The thickness of the human precorneal tear film: evidence from reflection spectra.

摘要: Purpose Interferometric methods have considerable potential for studying the thickness of layers human tear film and cornea because their ability to make noninvasive, accurate, rapid measurements. However, previous interferometric studies by Prydal Danjo yielded values near 40 11 microm, respectively, considerably greater than estimates made invasive 4 8 microm. Using a modified version Danjo's method, interference effects from were studied, with aim correlation known structure optical properties hence determining most probable value thickness. Methods Reflectance spectra measured at normal incidence. These show oscillations whose maxima correspond constructive between light reflected air surface some deeper surface. The frequency these spectral is proportional layer second Therefore, Fourier analysis reflectance can be used determine cornea. In main experiment, 36 low-resolution obtained six eyes measuring up 100 Control experiments included measurements time course changes high-resolution 1000 Results For in range 1 strongest peak transform was 3 microm (range, 1.5-4.7 microm) beneath 20 55 50-59 all spectra; none Prydal's This 55-microm consistent reflection basement membrane epithelium. Time after blink that 3-microm not an artifact. High-resolution gave 510 corresponding complete (plus film). had contrast similar peak. Conclusions did confirm estimate approximately Nor there prominent peaks except cases reflex tears. Because aqueous-mucus boundary would expected weaker epithelial surface, unlikely aqueous (rather proposal corresponds front supported demonstration back Thus, current evidence consistently supports precorneal film.