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JH Wang, D Fonn, TL Simpson, L Jones; Pre-corneal and pre- and post-lens tear film thickness measured with Optical Coherence Tomography . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3078.
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Purpose:To demonstrate the feasibility of measuring the pre-corneal tear film thickness and pre- and post-lens tear film thickness using the Optical Coherence Tomography (OCT). Methods:Central corneal thickness (C1) which included tear film (T) of both eyes of 27 non-lens-wearers was measured using OCT after calibration. The age range of the subjects was 21-46 yrs with a mean horizontal K-reading 8.00mm. Rigid gas permeable lenses with base curves 0.3-0.5mm steeper than flattest K were fitted in order to measure real corneal thickness (C2) independently of the post lens tear film. T was calculated by using T=C1-C2. To measure pre- and post-lens tear film thickness, a lotrafilcon lens and an etafilcon lens were fitted on both eyes of 20 subjects from the group. Central soft lens thickness (L1) which included the pre-lens tear film (P) was measured in situ and central lens thickness was measured again in saline in a wet cell (L2). P was calculated by using P=L1-L2. Meanwhile, central corneal thickness (C3) including post-lens tear film (PLTF) was measured during lens wearing. PLTF was calculated by using PLTF=C3-C2. Results:The mean (±SD) pre-corneal tear film thickness was 3.3 ± 1.2µm (range: 0-6.9). The pre-lens tear film thickness was 3.3 ± 1.9µm and 4.0 ± 2.1µm (mean ± SD) (paired t-test: p=0.52) on lotrafilcon lenses and etafilcon lenses respectively. The post-lens tear film thickness was 4.7 ± 3.0 µm and 5.0 ± 2.7µm (paired t-test: p=0.08) under lotrafilcon and etafilcon lenses respectively. Post hoc tests (Tukey HSD P<0.05) showed that pre-corneal and pre-lens tear films were equivalent and each was different (thinner) from the post-lens tear film. Conclusion:OCT allows rapid and non-invasive measures of the thickness of the pre-corneal and pre-lens tear film as well as the post-lens tear film. There was no difference between lenses for both pre- and post-lens tear film thickness although the post-lens tear film was greater than the pre-corneal and pre-lens tear films. (This study is partly support by COETF)
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