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Silvia Tavazzi,1,2 Federica Cozza,1,2 Gabriele Nigrotti,2 Chiara Braga,2 Natalia Vlasak,3 Silvano Larcher,4 Fabrizio Zeri1,2,5 1Department of Materials Science, University of Milano Bicocca, Milan, Italy; 2Research Centre in Optics and Optometry (COMiB), University of Milano Bicocca, Milan, Italy; 3Hoya Vision Care, Amsterdam, the Netherlands; 4Hoya Lens Italy, Milan, Italy; 5Ophthalmic Research Group, School of Life and Health Sciences, Aston University, Birmingham, UKCorrespondence: Silvia Tavazzi Email silvia.tavazzi@unimib.itPurpose: The work was aimed at comparing contrast sensitivity performance in an indoor environment with two filters, which differ only in the presence of a band at 450± 20 nm in the transmittance spectrum.Patients and Methods: Thirty-nine subjects participated. The filters were the Standard (ST) and Professional (PRO) Drive lenses (Hoya, Japan), the latter showing the attenuation band at 450 nm. Photopic contrast sensitivity (CS) was measured at different spatial frequencies from 1.5 to 18 cpd through Functional Acuity Contrast Test with both lenses (LogCSST and LogCSPRO, respectively). The areas under the curves of LogCSST and LogCSPRO as a function of the spatial frequency were also considered.Results: In the range of the measured values of LogCSST for the thirty-nine participants, at each spatial frequency and also for the areas, the difference Δ = LogCSPRO – LogCSST was found to decrease and change sign from positive to negative as a function of LogCSST, thus allowing to deduce a threshold (LogCSthreshold) for LogCSST corresponding to Δ=0. Significant CS worsening was found with the PRO compared to the ST lens for the subjects showing LogCSST > LogCSthreshold. Vice versa, CS improvement was found when LogCSST < LogCSthreshold.Conclusion: In the choice of a blue-filtering lens, practitioners should take into consideration that the attenuation of light in the range 420– 470 n

Purpose: For morphometric analysis of the cell mosaic of corneal endothelium, checking accuracy and precision of instrumentation is a key step. In this study, a standard reference sample is proposed, developed to reproduce the cornea with its shape and the endothelium with its intrinsic variability in the cell size. Methods: A polystyrene bead layer (representing the endothelium) was deposited on a lens (representing the cornea). Bead diameters were 20, 25, and 30 m (fractions in number 55%, 30%, and 15%, respectively). Bead density and hexagonality were simulated to obtain the expected true values and measured using a slit-lamp endothelial microscope applied to 1) a Takagi 700GL slit lamp at 40× magnification (recommended standard setup) and 2) a Takagi 2ZL slit lamp at 25× magnification. Results: The simulation provided the expected bead density 2001 mm-2 and hexagonality 47%. At 40×, density and hexagonality were measured to be 2009 mm-2 (SD 93 mm-2) and 45% (SD 3%). At 25× on a different slit lamp, the comparison between measured and expected densities provided the factor 1.526 to resize the image and to use the current algorithms of the slit-lamp endothelial microscope for cell recognition. Conclusions: A variable-size polystyrene bead layer on a lens is proposed as a standard sample mimicking the real shape of the cornea and the variability of cell size and cell arrangement of corneal endothelium. The sample is suggested to evaluate accuracy and precision of cell density and hexagonality obtained by different endothelial microscopes, including a slit-lamp endothelial microscope applied to different slit lamps, also at different magnifications

Purpose: A method called EndoKer was recently devised for the morphometric analysis of the cell mosaic of the corneal endothelium. Fully automatic cell recognition is performed on images acquired by a slit-lamp biomicroscope. The aim of this study was to evaluate the accuracy of the EndoKer results. Methods: Analyses were performed on a polystyrene bead layer stratified on a contact lens and in vivo on 30 adults. Accuracy was evaluated by comparing the results of EndoKer with the true values obtained by manual counting of the cells in the same images. EndoKer results were also compared with those obtained with the Tomey EM3000 microscope. Results: The accuracy of the results compared with the manual counting on the same images showed a difference of a few percent for the cell density and for hexagonality. This high accuracy derives from (1) the resolution of the slit-lamp images and (2) the improved cell recognition of the fully automatic method. A good agreement was also found between EndoKer and the Tomey EM3000 microscope results. Conclusions: Based on the investigated 30 cases, the slit-lamp biomicroscope may be a viable alternative to dedicated endothelial instruments, providing the additional advantages of a larger investigated area and the possibility to take images of different portions of the cornea. The calibration was performed during the development of the method by using polystyrene beads. The user is not required to perform this calibration. However, such a calibrated sample is suggested for those interested.

Molecular arrangement plays a role in the diffusion of water and solutes across soft contact lenses. In particular, the uptake of solutes in hydrated contact lenses can occur as long as free water is available for diffusion. In this work, we investigated the effect of mechanical vibrations of low frequency (200. Hz) on the solute uptake. Hyaluronan, a polysaccharide of ophthalmic use, was taken as example of solute of interest. For a specific water-hydrated hydrogel material, differential scanning calorimetry experiments showed that a large fraction of the hydration water accounted for loosely-bound water, both before and after one week of daily-wear of the lenses. The size (of the order of magnitude of few hundreds of nanometers) of hyaluronan in aqueous solution was found to be less than the size of the pores of the lens observed by scanning electron microscopy. However, solute uptake in already-hydrated lenses was negligible by simple immersion, while a significant increase occurred under mechanical vibrations of 200. Hz, thus providing experimental evidence of mechanically triggered enhanced solute uptake, which is attributed to the release of interfacial loosely-bound water. Also other materials were taken into consideration. However, the effectiveness of mechanical vibrations for hyaluronan uptake is restricted to lenses containing interfacial loosely-bound water. Indeed, loosely-bound water is expected to be bound to the polymer with bonding energies of the order of magnitude of 10-100. J/g, which are compatible with the energy input supplied by the vibrations.

The purpose of this study was a comparison between new and worn siloxane-hydrogel contact lenses in terms of microscopic structure, surface morphology, and loading of hyaluronan. The analyses were performed by scanning electron microscopy, with the support of the freeze-drying technique, and by fluorescence confocal microscopy. Along the depth profile of new lenses, a thin porous top layer was observed, which corresponds to the region of hyaluronan penetration inside well-defined channels. The time evolution was followed from one day to two weeks of daily wear, when a completely different scenario was found. Clear experimental evidence of a buggy surface was observed with several crests and regions of swelling, which could be filled by the hyaluronan solution. The modifications are attributed to the progressive relaxation of the structure of the polymeric network.

Drug-loaded contact lenses are emerging as the preferred treatment method for several ocular diseases, and efforts are being directed to promote extended and controlled delivery. One strategy is based on delivery induced by environmental triggers. One of these triggers can be hydrogen peroxide, since many platforms based on drug-loaded nanoparticles were demonstrated to be hydrogen-peroxide responsive. This is particularly interesting when hydrogen peroxide is the result of a specific pathophysiological condition. Otherwise, an alternative route to induce drug delivery is here proposed, namely the mechano-synthesis. The present work represents the proof-of-concept of the mechanosynthesis of hydrogen peroxide in siloxane-hydrogel contact lenses as a consequence of the cleavage of siloxane bonds at the interface between the polymer and water in aqueous phase. Their spongy morphology makes contact lenses promising systems for mechanical-to-chemical energy conversion, since the amount of hydrogen peroxide is expected to scale with the interfacial area between the polymer and water. The eyelid pressure during wear is sufficient to induce the hydrogen peroxide synthesis with concentrations which are biocompatible and suitable to trigger the drug release through hydrogen-peroxide-responsive platforms. For possible delivery on demand, the integration of piezoelectric polymers in the siloxanehydrogel contact lenses could be designed, whose mechanical deformation could be induced by an applied wireless-controlled voltage. (Figure Presented).