Quality of vision: beyond the fields of ophthalmology and optics

Postprint (published version

Terahertz-based system for dehydration analysis of hydrogel contact lenses

The use of terahertz-based techniques has grown very fast since they are capable of performingevaluations at molecular level, being very suitable for the analysis of biological samples and bioma-terials such as those for contact lenses. These biomaterials are continuously evolving to enhancethe lens wearer’s comfort by improving their hydration state and surface wettability. Therefore, thisstudy examines a novel terahertz system for the assessment of the temporary in vitro dehydrationof hydrogel contact lenses, which provides a new index to assess their state of hydration. Severalconventional and silicone hydrogel contact lenses and lens care solutions were analysed. Traditionalmethods such as the gravimetric determination of water content and the measurement of the staticcontact angle were also carried out for the validation of the developed system. The dehydrationrate measurements of contact lenses obtained with the proposed system correlated with the valuesprovided by traditional methods. As a whole, conventional hydrogel contact lenses exhibited thelowest values for dehydration rate. The tests conducted on various solutions showed a correlationbetween the wetting action of the solution and the dehydration rate of the contact lens material.Peer ReviewedPostprint (published version

Incoherent Light Sources for Speckle Reduction in Double Pass Ocular Imaging

Postprint (published version

Experimental characterization of the speckle pattern at the output of a multimode optical fiber

Speckle patterns produced by coherent waves interfering with each other are undesirable in many imaging applications (for example, in laser projection systems) but on the other hand, they contain useful information that can be exploited (for example, for blood flow analysis or reconstruction of the object that generates the speckle). It is therefore important to understand how speckle can be enhanced or reduced by tailoring the coherence of laser light. Using a conventional semiconductor laser and a multimode optical fiber we study experimentally how the speckle pattern depends on the laser pump current and on the image acquisition settings. By varying the pump current from below to above the lasing threshold, and simultaneously tuning the image exposure time to compensate for the change in brightness, we find conditions that allow for recorded images with similar average intensity, but with speckle contrast (the standard deviation of the intensity over the average intensity) as low as 0.16, or as high as 0.99.Peer ReviewedPostprint (published version

Colorimetric analysis of eye fundus structures with multispectral retinography

The analysis of the eye fundus is critical to prevent retinal and choroidal diseases since most of them cause no symptoms at early stages. Treating them when the very first signs appear is crucial to avoid vision losses. To this end, the color of eye fundus structures of healthy and diseased patients was assessed from images acquired with a novel multispectral fundus camera (400 nm – 1300 nm) with high spectral and spatial resolution. Characteristic color traits were found: in healthy eyes, large CIEDE2000 color differences were reported between arteries and veins due to different blood oxygenation; the contrast of nerve fibers/fovea was enhanced, giving rise to relevant color differences; in eyes with age related macular degeneration, lesions such as drusen could be better distinguished than with traditional color retinography; alterations of the optic disk in patients with glaucoma were also assessed, showing remarkable CIEDE2000 values when compared to healthy patientsThis project has received funding from the European Union's Horizon 2020 research and innovation programme under Marie Skłodowska-Curie grant agreement No. 801342 (Tecniospring INDUSTRY) and the Government of Catalonia's Agency for Business Competitiveness (ACCIÓ). This research was also supported by the Ministerio de Economía, Industria y Competitividad (MINECO), the Agencia Estatal de Investigación (AEI) and the European Regional Development Fund (FEDER) under the grant DPI2017-89414-R.Peer ReviewedPostprint (published version

Speckle reduction in double-pass retinal images

Postprint (published version

Handheld 3D scanning system for in-vivo imaging of skin cancer

Postprint (published version

Fast visible and extended nearinfrared multispectral fundus camera

We present a multispectral fundus camera that performs fast imaging of the ocular posterior pole in the visible and near-infrared (400 to 1300 nm) wavelengths through 15 spectral bands, using a flashlight source made of light-emitting diodes, and CMOS and InGaAs cameras. We investigate the potential of this system for visualizing occult and overlapping structures of the retina in the unexplored wavelength range beyond 900 nm, in which radiation can penetrate deeper into the tissue. Reflectance values at each pixel are also retrieved from the acquired images in the analyzed spectral range. The available spectroscopic information and the visualization of retinal structures, specifically the choroidal vasculature and drusen-induced retinal pigment epithelium degeneration, which are hardly visible in conventional color fundus images, underline the clinical potential of this system as a new tool for ophthalmic diagnosis.Peer ReviewedPostprint (published version

Task oriented visual satisfaction and wearing success with two different simultaneous vision multifocal soft contact lenses

Postprint (published version

Texture Evaluation of Automotive Coatings by Means of a Gonio-Hyperspectral Imaging System Based on Light-Emitting Diodes

Sparkle and graininess are textural effects that appear as intrinsic spatial features of coatings containing goniochromatic pigments, whereas others such as mottling are undesired outcomes. In this study, we present new methods for the evaluation of sparkle, graininess and mottling of automotive coatings through images acquired with a novel gonio-hyperspectral imaging system based on light-emitting diodes with extended spectral sensitivity beyond the visible range (368–1309 nm). A novel analysis of sparkle that considered the amount of sparkling spots was used. Graininess was quantified through a novel statistical descriptor based on the energy descriptor computed from the histogram. A new index was proposed for an enhanced detection of mottling based on the analysis of striping, which was better observed and quantified in the infrared range. Spectral assessments showed a strong relationship with color and spectral reflectance for graininess and mottling. In conclusion, the results showed that these new spatial and spectral methods are a suitable, alternative and potential approach for the assessment of these textural features.Ministerio de Ciencia e Innovación (MICINN, DPI2011-30090-C02-01) and Ministerio de Economía y Competitividad (MINECO, DPI2014-56850-R); and the European Union