placido disc, it is possible to objectively detect two-dimensional tear breakups in real time and evaluate its impact on visual quality. Micrometer ultra-high resolution optical coherence tomography (OCT) enables us to quantify thickness and volume of the tear over the cornea and tear menisci. The ocular surface imaging ellipsometer uses polarized illumination from which both the lipid refractive index and thickness can be measured at a very high resolution. Using an enhanced thermal camera, we measure the ocular surface temperature noninvasively, which makes it possible to study spatial and temporal changes in tear evaporation. The multimodal deployment of these four components in the controlled chamber will assist in better differentiating the various clinical dry eye entities and will lead to the development of specific dry eye treatments. Copyright Â