Transparency of ocular structures is an important factor determining contrast in the retinal image. Although opacities are most commonly formed in the crystalline lens of aging eye (cataract formation), visual function can be also altered by the opacities in the vitreous body. Therefore, macro- and micro-scale visualization of vitreous is clinically relevant since alterations of vitreous organization impact retinal diseases and affect vision. However, optical imaging of the vitreous body is challenging due to its transparency. We demonstrate visualization of vitreous and its opacities in vivo using optical coherence tomography (OCT). We developed a prototype long-depth-range Swept-Source OCT instrument operating at the speed of 30 kA-scans/second and at the central wavelength of 1 μm to perform high-resolution imaging through the entire vitreous depth. The interface with focus-tunable optics has been used to optimize the field of view. 2-D and 3-D OCT data sets of eyes with vitreous opacities were acquired and processed to obtain contrast-enhanced high-resolution images of vitreous. The results demonstrate the ability of the OCT imaging to characterize the opacities that cause floaters. In conclusion, long-depth-range SS-OCT enables volumetric visualization of in vivo microstructural changes in the vitreous body. This instrument might be a useful tool in high-resolution evaluation and surgical management of vitreous opacities.
Optical methods have been recently used to perform objective assessment of crystalline lens and corneal opacities. Swept-source optical coherence tomography (SS-OCT) enables measurements of the back-reflected or back-scattered photons from the internal objects. In this work, we present a long-depth range SS-OCT system, with a focus tunable lens, optimized for the visualization of large sections of the posterior segment of the eye, including the vitreous. The system was validated using an eye model.
Three devices based on tapered optical fibres are used to determine the presence of pollutants in water, through the measure of their spectral transmittance. Tapered optical silica fibres, coated (or not) with metallic and dielectric layers (Al or Cu and TiO2) are employed. It is found that, with our experimental arrangement, the presence of products derived from gasoline spills can be determined when we use the coated tapers. A complete characterization of the three different tapers is made in a wide spectral range (1300-1650 nm) and the wavelengths most suitable to detect and discern the hydrocarbons measured are identified. The results obtained show that these devices can be used for the early detection of oil spills in seawater in an industrial environment as simple and versatile sensors that can be self-cleaned with the movement of seawater.