Image-based quantitative analysis of tear film lipid layer thickness for meibomian gland evaluation

Abstract

BackgroundDry eye syndrome is one of the most common ocular diseases, and meibomian gland dysfunction (MGD) is the leading cause of evaporative dry eye syndrome. When the tear film lipid layer becomes thin due to obstructive or hyposecretory meibomian gland dysfunction, the excessive evaporation of the aqueous layer can occur, and this causes evaporative dry eye syndrome. Thus, measuring the lipid layer thickness (LLT) is essential for accurate diagnosis and proper treatment of evaporative dry eye syndrome.MethodsWe used a white LED panel with a slit lamp microscope to obtain videos of the lipid layer interference patterns on the cornea. To quantitatively analyze the LLT from interference colors, we developed a novel algorithm that can automatically perform the following processes on an image frame: determining the radius of the iris, locating the center of the pupil, defining region of interest (ROI), tracking the ROI, compensating for the color of iris and illumination, and producing comprehensive analysis output. A group of dry eye syndrome patients with hyposecretory MGD, dry eye syndrome without MGD, hypersecretory MGD, and healthy volunteers were recruited. Their LLTs were analyzed and statistical information—mean and standard deviation, the relative frequency of LLT at each time point, and graphical LLT visualization—were produced.ResultsUsing our algorithm, we processed the lipid layer interference pattern and automatically analyzed the LLT distribution of images from patients. The LLT of hyposecretory MGD was thinner (45.2 ± 11.6 nm) than that of dry eye syndrome without MGD (69.0 ± 9.4 nm) and healthy volunteers (68.3 ± 13.7 nm) while the LLT of hypersecretory MGD was thicker (93.5 ± 12.6 nm) than that of dry eye syndrome without MGD. Patients’ LLTs were statistically analyzed over time, visualized with 3D surface plots, and displayed using 3D scatter plots of image pixel data for comprehensive assessment.ConclusionsWe developed an image-based algorithm for quantitative measurement as well as statistical analysis of the LLT despite fluctuation and eye movement. This pilot study demonstrates that the quantitative LLT analysis of patients is consistent with the functions of meibomian glands clinically evaluated by an ophthalmologist. This approach is a significant step forward in developing a fully automated instrument for evaluating dry eye syndrome and for providing proper guidance of treatment.Electronic supplementary materialThe online version of this article (10.1186/s12938-017-0426-8) contains supplementary material, which is available to authorized users.

In vivo thickness measurement of the lipid layer and the overall tear film by interferometry

“…Specifically, the thickness of LL is typically less than 200 nm thick while one cycle of interference oscillation in the visible or near-infrared light corresponds to at least ~320 nm [11]. Alternatively, conventional methods estimate the LL thickness from the reflected intensity ratios among the different wavelengths (usually red, green, and blue, according to the RGB model of camera) [12][13][14][15]. These techniques are based on the fact that the interference signal from a thin film is a sinusoidal function of wave number (inverse of wavelength) for any given thickness.…”

Efficacy of 0.05% cyclosporine A on the lipid layer and meibomian glands after cataract surgery: A randomized, double-masked study

“…Decreased LLT has been associated with the instability of the lipid layer, and MGD could contribute to the emergence of ocular surface disease (OSD) [5,26]; therefore, in this study, the significant difference in postoperative LLT between eyes treated with and without CsA could be attributed to the improvement in the ocular surface caused by postoperative CsA. The Schirmer's I test results did not show significant differences between the two groups.…”

“…As 0.05% CsA may decrease MG inflammation, the symptoms of MGD and MG plugging may decrease owing to the highly specific immunomodulating process affecting T lymphocytes; 0.05% CsA can effectively control ocular surface inflammation and treat MGD [ 23 – 25 ]. Decreased LLT has been associated with the instability of the lipid layer, and MGD could contribute to the emergence of ocular surface disease (OSD) [ 5 , 26 ]; therefore, in this study, the significant difference in postoperative LLT between eyes treated with and without CsA could be attributed to the improvement in the ocular surface caused by postoperative CsA.…”

An imaging system integrating optical coherence tomography and interferometry for in vivo measurement of the thickness and dynamics of the tear film

“…The TDF system has a circular field of view of 3 mm and a spatial resolution of 5 μm in x–y plane. The LL thickness is quantified and graded by identifying the dominant colors in the interference patterns [ 12 , 38 ]. White reflectance corresponds to thicknesses below 30 nm, grey up to 60 nm, yellow up to 90 nm, brown up to 135 nm, and blue up to 180 nm.…”