Epithelial and stromal remodelling following femtosecond laser–assisted stromal lenticule addition keratoplasty (SLAK) for keratoconus

The purpose of this study was to evaluate corneal epithelium and stromal remodelling with anterior segment optical coherence tomography in patients who have undergone stromal lenticule addition keratoplasty (SLAK) for advanced keratoconus. This was a prospective non-comparative observational study. Fifteen eyes of 15 patients with advanced keratoconus underwent implantation with a cadaveric, donor negative meniscus-shaped intrastromal lenticule, produced with a femtosecond laser, into a stromal pocket dissected in the recipient cornea at a depth of 120 μm. Simulated keratometry, central corneal thickness (CTT), corneal thinnest point (CTP), central epithelial thickness (CET), central and peripheral lenticule thickness, anterior and posterior stromal thickness were measured. Regional central corneal epithelial thickness (CET) and variations in the inner annular area (IAT) and outer annular area (OAT) were also analysed. All parameters were measured preoperatively and 1, 3, and 6 months postoperatively. The average anterior Sim-k decreased from 59.63 ± 7.58 preoperatively to 57.19 ± 6.33 D 6 months postoperatively. CCT, CTP, CET, and OAT increased and IAT decreased significantly after 1 month. All parameters appeared unchanged at 6-months except that of OAT that further increased. Lenticule thickness was stable. In conclusion we observed that SLAK reshapes the cornea by central flattening with stromal thickening and epithelial thickness restoration

In vivo microscopic and optical coherence tomography classification of neurotrophic keratopathy

© 2018 Wiley Periodicals, Inc. Neurotrophic keratopathy (NK) is a rare degenerative corneal disorder characterized by instability of epithelial integrity with consequent epithelial defects that can worsen up to persistent epithelial defects with stromal melting and ulceration. The pathogenesis of NK springs from a variable degree of damage to the trigeminal nerve plexus, leading to a reduction or total loss of corneal sensitivity. Mackie classification (1995) distinguishes three stages of NK, based on the severity of clinical presentation. The technological innovations in corneal diagnostic imaging allow clinicians to accurately study the morphometry and morphology of corneal structure with microscopic resolution. In this study, 45 patients affected by NK at different stages underwent in vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (AS-OCT) with particular attention to analyze subbasal nerve plexus fibers and the stromal structure. At the light of IVCM and AS-OCT observations, we propose a different staging of NK with respect to the Mackie's classification that takes into account the severity of subbasal nerve fibers damage and the extension in depth of stromal ulceration; this classification better defines, at the time of diagnosis, the cellular and structural alterations in the affected corneas, with possible prognostic and therapeutic values in the management of NK

Photochemical colour changes on chestnut wood surface

The aim of this work is to study the surface colour and chemical modifications in chestnut wood samples as a consequence of irradiating in a controlled environment. The changes were investigated by reflectance spectrophotometry in a totally non-invasive modality, and further deepened by Fourier transform infrared spectroscopy and hyperspectral imaging, in order to obtain forecast models to describe the phenomenon. The statistical elaboration of the data allowed to validate the measurements and to obtain models enabling to relate the investigated parameters; the elaboration of the hyperspectral images by chemometric methods allowed to study the changes in the spectra. A result of great importance is the possibility to correlate the lignin alteration with the colour changes. This result is relevant in the field of cultural heritage and in general in the control processes of wooden materials

Opaque bubble layer incidence in Femtosecond laser-assisted LASIK: comparison among different flap design parameters

The purpose of this study was to evaluate the incidence of opaque bubble layer (OBL) in femtosecond laser-assisted in situ keratomileusis (LASIK) flaps created with the support of Visumax Carl Zeiss femtosecond laser, planned with different flap diameters (7.90, 8.0, and 8.20 mm) and the same laser energy and power settings. Incidence of intraoperative OBL in flaps of consecutive 108 patients (216 eyes) subjected to bilateral femtosecond-assisted LASIK was considered. Flap creation was performed with the same laser design parameters (spot distance and energy offset) and different presetting diameters of 7.90 mm (72 eyes, group 1), 8 mm (72 eyes, group 2), and 8.20 mm (72 eyes, group 3). The incidence of OBL was considered and its extension was reported measuring involvement of different four corneal flap quadrants in which was theoretically divided the entire flap area; based on these data, OBL presence was classified as none (no evidence of OBL), minimal (minimal presence in not more that one quadrants corneal flap), mild (OBL presence in almost two or three quadrants without tendency to invade central cornea), and moderate (OBL presence in almost three quadrants with tendency to invade central cornea). In group 1, the incidence of OBL was of 23.6 % (17 eyes) with a mild/moderate presence; in group 2, incidence was 20.8 % (15 eyes) with mild presence. Group 3 presented a reduced OBL incidence (4.1 %, 3 eye) with a minimal presence. No statistically significant difference was found between group 1 and 2 (p = 0.8414).We found statistically significant differences between group 1 and group 3 (p = 0.0012) and between groups 2 and 3 (p = 0.0044). A significant reduction and extension of OBL incidence were evident when LASIK flap settings diameter was increased, and flap edge was closer to the contact glass border; this is probably consequent to a more effective gas dispersion outside of corneal flap

Protective behaviour monitoring on wood photo-degradation by spectroscopic techniques coupled with chemometrics

This paper reports the investigation on the effect of protective materials on poplar (Populus sp.) wood modifications as consequence of artificial photo-degradation in controlled environment. The novelty of this work is to try to understandwhat happens towood surface under the protective layer. Shellac, beeswax and Linfoil®were tested to compare traditional and novel products generally used for wood. The samples, uncovered and covered by these protective layers,were artificially aged. Colour and chemical modifications due to ageingwere investigated at different time intervals by reflectance spectrophotometry, Fourier transform infrared spectroscopy and hyperspectral imaging. The obtained data were elaborated by statistical and chemometric tools in order to verify their significance and to assess the relationship between groups of measurements. The results highlighted that shellac, beeswax and Linfoil® materials have a very low protective effect on wood photo-degradation for long times of exposure, by little reducing the changes of wood components

Hyperspectral imaging as a technique for investigating the effect of consolidating materials on wood

The focus of this study was to investigate the potential of hyperspectral imaging (HSI) in the monitoring of commercial consolidant products applied on wood samples. Poplar (Populus spp.) and walnut (Juglans Regia L.) were chosen for the consolidant application. Both traditional and innovative products were selected, based on acrylic, epoxy, and aliphatic compounds. Wood samples were stressed by freeze/thaw cycles in order to cause material degradation without the loss of wood components. Then the consolidant was applied under vacuum. The samples were finally artificially aged for 168 h in a solar box chamber. The samples were acquired in the short wave infrared (1000 to 2500 nm) range by SISUChema XL™device (Specim, Finland) after 168 h of irradiation. As comparison, color measurement was also used as an economic, simple, and noninvasive technique to evaluate the deterioration and consolidation effects on wood. All data were then processed adopting a chemometric approach finalized to define correlation models, HSI based, between consolidating materials, wood species, and short-time aging effects