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Film Stability (film + stability)

Distribution by Scientific Domains
Medical Sciences100%

Kinds of Film Stability

  • tear film stability
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    Selected Abstracts

    Numerical analysis of interferograms for evaluation of tear film build-up time

    OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 3 2009
    Dorota H. Szczesna
    Abstract The lateral shearing interferometer was applied to the in vivo dynamic investigation of the external surface of the pre-corneal tear film after an eye blink. Sequences of interferograms were recorded at a sampling frequency of 25 Hz. Immediately after every eye blink, a bright pattern was observed under the interference fringes. This disappeared after a short time interval (around 0.5,2 s): smooth interference fringes were then observed, corresponding to the creation of a smooth anterior optical surface over the cornea. The purpose of this study is to describe in detail the kinetics of pre-corneal tear film stability and to propose quantitative measures of the stabilisation process in healthy eyes during the 3 s period after a blink. Two methods of quantitative assessment of the tear film build-up time are presented. The first is based upon the evaluation of the inhomogeneity of the background of the interferogram; the second evaluates the orientation of the structure of the background by the analysis of the zero order of the Fast Fourier Transform (FFT) spectrum. The quasi-vertically oriented bright line patterns observed in interferograms immediately after a blink and the mirror-symmetry of their tilts for right and left eyes indicate that the pattern is related to the wiping movements of the upper eyelids during the eye blink. [source]

    The effect of elevated dietary cholesterol on pulmonary surfactant function in adolescent mice

    PEDIATRIC PULMONOLOGY, Issue 5 2008
    K.C. McCrae PhD
    Abstract It has been established that phospholipids and cholesterol interact in films of pulmonary surfactant (PS). Generally it is thought that phospholipids increase film stability whereas cholesterol increases film fluidity. To study this further, we modified dietary cholesterol in mice which received either standard rodent lacking cholesterol (sd), or high cholesterol (2%) diet (hc) for 1 month. Phospholipid stability was investigated by a capillary surfactometer (CS), which measures airflow resistance and patency. PS was collected by bronchiolar lavage and centrifuged to obtain the surface-active film (SAF). Results showed that the hc-SAF had significantly more cholesterol than sd-SAF. CS analyses at 37°C showed no significance differences in airflow resistance between hc-SAF and sd-SAF. However, at 37°C, sd-SAF showed greater ability to maintain patency compared to hc-SAF, whereas at 42°C hc-SAF showed patency ability similar to sd-SAF. The results suggested that increased cholesterol in hc-SAF induced less stability in the SAF possibly due to cholesterol's fluidizing effect on phospholipids at physiological temperatures. Pediatr Pulmonol. 2008; 43:426,434. © 2008 Wiley-Liss, Inc. [source]

    3445: Evaluation, diagnosis and grading of severity of MGD

    ACTA OPHTHALMOLOGICA, Issue 2010
    AJ BRON
    Purpose To evaluate current diagnostic tests and make future recommendations. Methods An evidence-based review of procedures. Results MGD is a common symptomatic disorder leading to associated ocular surface disease including evaporative dry eye. A two stage diagnostic approach is recommended including an assessment of meibomian function based on lid morphology, gland mass, expressibility, lipid layer appearance and tear evaporation. A diagnosis of dry eye is based on measures of tear production and clearance, tear osmolarity, tear film stability and the presence of ocular surface changes revealed by tissue staining and inflammatory biomarkers. Quantification of MGD depends on grading meibum quality and expressibility. Newer, quantitative methods will make grading more accurate in the future and include quantitative meibomian expression, non-invasive meibography, confocal microscopy, video-interferometry and the use of inflammatory biomarkers. Meibomian gland dropout can be to monitor and stratify MGD in clinical trials. Conclusion A provisional severity rating of MGD and MGD-related disease has been proposed as a guide to the selection of treatment and the monitoring of disease progression. [source]

    3224: Chitosan in the treatment of dry eye

    ACTA OPHTHALMOLOGICA, Issue 2010
    L SCHMETTERER
    Purpose To demonstrate the safety and efficacy of a new eye drop formulation containing a novel thiolated biopolymer, namely chitosan-N-acetylcysteine, in a number of pre-clinical tests. It is postulated that interaction between thiol groups of the topically applied chitosan-N-acetylcysteine and cysteine-rich mucin (MUC5AC) increases polymer residence time on the ocular surface and tear film stability. Methods The efficacy of isotonic and buffered chitosan-N-acetylcysteine eye drops was evaluated in two different dry eye mouse models. The dosage dependent ocular residence time and biodistribution were investigated in a rabbit model using microPET technology. Long-term irritation and delayed-type hypersensitivity tests with chitosan-N-acteylcysteine eye drop formulation were conducted in rabbits. Results In both dry eye studies mice treated with chitosan-N-acetylcysteine showed decreased expression of ocular surface mRNA of IL-,, IL-10, IL-12,, and TNF, indicating that the formulation may have protective ocular surface properties. The residence time of chitosan-N-acetylcysteine eye drops on the ocular surface of rabbits was increased (detection up to 22h). Results of a long-term ocular irritation study in rabbits demonstrate that the novel formulation is well tolerated and non-irritant to the eye. Conclusion Based on the promising pre-clinical study results both in terms of efficacy and safety a clinical phase 1 trial is scheduled in the near future. Commercial interest [source]

    4133: Dry eye and human tear lipid compositional, conformational and functional relationships using spectroscopy

    ACTA OPHTHALMOLOGICA, Issue 2010
    D BORCHMAN
    Purpose Knowledge of the relationships among composition, conformation and function of tear film lipids could facilitate the development of therapies to alleviate symptoms related to meibomian gland dysfunction (MGD) and to diagnose the disease. Toward this goal, we used spectroscopic approaches to assess tear lipid composition and conformation relationships with age, sex and meibomian gland dysfunction. Methods Spectra of meibum from 41 patients diagnosed with MGD (Md) and 27 normal donors (Mn) were acquired. Results 1H-NMR spectra showed cholesterol esters were found to decrease by 21% with MGD. The number of double bonds/ester increased with age and MGD which indirectly relates to tear film stability. With age, the amount of CH2 groups increased twice as much as the C=C moieties and the C=C/CH2 and CH3/CH2 ratios were related to lipid order and indirectly related to meibum delivery. With the use of MALDI-TOF MS, we quantified and identified lipid components in Mn and Md such as cholesterol, hydrocarbons and wax esters with a sensitivity of 9 pmoles for each analyte. Sixty-nine of the 189 resolved peaks were unique to Md spectra compared to Mn spectra and were not due to waxes. Extra peaks in Md spectra may arise from increased lipid synthesis, bacteria or cellular debris. Conclusion It is reasonable that as the lipids become more ordered and more viscous with Md, less lipid flows out of the meibomian gland orifice and more casual lipid is present on the lid margin. The age- and disease-related changes in the physical and chemical characteristics of meibum lipids suggest that the C=C/CH2 and CH3/CH2 ratios may be more important than quantity in relation to tear film stability. [source]

    Tear functions in patients with pinguecula

    ACTA OPHTHALMOLOGICA, Issue 3 2001
    Halit Oguz
    ABSTRACT. Purpose: To investigate the tear flow, tear film stability and condition of mucus in patients with pinguecula. Methods: The Schirmer I and ferning tests were performed and break-up time (BUT) was determined in 57 patients with pinguecula [random eyes; 34 males and 23 females, 18 to 70 years of age (mean±SD: 39.1±13.5 years)] and in 57 age-matched subjects (control) [random eyes; 35 males and 22 females, 11 to 70 years of age (mean±SD: 37.8±15.2 years)], and the test results were statistically analysed. Results: The mean Schirmer test value was 22.72±12 mm in the eyes with pinguecula and 22.7±8.5 mm in the control eyes. There was no statistically significant difference (t=0.01, p=0.99) between the groups. The mean BUTs were 11.42±6.89 s in the eyes with pinguecula and 15.46±5.85 s in the control eyes. Comparison of BUTs between the groups revealed a statistically significant difference (t=3.37, p=0.0010). Also, ferning types were found to be significantly abnormal in the eyes with pinguecula (p<0.01). Conclusion: The alteration in the mucin layer is a possible change inducing pinguecula formation, or it may reflect an already existing pathology in the cells on the ocular surface. [source]