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Jannick P Rolland-Thompson, Jinxin Huang, Holly Butler Hindman; IN VIVO MEASUREMENT OF TEAR FILM DYNAMICS WITH OPTICAL COHERENCE TOMOGRAPHY AND MAXIMUM-LIKELIHOOD ESTIMATION. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6179.
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© ARVO (1962-2015); The Authors (2016-present)
Understanding the dynamics of the tear film after a blink is of great importance to advance the management of Dry Eye Disease. The purpose of this study is to investigate the feasibility of using a customized imager to evaluate the tear film dynamics in vivo, by simultaneously estimating the thickness of the lipid and aqueous layers of the tear film through an optical approach.
The imager consists of an advanced optical coherence tomography and a robust maximum-likelihood estimator, which has been validated using tear film phantoms. To evaluate the tear film dynamics in vivo, a chinrest with translational adjustments was developed for a rough alignment of the subject with the imager. A finer alignment has been realized through a dual axis galvo-scanner, which performs rapid scans over the corneal surface and identifies the corneal apex location. The scanner then immediately steers the light beam to the apex area and scans over a 0.5 mm by 0.5 mm area with 30 by 30 sampling points. Due to the curvature of the cornea and the telecentric scanning scheme of the current system, only the point with the maximum spectrum intensity is selected and processed for an estimation, which is considered to have a normal incidence of light. In the data acquisition process, the subject is asked to have a complete blink and then keep the eye open for 10 seconds.
A tear film dynamics curve acquired from an Asian male (normal subject, age 29) is shown in Figure 1, which illustrates the temporal change of both the lipid and aqueous layer thicknesses in a 10 seconds time frame after a blink, in vivo. Right after a complete blink, the lipid layer gets thicker rapidly with a thickening rate of 12 nm/s, and it stabilizes after about 2 seconds; the aqueous layer gets thinner gradually, from about 5 micron right after a blink down to about 2 micron in 10 seconds, with an average thinning rate of 0.3 micron/s.
The temporal change of the simultaneous acquisition of the lipid and aqueous thicknesses has been successfully measured in vivo. The customized tear film imager is shown to be feasible to investigate the tear film dynamics. Future work will integrate a scanning scheme that will allow the normal incidence of the scanning beam along the corneal surface, enabling measurements of thickness maps.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Thickness dynamics of (a) lipid layer and (b) aqueous layer after a blink
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