Fachbereich Veterinärmedizin



    Interferometrie, Meibometrie und biochemische Analyse der Lipidschicht des Tränenfilms beim Hund (2012)

    Ewert, Anna Maria (WE 20)
    Berlin, 2012 — X, 119 Seiten
    URL (Volltext): http://www.diss.fu-berlin.de/diss/receive/FUDISS_thesis_000000040375
    Klinik für kleine Haustiere

    Oertzenweg 19 b
    Haus 1
    14163 Berlin
    Tel.+49 30 838 62356 Fax: +49 30 - 838 460 157
    email: kleintierklinik@vetmed.fu-berlin.de

    Abstract / Zusammenfassung

    All three parts of the preocular tear film are essential for eye health. They protect and nourish
    the cornea and optimize eyesight. The mucin layer is formed by goblet cells, the aqueous
    layer in the lacrimal glands and the lipid layer is predominantly established in the meibomian
    glands in the shape of an oily secretion (meibom secretion).
    A hypovolemic tear deficiency which can cause “dry eye”, Keratoconjunctivitis sicca, due to
    a quantitative deficiency of the aqueous layer, has long been able to be recognized and treated
    in veterinary ophthalmology utilizing suitable diagnostics. A qualitative tear deficiency can
    also lead to “dry eye” as a result of hyper evaporation of the aqueous parts and is caused by a
    reduced, lacking, and in its composition impaired lipid layer. While human medicine has
    engaged in research of the lipid layer as well as diagnostics and therapy of this serious disease
    for decades, this type of “dry eye” is widely unknown in veterinary medicine. In animals and
    especially in dogs there is a lack of scientifically reliable diagnostic methods for an
    examination of the lipid layer as well as information concerning the composition of the canine
    lipid layer. The evaporative “dry eye” of the dog is often not recognized. In order to close this
    gap the aim of this study was to verify the procedure of interferometry widely utilized in
    human medicine using Tearscope-plus® to assess the lipid layer utilizing a large dog
    population concerning its applicability and reproducibility. Meibometry by means of
    Meibometer® MB 550, a procedure to quantify the meibom secretion was also to be tested on
    a larger scope of patients. Furthermore the meibom secretion of the dog was characterized in
    its biochemical composition for the first time.
    Applicability of interferometry and meibometry could be tested on dogs successfully. The
    examination is admitted well without exception and is carried out within seconds. During the
    evaluation of the lipid layer of the dog using Tearscope-plus® three of six interference images
    also seen in humans as well as three additional mixed images were observed. In 98 dogs (196
    eyes) a homogenous interference image (35.2%), a wavy pattern (25.5%) and interference
    colors (18.9%) were observed most commonly. These patterns appear in humans as well and
    point to a stable, physiological lipid layer of 40 to 590 nm thickness. Meibometry by means of
    Meibometer® MB 550 was carried out in 56 animals (112 eyes) and amounted to 299.47 MU
    (meibom units) ± 170.4 MU. The results presented here are clearly above existing studies on
    humans and dogs. Although measuring meibometry could be carried out in all patients, a
    broad distribution of results over the course of a day as well as a week currently prevents
    reproducibility of this method. Results of biochemical analysis of the meibom secretion using
    HPLC – MS (High Pressure Liquid Chromatography with Mass Spectrometry) are promising.
    Meibom secretion of the dog is qualitatively very similar to the secretion found in humans,
    however quantitative differences were found. The lipids found in canine meibom secretion
    characterized for the first time are cholesterol, cholesterolester, wax ester, diacyl- and
    triacylglycerols as well as so-called OAHFAs ((O-acyl)-omega-hydroxy-fatty-acids).
    Based on the results presented in this study, future studies concerning the lipid layer of the
    tear film should not only examine healthy but also animals of bad health. This enables a
    differentiation between physiological and pathological results both on a clinical diagnostic as
    well as a biochemical level and may lead to improvements of diagnostics and therapy of the
    evaporative “dry eye”.