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Pre-corneal tear film thickness in humans measured with a novel technique.

ABSTRACT: The purpose of this work was to gather preliminary data in normals and dry eye subjects, using a new, non-invasive imaging platform to measure the thickness of pre-corneal tear film.Human subjects were screened for dry eye and classified as dry or normal. Tear film thickness over the inferior paracentral cornea was measured using laser illumination and a complementary metal-oxide-semiconductor (CMOS) camera. A previously developed mathematical model was used to calculate the thickness of the tear film by applying the principle of spatial auto-correlation function (ACF).Mean tear film thickness values (±SD) were 3.05 ?m (0.20) and 2.48 ?m (0.32) on the initial visit for normals (n=18) and dry eye subjects (n=22), respectively, and were significantly different (p<0.001, 2-sample t-test). Repeatability was good between visit 1 and 2 for normals (intraclass correlation coefficient [ICC]=0.935) and dry eye subjects (ICC=0.950). Tear film thickness increased above baseline for the dry eye subjects following viscous drop instillation and remained significantly elevated for up to approximately 32 min (n=20; p<0.05 until 32 min; general linear mixed model and Dunnett's tests).This technique for imaging the ocular surface appears to provide tear thickness values in agreement with other non-invasive methods. Moreover, the technique can differentiate between normal and dry eye patient types.

SUBMITTER: Azartash K

PROVIDER: S-EPMC3081798 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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Pre-corneal tear film thickness in humans measured with a novel technique.

Azartash Kaveh K Kwan Justin J Paugh Jerry R JR Nguyen Andrew Loc AL Jester James V JV Gratton Enrico E

Molecular vision 20110322

<h4>Purpose</h4>The purpose of this work was to gather preliminary data in normals and dry eye subjects, using a new, non-invasive imaging platform to measure the thickness of pre-corneal tear film.<h4>Methods</h4>Human subjects were screened for dry eye and classified as dry or normal. Tear film thickness over the inferior paracentral cornea was measured using laser illumination and a complementary metal-oxide-semiconductor (CMOS) camera. A previously developed mathematical model was used to ca ...[more]

PMID: 21527997

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Project description: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.

Project description:BACKGROUND:To evaluate the correlations between lipid layer thickness (LLT) and morphology and function of the meibomian glands in patients who were diagnosed as meibomian gland dysfunction (MGD) in different age groups. METHODS:Patients who have diagnosed as obstructive MGD were included in this prospective, cross-sectional study. Patients were divided into three groups: young (ages 20-39?years), middle-aged (ages 40-59?years), and older (aged ?60?years). All patients completed an Ocular Surface Disease Index (OSDI) questionnaire and were evaluated for LLT, tear meniscus height (TMH), noninvasive tear film break-up time (NI-BUT) measurement, invasive TBUT (ITBUT), corneal fluoresceinstaining (CFS) score, eyelid margin abnormalities, Schirmer I test, and MG function and morphology, by using the Keratograph 5 and LipiView interferometer. RESULTS:Two hundred and nine patients (209 eyes) were included. The median LLT of all patient was 57?nm (IQR, 36.5?nm), and the LLT values were significantly different among the young group (median, 51?nm; IQR, 23.5?nm), middle-aged group (median, 59.5?nm; IQR 46.5?nm) and older group (median, 62?nm; IQR, 42.5?nm) (P?=?0.033, Kruskal-Wallis test). In regression analyses controlling for confounder factors sex and MG loss, the LLT was positively correlated with age (??=?5.539, P?=?0.001). There was a negative correlation between LLT and MG dropout in the all (r?=?-?0.527, P?<?0.001), young (r?=?-?0.536, P?<?0.001), middle-aged (r?=?-?0.576, P?<?0.001), and older (r?=?-?0.501, P?<?0.001) groups. LLT was positively correlated with the MG expressibility in the all (r?=?0.202, P?=?0.003), middle-aged (r?=?0.280, P?=?0.044) and older (r?=?0.452, p?<?0.001) groups, but it was no statistical significance in the young group (r?=?0.007, P?=?0.949). CONCLUSIONS:The thickness of LLT was increased with age and significantly correlated with both MG secretion and morphology in middle-aged and older patients with obstructive MGD. LLT measurement is a useful screening tool for detecting obstructive MGD and age as an influential factor should be accounted for when interpreting the meaning of the LLT value. TRIAL REGISTRATION:NCT02481167 ; Registered 25 June, 2015.

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Pre-corneal tear film thickness in humans measured with a novel technique.

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Pre-corneal tear film thickness in humans measured with a novel technique.

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