[Evaluation of tear film stability by means of laser interferometry]. / Pomiar stabilnosci filmu lzowego za pomoca prototypowego interferometru laserowego.

PURPOSE: The paper presents a new method for evaluation of the tear film stability on the human eye. METHODS: The tear film distribution on the cornea is measured by the lateral shearing interference technique. The eye is kept open during approximately a two-minute recording, when the blinking has to be prevented. Continuous recording and viewing of interferograms enables registration of the changes in disturbances of interference fringes during elapsed time. The changes in fringes are caused by evaporation of tears from the ocular surface and appearance of the breakups. CONCLUSIONS: The noninvasive tear breakup time (NITBUT) can be evaluated by comparing the recorded consecutive interferograms.

Application of twyman-green interferometer for evaluation of in vivo breakup characteristic of the human tear film.

The paper presents an interferometric method of assessing the in vivo stability of the precorneal tear film. To observe dynamic effects on a human cornea the Twyman-Green interferometer with television frame speed digital registration synchronized with a laser flash was used. The instrument was applied to the human cornea in vivo. The results of the experiment, both tear film distribution and its dynamics, are presented. The proposed interferometric setup can be used to evaluate the breakup characteristics of the tear film, its distribution, and to examine its dynamic changes. The breakup profiles and their cross sections calculated from the interferogram analysis are presented. The depth of recorded breakup, calculated on the basis of interferogram analysis, amounts to about 1.5 µm. The proposed method has the advantage of being noncontact and applies only a low-energy laser beam to the eye. This provides noninvasive viewing of human cornea in vivo and makes it possible to observe the kinetics of its tear film deterioration. © 1999 Society of Photo-Optical Instrumentation Engineers.

Analysis of shearing interferograms of tear film using fast fourier transforms.

A new method for evaluating tear film stability on the human eye is reported. The tear film distribution on the cornea is measured by the lateral shearing interference technique. The eye is kept open during approximately a 2-min recording, when blinking has to be prevented. Continuous recording and viewing of interferograms allows the changes in disturbances of the interference fringes to be registered during elapsed time. The changes in fringes are caused by the evaporation of tears from the ocular surface and appearance of the breakups. For precise and repetitive assessment of the tear film breakup time, a fast fourier transform (FFT) is applied to consecutive interferograms. Larger fringe disturbances result in wider Fourier spectra. The tear breakup time can be evaluated noninvasively by comparing the value of the second momentum of Fourier spectra calculated from the consecutive interferograms. © 1998 Society of Photo-Optical Instrumentation Engineers.