The cell morphology is a valuable indicator of the physical condition and general status of the cell. Here we demonstrate
a methodology for noninvasive biosensing of adherent living cells. Our method is based on infrared reflection
spectroscopy of living cells cultured on thin Au film. To characterize cell morphology we utilized the unique properties
of the infrared surface plasmon (λ=1-3 μm) and infrared guided wave that travel inside the cell monolayer. We
demonstrate that our method enables monitoring of submicron variations in cell morphology in real-time and in a labelfree
manner. In addition to morphological characterization, our method allows investigation of chemical composition
and molecular structure of cells through infrared absorption spectroscopy analysis.
The optical properties of the cornea have been a research subject of great interest for many years. Several
early theories have been put forward to explain with more or less success the optical transparency of this
tissue, but it was not until Maurice demonstrated in a very elegant way during the 50s that this optical
transparency could be explained by the regular ultrastructure of the cornea. When becoming edematous, the
cornea's ultrastructure is perturbed and the tissue becomes a strongly scattering medium.
With the emergence of ophthalmologic surgery by ultrashort pulse lasers in recent years, a regain of interest in
the subject of corneal transparency arose. However, relatively little and no recent data of transparency spectra
measurements covering a large wavelength range is available in the literature. The purpose of this study is to
provide quantitative values for light scattering and its relation to the degree of edema by measuring the
spectrum of transmitted light through corneas presenting different degrees of edema. This paper focus on the
comparison of laboratory measurements published earlier with a new simple method we propose We also for
eye banks to quantitatively measure the degree of transparency of corneal grafts by measuring the modulation
transfer function of a Siemens star viewed through a corneal graft. Indeed, there is no current method to
determine the transparency of corneal graft but the subjectivity of the laboratory technician or the ophthalmic
surgeon.
Femtosecond laser surgery in the volume of corneal tissue is typically performed wavelengths of about 1 μm,
which gives excellent results on transparent corneas. However, the outcome is much worse in the case of
oedematous or pathological corneas as the laser beam propagation is disturbed by optical scattering. Our studies
suggest that this phenomenon can be greatly reduced by using a better suited laser wavelength. Best results are
obtained at 1.65 μm.
Currently, no compact femtosecond laser at this wavelength is commercially available. We have developed a
new simple, compact and stable laser source consisting of a non linear crystal pumped by a compact commercial
solid-state laser emitting at 1.03 μm in a configuration of an Optical Parametric Generation (OPG). The output
wavelength of this system can be tuned in the spectral range of 1.45 - 1.8 μm. A series of ex vivo penetrating
incisions using energies of the order of a few microjoules on corneal tissues have been performed while varying
the wavelengths from 1.45 μm to 1.7 μm. The results have been compared to experiments performed at 0.8 μm
and 1 μm. The use of longer infrared wavelengths around 1.65 μm for femtosecond laser keratoplasty
significantly improves the quality and the penetration depth of incision in case of pathological tissues, without
inducing any additional side effects.
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