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A Touhami, E Goto, SC G Tseng; Kinetic Analysis of the Tear Interference Image in Patients with Demodex Blepharitis . Invest. Ophthalmol. Vis. Sci. 2002;43(13):100.
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Purpose:Previously we have developed a kinetic analysis of tear interference images and noted that lipid tear deficiency (LTD) can be distinguished form aqueous tear deficiency (ATD) and normal. We investigated the pattern of spread and stability of the lipid tear film in patients with demodex blepharitis, which is frequently associated with meibomian gland dysfunction (MGD). Methods:Using the instrument of DR-1 (Kowa, Tokyo, Japan), we captured sequential images of the tear interference pattern in the central 8 mm in diameter of the cornea during consecutive normal complete blinks. These kinetic data were then analyzed by image analysis software to measure the spread and stability of the lipid film. Using this technique, we studied 8 patients with demodex blepharitis, diagnosed by microscopic counting of 8 lashes randomly sampled in two eyes. Aqueous tear function was assessed by fluorescein clearance test. Results:None of these 8 patients showed a normal lipid tear film, which should spread in a horizontally propagating pattern, and reach a stable image within 0.36 ± 0.22 sec. The thickness should be thin and uniform and the subsequent images should remain stable during the rest of the normal inter-blink time. In contrast, four patients showed LTD pattern, which spread slowly with vertical streaking, and remained too thin and unstable. Two patients, which also had ATD by fluorescein clearance test, showed a pattern of ATD, in which the lipid film spread at the speed between the normal and LTD patients, resulting in a thicker lipid film with horizontal pattern on the inferior cornea, while the thickness of the lipid film on the remaining cornea was thinner than normal and distributed at times in a vertical streaking pattern. The rest showed an as-yet uncharacterized pattern, suggesting the inclusion of abnormal lipids. Conclusion:The above findings suggest that patients with demodex blepharitis tend to present with abnormal lipid tear film, which is characterized by deficient or abnormal lipid production. Further investigation is under way to delineate the role of demodex infection in MGD.
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