Suchergebnisse

6 pags., 8 figs., 1 tab. -- 2020 IEEE 22nd International Workshop on Multimedia Signal Processing (MMSP), Tampere, Finland, 21-24 Sept. 2020 ; Feature adjustment, understood as the process aimed at modifying at will global features of given signals, has cardinal importance for several signal processing applications, such as enhancement, restoration, style transfer, and synthesis. Despite of this, it has not yet been approached from a general, theory-grounded, perspective. This work proposes a new conceptual and practical methodology that we term Controlled Feature Adjustment (CFA). CFA provides methods for, given a set of parametric global features (scalar functions of discrete signals), (1) constructing a related set of deterministically decoupled features, and (2) adjusting these new features in a controlled way, i.e., each one independently of the others. We illustrate the application of CFA by devising a spectrally-based hierarchically decoupled feature set and applying it to obtain different types of image synthesis that are not achievable using traditional (coupled) feature sets. ; Funded by the Spanish Government grant FIS2016-75891-P

17 pags., 10 figs., tab. -- OCIS codes: (180.4315) Nonlinear microscopy; (170.6900) Three-dimensional microscopy; (170.6935) Tissue characterization; (170.3880) Medical and biological imaging; (100.2960) Image analysis. ; Many optical and biomechanical properties of the cornea, specifically the transparency of the stroma and its stiffness, can be traced to the degree of order and direction of the constituent collagen fibers. To measure the degree of order inside the cornea, a new metric, the order coefficient, was introduced to quantify the organization of the collagen fibers from images of the stroma produced with a custom-developed second harmonic generation microscope. The order coefficient method gave a quantitative assessment of the differences in stromal collagen arrangement across the cornea depths and between untreated stroma and cross-linked stroma. ; European Research Council Advanced Grant (2011-AdG-294099) and Spanish Government (FIS2014-56643). ; Peer Reviewed

1 pag. -- This is a 2020 ARVO Annual Meeting abstract. ; Support COFUND Multiply: European Research Council (ERC) under European Union's Horizon 2020 research and innovation programme H2020-MSCA-COFUND-2015-FP-713694; Spanish government grant FIS2017-84753-R ; Peer reviewed

16 pags., 7 figs. -- OCIS codes: (110.4500) Optical coherence tomography; (110.6880) Three-dimensional image acquisition; (330.7322) Visual optics, accommodation; (100.2960) Image analysis; (330.7327) Visual optics, ophthalmic instrumentation ; The full shape of the accommodating crystalline lens was estimated using custom three-dimensional (3-D) spectral OCT and image processing algorithms. Automatic segmentation and distortion correction were used to construct 3-D models of the lens region visible through the pupil. The lens peripheral region was estimated with a trained and validated parametric model. Nineteen young eyes were measured at 0-6 D accommodative demands in 1.5 D steps. Lens volume, surface area, diameter, and equatorial plane position were automatically quantified. Lens diameter & surface area correlated negatively and equatorial plane position positively with accommodation response. Lens volume remained constant and surface area decreased with accommodation, indicating that the lens material is incompressible and the capsular bag elastic. ; European Research Council under the European Union's Seventh Framework Program (FP/2007-2013) / ERC Grant Agreement (ERC-2011-AdG- 294099); Spanish Government (FIS2011-25637); Spanish Government (FIS2014-56643-R). ; Peer Reviewed

11 pags., 5 figs., 4 tabs. -- Open Access funded by Creative Commons Atribution Licence 4.0 ; In a cataract surgery, the opacified crystalline lens is replaced by an artificial intraocular lens (IOL). To optimize the visual quality after surgery, the intraocular lens to be implanted must be selected preoperatively for every individual patient. Different generations of formulas have been proposed for selecting the intraocular lens dioptric power as a function of its estimated postoperative position. However, very few formulas include crystalline lens information, in most cases only one-dimensional. The present study proposes a new formula to preoperatively estimate the postoperative IOL position (ELP) based on information of the 3-dimensional full shape of the crystalline lens, obtained from quantitative eye anterior segment optical coherence tomography imaging. Real patients were measured before and after cataract surgery (IOL implantation). The IOL position and the postoperative refraction estimation errors were calculated by subtracting the preoperative estimations from the actual values measured after surgery. The proposed ELP formula produced lower estimation errors for both parameters-ELP and refraction-than the predictions obtained with standard state-of-the-art methods, and opens new avenues to the development of new generation IOL power calculation formulas that improve refractive and visual outcomes. ; The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC Grant Agreement ERC-2011-AdG- 294099. This study has been also supported by Spanish government grants FIS2011-25637 and FIS2014-56643-R to S. Marcos. The funding organizations had no role in the design or conduct of this research. ; Peer Reviewed

Producción Científica ; Purpose: Photoactivated cornea collagen cross-linking (CXL) increases corneal stiffness by initiating formation of covalent bonds between stromal proteins. Because CXL depends on diffusion to distribute the photoinitiator, a gradient of CXL efficiency with depth is expected that may affect the degree of stromal collagen organization. We used second harmonic generation (SHG) microscopy to investigate the differences in stromal collagen organization in rabbit eyes after corneal CXL in vivo as a function of depth and time after surgery. Methods: Rabbit corneas were treated in vivo with either riboflavin/UV radiation (UVX) or Rose Bengal/green light (RGX) and evaluated 1 and 2 months after CXL. Collagen fibers were imaged with a custom-built SHG scanning microscope through the central cornea (350 µm depth, 225 × 225 µm en face images). The order coefficient (OC), a metric for collagen organization, and total SHG signal were computed for each depth and compared between treatments. Results: OC values of CXL-treated corneas were larger than untreated corneas by 27% and 20% after 1 month and 38% and 33% after 2 months for the RGX and UVX, respectively. RGX OC values were larger than UVX OC values by 3% and 5% at 1 and 2 months. The SHG signal was higher in CXL corneas than untreated corneas, both at 1 and 2 months after surgery, by 18% and 26% and 1% and 10% for RGX and UVX, respectively. Conclusions: Increased OC corresponded with increased collagen fiber organization in CXL corneas. Changes in collagen organization parallel reported temporal changes in cornea stiffness after CXL and also, surprisingly, are detected deeper in the stroma than the regions stiffened by collagen cross-links. ; European Research Council Advanced Grant ERC-2011-AdG Ref. 294099, Spanish Government Grants FIS2014-56643 and FIS2017-84753-R, H2020 Research and Innovation Action H2020-ICT-2017 Ref. 779960.

12 pags., 6 figs., 3 tabs. -- OCIS codes: (110.4500) Optical coherence tomography, (110.6880) Three-dimensional image acquisition, (100.2960) Image analysis, (330.7327) Visual optics, ophthalmic instrumentation, (330.7324) Visual optics, comparative animal models, (330.5370) Physiological optics ; Custom Spectral Optical Coherence Tomography (SOCT) provided with automatic quantification and distortion correction algorithms was used to measure the 3-D morphology in guinea pig eyes (n = 8, 30 days; n = 5, 40 days). Animals were measured awake in vivo under cyclopegia. Measurements showed low intraocular variability (<4% in corneal and anterior lens radii and <8% in the posterior lens radii, <1% interocular distances). The repeatability of the surface elevation was less than 2 µm. Surface astigmatism was the individual dominant term in all surfaces. Higher-order RMS surface elevation was largest in the posterior lens. Individual surface elevation Zernike terms correlated significantly across corneal and anterior lens surfaces. Higher-order-aberrations (except spherical aberration) were comparable with those predicted by OCT-based eye models. ; European Research Council under the European Union´s Seventh Framework Program (FP/2007-2013;) / ERC Grant Agreement [ERC-2011-AdC-294099], and Spanish Government grant FIS2011-25637; and FIS2014-56643-R to SM. ; Peer Reviewed

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019 ; Support European Research Council (ERC) under European Union's Horizon 2020 research and innovation programme H2020-MSCA-COFUND-2015-FP-713694, Spanish government grant FIS2014-56643-R, European Research Council under the European Union's Seventh Framework programme ERC-2011-AdG-294099, Patent P201130685, Patent US2016 62/329,392. ; Peer reviewed

12 pags., 5+3 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0 ; PURPOSE: Standard evaluation of aberrations from wavefront slope measurements in patients implanted with a rotationally asymmetric multifocal intraocular lens (IOL), the Lentis Mplus (Oculentis GmbH, Berlin, Germany), results in large magnitude primary vertical coma, which is attributed to the intrinsic IOL design. The new proposed method analyzes aberrometry data, allowing disentangling the IOL power pupillary distribution from the true higher order aberrations of the eye. METHODS: The new method of wavefront reconstruction uses retinal spots obtained at both the near and far foci. The method was tested using ray tracing optical simulations in a computer eye model virtually implanted with the Lentis Mplus IOL, with a generic cornea or with anterior segment geometry obtained from custom quantitative spectral-domain optical coherence tomography in a real patient. The method was applied to laser ray tracing aberrometry data at near and far fixation obtained in a patient implanted with the Lentis Mplus IOL. RESULTS: Higher order aberrations evaluated from simulated and real retinal spot diagrams following the new reconstruction approach matched the nominal aberrations (approximately 98%). Previously reported primary vertical coma in patients implanted with this IOL lost significance with the application of the proposed reconstruction. CONCLUSIONS: Custom analysis of ray tracing-based retinal spot diagrams allowed decoupling of the true higher order aberrations of the patient's eye from the power pupillary distribution of a rotationally asymmetric multifocal IOL, therefore providing the appropriate phase map to accurately evaluate through-focus optical quality. ; Supported by Consejería de Educación, Juventud y Deporte of Comunidad de Madrid and the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement no. 291820 to VA; ERC Grant Agreement [ERC-2011-AdG 294099] and Spanish Government Grants FIS2011-25637 and FIS2014-56643-R to SM. ; Peer Reviewed

8 pags., 6 figs. ; Purpose: The crystalline lens undergoes morphological and functional changes with age and may also play a role in eye emmetropisation. Both the geometry and the gradient index of refraction (GRIN) distribution contribute to the lens optical properties. We studied the lens GRIN in the guinea pig, a common animal model to study myopia. Methods: Lenses were extracted from guinea pigs (Cavia porcellus) at 18 days of age (n = 4, three monolaterally treated with negative lenses and one untreated) and 39 days of age (n = 4, all untreated). Treated eyes were myopic (−2.07 D on average) and untreated eyes hyperopic (+3.3 D), as revealed using streak retinoscopy in the live and cyclopeged animals. A custom 3D spectral domain optical coherence tomography (OCT) system (λ = 840 nm, Δλ = 50 nm) was used to image the enucleated crystalline lens at two orientations. Custom algorithms were used to estimate the lens shape and GRIN was modelled with four variables that were reconstructed using the OCT data and a minimisation algorithm. Ray tracing was used to calculate the optical power and spherical aberration assuming a homogeneous refractive index or the estimated GRIN. Results: Guinea pig lenses exhibited nearly parabolic GRIN profiles. When comparing the two age groups (18- and 39 day-old) there was a significant increase in the central thickness (from 3.61 to 3.74 mm), and in the refractive index of the surface (from 1.362 to 1.366) and the nucleus (from 1.443 to 1.454). The presence of GRIN shifted the spherical aberration (−4.1 µm on average) of the lens towards negative values. Conclusions: The guinea pig lens exhibits a GRIN profile with surface and nucleus refractive indices that increase slightly during the first days of life. GRIN plays a major role in the lens optical properties and should be incorporated into computational guinea pig eye models to study emmetropisation, myopia development and ageing. ; This work was supported by European Research Council (ERC) Grant Agreement ERC-2011-AdC- 294099; ERC under the European Union's Horizon 2020 research and innovation programme (H2020-MSCA COFUND-2015 FP-713694, MULTIPLY) and under grant agreement No 779960, IMCUSTOMEYE and No 675137 (MyFUun MSCA ITN); Spanish Government Grant FIS2017-84753-R; Hunter Medical Research Institute G1400967 and the University of Newcastle (FVG 1031537 and SSP).

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019. ; Support Spanish Government Grant FIS2014-56643-R; Spanish Government Grant FIS2017-84753-R; European Project Presbyopia ERC-2011-AdG Ref. 294099; National Eye Institute Grants 2R01EY021834, P30EY14801 (Center Grant); the Hyderabad Eye Research Foundation; Florida Lions Eye Bank and the Beauty of Sight Foundation; Drs KR Olsen and ME Hildebrandt; Drs R Urs and A Furtado; the Henri and Flore Lesieur Foundation (JMP); an unrestricted grant from Research to Prevent Blindness. ; Peer reviewed

6 pags., 2 figs., 2 tabs. ; There have been many studies on lens properties in specific populations (e.g. in China, Europe, Singapore, etc.) some of which suggest there may be differences between populations. Differences could be caused by ethnic or environmental influences or experimental procedures. The purpose of this study is to evaluate if any differences exist between Indian and European populations in the central geometric and full shape properties of human lenses. Two custom-developed spectral domain optical coherence tomography systems were used to acquire the crystalline lens geometry: one in India (69 lenses from 59 donors) and the other in Spain (24 lenses from 19 donors). The steps for obtaining accurate 3-D models from optical coherence tomography raw images comprised of image segmentation, fan and optical distortion correction, tilt removal and registration. The outcome variables were lens equatorial diameter, lens thickness, anterior and posterior lens thicknesses and their ratio, central radius of curvature of the anterior and posterior lens surfaces, lens volume and lens surface area. A mixed effects model by maximum likelihood estimation was used to evaluate the effect of age, population and their interaction (age*population) on lens parameters. After adjusting for age, there were no population differences observed in anterior and posterior radii of curvature, equatorial diameter, lens thickness, anterior and posterior lens thicknesses and their ratio, volume and surface area (all p ≥ 0.08). There was also no effect of the interaction term on anterior and posterior radii of curvature, equatorial diameter, lens thickness, anterior and posterior lens thicknesses and their ratio, volume and surface area (all p ≥ 0.06). All central geometric and full shape parameters appeared to be comparable between the European and Indian populations. This is the first study to compare geometric and full shape lens parameters between different populations in vitro. ; This work was supported by the National Institutes of Health/National Eye Institute [Grants 2R01EY021834 and P30EY14801 (Center Grant)]; the Hyderabad Eye Research Foundation; Ministerio de Educacion y Ciencia, Spain (FIS2017- 84753-R), European Research Council (ERC-2018-AdG-833106) and IMCUSTOMEYE Ref. 779960 (H2020- ICT- 2017-1) to S. Marcos, and European Research Council (ERC) under European Union's Horizon 2020 research and innovation programme H2020-MSCA COFUND-2015 FP-713694, MULTIPLY(AdC), CSIC ICoop Program, Florida Lions Eye Bank and the Beauty of Sight Foundation, an unrestricted grant from Research to Prevent Blindness to the Department of Ophthalmology, University of Miami and the Henri and Flore Lesieur Foundation (J-M. Parel).

ARVO Annual Meeting Abstract ; Support European Project COFUND Multiply H-2020-MSCA-COFUND-2015 Ref. 713694; European Project IMCUSTOMEYE H2020-ICT-2017 Ref. 779960; European Project MyFUN H2020-MSCA-ITN-2015 Ref. 675137; Spanish government grant FIS2017-84753-R ; Peer reviewed

1 pag. -- This is a 2020 ARVO Annual Meeting abstract. ; Support European Project COFUND Multiply H-2020-MSCA-COFUND-2015 Ref. 713694; European Project IMCUSTOMEYE H2020-ICT-2017 Ref. 779960; European Project MyFUN H2020-MSCA-ITN-2015 Ref. 675137; Spanish government grant FIS2017-84753-R ; Peer reviewed

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019 ; Support European Research Council ERC-2011-AdG-294099; Spanish Government: FIS2017-84753-R, PTQ-15-07432, and ISCIII DTS16/00127; Spanish Goverment predoctoral program FPU16/01944; Collaborative agreement with Johnson & Johnson Vision, Inc., Jacksonville, FL, USA ; Peer reviewed