Interferometric measurements of dynamic changes of tear film

Abstract

Tear film stability plays an important role in the quality of vision. We present an interferometric method for assessing the stability of precorneal tear film in real time. A lateral shearing technique is applied as a noninvasive and sensitive method for investigating tear film stability and the smoothness of the tear film surface by quantitative evaluation of the interference fringe pattern. The evaporation of tears and the appearance of tear film break-up between blinks cause changes in the fringe geometry. For quantitative assessment of the fringe smoothness and consequently of the tear film structure, the fast Fourier transform (FFT) is applied. Four parameters are used to quantitatively estimate dynamic changes in the tear film stability of the cornea 20 s after the eye blink. Examples of examined interferograms recorded in patients with healthy eyes, patients suffering from dry-eye syndrome, and patients wearing contact lenses are given. Significant differences between the stability of the tear film in the healthy eye and that in the dry eye and the eye with a contact lens are observed. The favorable influence of artificial tears applied in patients with dry-eye syndrome or contact lenses is also discussed.

Essential Oil of Terminalia chebula Fruits as a Repellent for the Indian Honeybee Apis florea

“…The results indicated that the long-chain fatty acids, i.e., tetradecanoic, palmitic, and oleic acid, did not show any activity. This observation is supported by the fact that although such acids were isolated from pollen grain [20] and propolis [21], an attractant or repellent activity for these acids was not recorded. Similarly, furfural and 5-methylfurfural were also inactive in eliciting any response in honeybees.…”

Optical quality after instillation of eyedrops in dry-eye syndrome

“…Based on results in studies using different methods, such as double-pass, 2,3 retroillumination, 4 aberrometry, [5][6][7][8][9][10][11][12] and interferometry, [13][14][15][16] optical aberrations created by tearfilm breakup contribute to a decline in image quality.…”

Robust estimation of tear film surface quality in lateral shearing interferometry

“…The interference is received by the optical wedge. 9,10 Interferograms present the effect of interference of two subject wavefronts, which are laterally and angularly shifted. Lateral shearing interferometry is one of the most sensitive techniques for recording tear film surface irregularities in a noninvasive manner.…”