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

Bessel beam illumination reduces random and systematic errors in quantitative functional studies using light-sheet microscopy

Light-sheet microscopy (LSM), in combination with intrinsically transparent zebrafish larvae, is a choice method to observe brain function with high frame rates at cellular resolution. Inherently to LSM, however, residual opaque objects cause stripe artifacts, which obscure features of interest and, during functional imaging, modulate fluorescence variations related to neuronal activity. Here, we report how Bessel beams reduce streaking artifacts and produce high-fidelity quantitative data demonstrating a fivefold increase in sensitivity to calcium transients and a 20 fold increase in accuracy in the detection of activity correlations in functional imaging. Furthermore, using principal component analysis, we show that measurements obtained with Bessel beams are clean enough to reveal in one-shot experiments correlations that can not be averaged over trials after stimuli as is the case when studying spontaneous activity. Our results not only demonstrate the contamination of data by systematic and random errors through conventional Gaussian illumination and but,furthermore, quantify the increase in fidelity of such data when using Bessel beams

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

Medidas hiperespectrales de fondo de ojo: una nueva herramienta para el diagnóstico oftalmológico

Peer ReviewedPostprint (published version

Reflectance evaluation of eye fundus structures with a visible and near-infrared multispectral camera

We examined the spectral reflectance of fundus structures in the visible and near-infrared (400–1300 nm) range for contributing to the medical diagnosis of fundus diseases. Spectral images of healthy eye fundus and other ocular diseases were acquired using a novel multispectral fundus camera. Reflectance metrics were computed based on contrast to analyze the spectral features. Significant differences were observed among the structures in healthy and diseased eye fundus. Specifically, near-infrared analysis allows imaging of deeper layers, such as the choroid, which, to date, has not been retrieved using traditional color fundus cameras. Pathological structures, which were hardly observable in color fundus images owing to metamerism, were also revealed by the developed multispectral fundus camera."Funding: H2020Marie Skłodowska-Curie Actions (801342, Tecniospring INDUSTRY); Agència per a la Competitivitat de l’Empresa (801342, Tecniospring INDUSTRY); Generalitat de Catalunya (801342, Tecniospring INDUSTRY); Ministerio de Ciencia e Innovación- Agencia Estatal de Investigación (MCIN/AEI/10.13039/501100011033, PID2020112527RB-I00)"Peer ReviewedPostprint (published version

Análisis colorimétrico de estructuras de fondo de ojo mediante retinografía multiespectral

El análisis del fondo del ojo es crucial para prevenir enfermedades retinianas y coroideas ya que la mayoría no causan síntomas en etapas tempranas. Tratarlas cuando aparecen los primeros indicios es fundamental para evitar pérdidas de visión irreversibles. Con este propósito, el color de las estructuras de fondo de ojo de pacientes sanos y enfermos se evaluó a partir de imágenes adquiridas con una cámara de fondo de ojo multiespectral (400nm-1300nm) con elevada resolución espectral y espacial. En ojos sanos aparecieron diferencias de color CIEDE2000 considerables entre arterias y venas por su diferente oxigenación; las fibras nerviosas y la fóvea aparecieron más contrastadas respecto al fondo, produciendo diferencias de color relevantes. En ojos afectados por degeneración macular asociada a la edad, se pudieron identificar mejor que en retinografías en color las características drusas y alteraciones del disco óptico en pacientes con glaucoma mostraron valores CIEDE2000 elevados respecto a pacientes sanosEste proyecto ha recibido financiación del programa de investigación e innovación Horizon 2020 de la Unión Europea bajo el acuerdo de subvención Marie Skłodowska-Curie No. 801342 (Tecniospring INDUSTRY), así como de la Agència per a la Competitivitat de l’Empresa de la Generalitat de Catalunya (ACCIÓ). Además, esta publicación es parte del proyecto de I+D+i PID2020-112527RB-I00, financiada por MCIN/AEI/10.13039/501100011033.Peer ReviewedPostprint (published version

Análisis colorimétrico de estructuras de fondo de ojo mediante retinografía multiespectral

El análisis del fondo del ojo es crucial para prevenir enfermedades retinianas y coroideas ya que la mayoría no causan síntomas en etapas tempranas. Tratarlas cuando aparecen los primeros indicios es fundamental para evitar pérdidas de visión irreversibles. Con este propósito, el color de las estructuras de fondo de ojo de pacientes sanos y enfermos se evaluó a partir de imágenes adquiridas con una cámara de fondo de ojo multiespectral (400nm-1300nm) con elevada resolución espectral y espacial. En ojos sanos aparecieron diferencias de color CIEDE2000 considerables entre arterias y venas por su diferente oxigenación; las fibras nerviosas y la fóvea aparecieron más contrastadas respecto al fondo, produciendo diferencias de color relevantes. En ojos afectados por degeneración macular asociada a la edad, se pudieron identificar mejor que en retinografías en color las características drusas y alteraciones del disco óptico en pacientes con glaucoma mostraron valores CIEDE2000 elevados respecto a pacientes sanos.Este proyecto ha recibido financiación del programa de investigación e innovación Horizon 2020 de la Unión Europea bajo el acuerdo de subvención Marie kłodowska-Curie No. 801342 (Tecniospring INDUSTRY), así como de la Agència per a la Competitivitat de l’Empresa de la Generalitat de Catalunya (ACCIÓ). Además, esta publicación es parte del proyecto de I+D+i PID2020- 112527RB-I00, financiada por MCIN/AEI/10.13039/501100011033

Bessel Beam Illumination Reduces Random and Systematic Errors in Quantitative Functional Studies Using Light-Sheet Microscopy

Light-sheet microscopy (LSM), in combination with intrinsically transparent zebrafish larvae, is a method of choice to observe brain function with high frame rates at cellular resolution. Inherently to LSM, however, residual opaque objects cause stripe artifacts, which obscure features of interest and, during functional imaging, modulate fluorescence variations related to neuronal activity. Here, we report how Bessel beams reduce streaking artifacts and produce high-fidelity quantitative data demonstrating a fivefold increase in sensitivity to calcium transients and a 20-fold increase in accuracy in the detection of activity correlations in functional imaging. Furthermore, using principal component analysis, we show that measurements obtained with Bessel beams are clean enough to reveal in one-shot experiments correlations that can not be averaged over trials after stimuli as is the case when studying spontaneous activity. Our results not only demonstrate the contamination of data by systematic and random errors through conventional Gaussian illumination and but,furthermore, quantify the increase in fidelity of such data when using Bessel beams

Hyperspectral imaging system for the fast recording of the ocular fundus

Vision loss affects physical, psychological, and emotional wellbeing and social life as well. High life expectancy and health policies are translated into an aging population worldwide, which has higher risk of eye’s disorders and diseases. Therefore, new systems able to contribute at non-invasive objective diagnosis of ocular diseases are demanded. In this context, optical imaging techniques have a primary role as they allow obtaining information from almost any part of the eye. In particular, many important eye and systemic diseases early manifest themselves in the retina and, since the pioneer study of Helmholtz, many resources have been spent to acquire good images of the ocular fundus. In common clinics, fundus photography is restricted to color imaging sensors with only three spectral bands, and, due to metamerism, many structures might remain hidden. Recently, hyperspectral imaging techniques have come to view as a promising and powerful tool for the spectral analysis of several retinal diseases, increasing the amount of information extractable from fundus photography. However, in the literature, examples are restricted to the visible range of the electromagnetic spectrum, have few bands and/or make use of modified commercial fundus cameras. Accordingly, the goal of this project is to build a novel hyperspectral fundus camera based on light-emitting diodes allowing the fast imaging of the retina both in the visible and in the near infrared region of the spectrum, which has never been explored, through a considerable number of spectral bands. This fundus camera has been designed, tested and developed with new custom-made illumination and detection strategies combined with novel cutting- edge technology at the Center for Sensors, Instruments and Systems Development (CD6) of the Universitat Politècnica de Catalunya (UPC, Terrassa). Finally, after a scrupulous clinical study carried out at the Instituto de Microcirugía Ocular (IMO, Barcelona) and at the University Vision Center of UPC (CUV-UPC, Terrassa), qualitative and quantitative results are presented for healthy and diseased eyes. The available spectroscopic information and the visualization of retinal structures and lesions, especially those affecting the choroidal vasculature and retinal pigment epithelium that are hardly visible in conventional color fundus images, underline the clinical potential of this system as a new tool for ophthalmic diagnosis.La pèrdua de visió afecta el benestar físic, psicològic i emocional, i també la vida social de les persones. La llarga esperança de vida i les polítiques de salut es tradueixen en un envelliment de la població a tot el món, la qual presenta un major risc de patir trastorns i malalties oculars. Per tant, es requereixen nous sistemes capaços de contribuir al diagnòstic objectiu no invasiu d'aquestes malalties. En aquest context, les tècniques d’imatge òptica tenen un paper primordial, ja que permeten obtenir informació de gairebé qualsevol part de l’ull. En particular, moltes malalties oculars i sistèmiques importants es manifesten primerencament a la retina i, des de l’estudi pioner de Helmholtz, s’han gastat molts recursos per adquirir bones imatges del fons ocular. Tradicionalment, a les clíniques oftalmològiques, la fotografia de fons d'ull es fa amb sensors d'imatge en color amb només tres bandes espectrals i, a causa del metamerisme, algunes estructures poden romandre amagades. Recentment, les tècniques d’imatge hiperspectral s’han mostrat com una eina prometedora per a l’anàlisi espectral de la retina, augmentant la quantitat d’informació que es pot extreure de la fotografia del fons d'ull. Tanmateix, a la literatura, els exemples es restringeixen al rang visible de l’espectre electromagnètic, tenen poques bandes i/o fan ús de càmeres de fons d'ull comercials modificades. En conseqüència, l’objectiu d’aquest projecte és construir una nova càmera de fons d'ull hiperspectral basada en díodes emissors de llum que permetin obtenir una imatge ràpida de la retina tant a la regió visible com a la de l’infraroig proper de l’espectre, que mai no s’ha explorat, a través d’un nombre considerable de bandes espectrals. Aquesta càmera de fons d'ull ha estat dissenyada i desenvolupada amb noves estratègies d’il·luminació i detecció fetes a mida i combinades amb nova tecnologia d’avantguarda al Centre de Desenvolupament de Sensors, Instrumentació i Sistemes (CD6) de la Universitat Politècnica de Catalunya (UPC, Terrassa). Finalment, després de la realització d’un estudi clínic detallat portat a terme a l’Institut de Microcirurgia Ocular (IMO, Barcelona) i al Centre Universitari de la Visió de la UPC (CUV-UPC, Terrassa), en aquesta tesi es presenten resultats qualitatius i quantitatius tant per a ulls sans com amb malalties de retina. La informació espectroscòpica i la visualització d’estructures i lesions de la retina, especialment aquelles que afecten la vasculatura de coroides i a l’epiteli pigmentari de la retina que són difícilment visibles en les imatges convencionals del fons d'ull en color, posen de manifest el potencial clínic d’aquest sistema com a nova eina per al diagnòstic oftalmològicPostprint (published version