1. Articles from Susana Marcos

    1-24 of 27 1 2 »
    1. OCT-based full crystalline lens shape change during accommodation in vivo

      OCT-based full crystalline lens shape change during accommodation in vivo

      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 ...

      Read Full Article
    2. Optical Coherence Tomography Based Estimates of Crystalline Lens Volume, Equatorial Diameter, and Plane Position

      Optical Coherence Tomography Based Estimates of Crystalline Lens Volume, Equatorial Diameter, and Plane Position

      Purpose : Measurement of crystalline lens geometry in vivo is critical to optimize performance of state-of-the-art cataract surgery. We used custom-developed quantitative anterior segment optical coherence tomography (OCT) and developed dedicated algorithms to estimate lens volume (VOL), equatorial diameter (DIA), and equatorial plane position (EPP). Methods : The method was validated ex vivo in 27 human donor (19–71 years of age) lenses, which were imaged in three-dimensions by OCT. In vivo conditions were simulated assuming that only the information within a given pupil size (PS) was available. A parametric model was used to estimate the whole lens shape from PS-limited data ...

      Read Full Article
    3. OCT-based crystalline lens topography in accommodating eyes

      OCT-based crystalline lens topography in accommodating eyes

      ustom Spectral Domain Optical Coherence Tomography (SD-OCT) provided with automatic quantification and distortion correction algorithms was used to measure anterior and posterior crystalline lens surface elevation in accommodating eyes and to evaluate relationships between anterior segment surfaces. Nine young eyes were measured at different accommodative demands. Anterior and posterior lens radii of curvature decreased at a rate of 0.78 ± 0.18 and 0.13 ± 0.07 mm/D, anterior chamber depth decreased at 0.04 ± 0.01 mm/D and lens thickness increased at 0.04 ± 0.01 mm/D with accommodation. Three-dimensional surface elevations were estimated by subtracting ...

      Read Full Article
    4. Observation of sound-induced corneal vibrational modes by optical coherence tomography

      Observation of sound-induced corneal vibrational modes by optical coherence tomography

      The mechanical stability of the cornea is critical for maintaining its normal shape and refractive function. Here, we report an observation of the mechanical resonance modes of the cornea excited by sound waves and detected by using phase-sensitive optical coherence tomography. The cornea in bovine eye globes exhibited three resonance modes in a frequency range of 50-400 Hz. The vibration amplitude of the fundamental mode at 80-120 Hz was ~8 µm at a sound pressure level of 100 dB (2 Pa). Vibrography allows the visualization of the radially symmetric profiles of the resonance modes. A dynamic finite-element analysis supports our ...

      Read Full Article
    5. Numerical model of optical coherence tomographic vibrography imaging to estimate corneal biomechanical properties

      Numerical model of optical coherence tomographic vibrography imaging to estimate corneal biomechanical properties

      Most techniques measuring corneal biomechanics in vivo are biased by side factors. We demonstrate the ability of optical coherence tomographic (OCT) vibrography to determine corneal material parameters, while reducing current prevalent restrictions of other techniques (such as intraocular pressure (IOP) and thickness dependency). Modal analysis was performed in a finite-element (FE) model to study the oscillation response in isolated thin corneal flaps/eye globes and to analyse the dependency of the frequency response function on: corneal elasticity, viscoelasticity, geometry (thickness and curvature), IOP and density. The model was verified experimentally in flaps from three bovine corneas and in two enucleated ...

      Read Full Article
    6. OCT 3-D surface topography of isolated human crystalline lenses

      OCT 3-D surface topography of isolated human crystalline lenses

      Quantitative 3-D Optical Coherence Tomography was used to measure surface topography of 36 isolated human lenses, and to evaluate the relationship between anterior and posterior lens surface shape and their changes with age. All lens surfaces were fitted to 6th order Zernike polynomials. Astigmatism was the predominant surface aberration in anterior and posterior lens surfaces (accounting for ~55% and ~63% of the variance respectively), followed by spherical terms, coma, trefoil and tetrafoil. The amount of anterior and posterior surface astigmatism did not vary significantly with age. The relative angle between anterior and posterior surface astigmatism axes was on average 36 ...

      Read Full Article
    7. Madrid-MIT +Vision Consortium announces Fellowships in Translational Biomedical Imaging

      Madrid-MIT +Vision Consortium announces Fellowships in Translational Biomedical Imaging

      Madrid-MIT +Vision Consortium announces Fellowships in Translational Biomedical Imaging. Fellowships entail a training program in Madrid and Boston and development of collaborative projects between institutions in both cities. The Institute of Optics-CSIC (Madrid), as a member of the Consortium, encourages postdoctoral applications in the fields of optical ocular imaging within the frame of this program. Application deadline: April 30th 2014. Starting date: September 2th 2014. Full announcement: http://viobiolabs.wordpress.com/2014/03/14/2014-mvision-fellowship-call-for-applications/ More information on the Fellowship program: http://mvisionconsortium.mit.edu/fellowship Begin your application: https://app.hobsons.co.uk/?id=madrid-mit

      Read Full Article
    8. Eye Biometry Using Quantitative 3-D OCT

      Eye Biometry Using Quantitative 3-D OCT

      Cataracts cause the crystalline lens of the eye to progressively lose its transparency, which decreases vision.   It is one of the major causes of vision loss in our aging population.   Modern cataract surgery involves the replacement of the cloudy lens with an intraocullar lens (IOL).  IOL designs are becomeing more sophisticated, with benefits such as aspheric surfaces, multifocality, and the capability to change position ore shape to restore accommodation.  

      Read Full Article
    9. Intraocular lens alignment from an en face optical coherence tomography image Purkinje-like method

      Intraocular lens alignment from an en face optical coherence tomography image Purkinje-like method

      Measurement of intraocular lens (IOL) alignment implanted in patients in cataract surgery is important to understand their optical performance. We present a method to estimate tilt and decentration of IOLs based on optical coherence tomography (OCT) images. En face OCT images show Purkinje-like images that correspond to the specular reflections from the corneal and IOL surfaces. Unlike in standard Purkinje-imaging, the tomographic nature of OCT allows unequivocal association of the reflection with the corresponding surface. The locations of the Purkinje-like images are linear combinations of IOL tilt, IOL decentration, and eye rotation. The weighting coefficients depend on the individual anterior ...

      Read Full Article
    10. Ocular and Optical Coherence Tomography-Based Corneal Aberrometry in Keratoconic Eyes Treated by Intracorneal Ring Segments

      Ocular and Optical Coherence Tomography-Based Corneal Aberrometry in Keratoconic Eyes Treated by Intracorneal Ring Segments

      Purpose To analyze corneal and total aberrations using custom-developed anterior segment spectral optical coherence tomography (OCT) and laser ray tracing in keratoconic eyes implanted with intracorneal ring segments (ICRS). Design Evaluation of technology. Prospective study. Case series. Methods Nineteen keratoconic eyes were measured before and after ICRS surgery. Anterior and posterior corneal topographic and pachymetric maps were obtained pre- and postoperatively from 3-dimensional OCT images of the anterior segment, following automatic image analysis and distortion correction. The pupil center coordinates were used as reference for estimation of corneal aberrations. Corneal aberrations were estimated by computational ray tracing on the anterior ...

      Read Full Article
    11. Three-Dimensional Evaluation of Accommodating Intraocular Lens Shift and Alignment In Vivo

      Three-Dimensional Evaluation of Accommodating Intraocular Lens Shift and Alignment In Vivo

      Objective To quantify 3-dimensionally the anterior segment geometry, biometry, and lens position and alignment in patients before and after implantation of the Crystalens-AO (Bausch & Lomb, Rochester, NY) accommodating intraocular lens (A-IOL). Design Prospective, observational study. Participants Ten patients (20 eyes) with cataract before and after implantation of the Crystalens-AO A-IOL. Methods Custom full anterior segment 3-dimensional (3-D) spectral optical coherence tomography (OCT) provided with quantification tools was used to image the cornea, iris, and natural lens preoperatively and intraocular lens postoperatively. Measurements were obtained under phenylephrine preoperatively and under natural viewing conditions and phenylephrine (for accommodative efforts ranging from 0 ...

      Read Full Article
    12. Quantitative OCT-based Longitudinal Evaluation of Intracorneal Ring Segment Implantation in Keratoconus

      Quantitative OCT-based Longitudinal Evaluation of Intracorneal Ring Segment Implantation in Keratoconus

      PURPOSE. To characterize the geometrical properties of keratoconic corneas and upon intracorneal ring segments (ICRS) implantation, using custom-developed Optical Coherence Tomography (OCT). METHODS. Ten keratoconic corneas were measured pre and post-ICRS surgery (7, 30, 90 days). Corneal topographic and pachymetric maps were obtained from 3-D images acquired with OCT, provided with custom algorithms for image analysis, distortion correction, and quantification. The 3-D positioning of the ICRS was also estimated longitudinally, relative to the pupil center and iris plane. RESULTS. Pre-operatively, the average corneal radii of curvature were 7.02±0.54 mm (anterior) and 5.40±0.77 mm (posterior ...

      Read Full Article
    13. Full OCT anterior segment biometry: an application in cataract surgery

      Full OCT anterior segment biometry: an application in cataract surgery

      In vivo three-dimensional (3-D) anterior segment biometry before and after cataract surgery was analyzed by using custom high-resolution high-speed anterior segment spectral domain Optical Coherence Tomography (OCT). The system was provided with custom algorithms for denoising, segmentation, full distortion correction (fan and optical) and merging of the anterior segment volumes (cornea, iris, and crystalline lens or IOL), to provide fully quantitative data of the anterior segment of the eye. The method was tested on an in vitro artificial eye with known surfaces geometry at different orientations and demonstrated on an aging cataract patient in vivo . Biometric parameters CCT, ACD/ILP ...

      Read Full Article
    14. 3-year Postdoctoral Advanced Fellowship in Biomedical Imaging (Visual Optics and Biophotonics Lab, Institute of Optics, CSIC, Madrid)

      3-year Postdoctoral Advanced Fellowship in Biomedical Imaging (Visual Optics and Biophotonics Lab, Institute of Optics, CSIC, Madrid)

      The Visual Optics and Biophotonics Lab ( http://www.vision.csic.es ) seeks candidates for a 3-year Advanced Fellowship Application in Biomedical Imaging to develop projects of excellence/innovation in the area of ocular imaging (OCT and Advanced Microscopy) and Vision Correction The Advanced Fellowship *The Advanced Fellowship is partially funded by the European Commission (FP7 Marie Curie Program), Fundacion Madrid+d (Cofund Program) and VIOBIO Laboratory Funds, and it is part of the Madrid-MIT M+Vision Consortium * First year Fellowship: € 43,000 + € 2,300 as an academic stipend +€ 3,300 as travel funds Second + Third year contract: € 65,000 (gross ...

      Read Full Article
    15. Feature Of The Week 11/4/12: Researchers from the Spanish National Research Council Report on 3D In-Vivo Mapping of Human Lens Topography

      Feature Of The Week 11/4/12: Researchers from the Spanish National Research Council Report on 3D In-Vivo Mapping of Human Lens Topography

      Accurate measurement of the crystalline lens geometry is crucial in the understanding of crystalline lens optical properties, and of the physical changes of the lens in accommodation and presbyopia. It is also helpful the design and evaluation of accommodation-restoration solutions for presbyopia, and to increase the predictability of intraocular lens implantation procedures. In previous works the Visual Optics and Biophotonics research group at the Instituto de Optica "Daza de Valdes" (Spanish National Research Council) Reported the anterior corneal elevation maps obtained by OCT and the evaluation of a Keratoconic eye before and after Intra Corneal ring segments implantation. Recently, the ...

      Read Full Article
    16. In vivo human crystalline lens topography

      In vivo human crystalline lens topography

      Custom high-resolution high-speed anterior segment spectral domain optical coherence tomography (OCT) was used to characterize three-dimensionally (3-D) the human crystalline lens in vivo. The system was provided with custom algorithms for denoising and segmentation of the images, as well as for fan (scanning) and optical (refraction) distortion correction, to provide fully quantitative images of the anterior and posterior crystalline lens surfaces. The method was tested on an artificial eye with known surfaces geometry and on a human lens in vitro, and demonstrated on three human lenses in vivo. Not correcting for distortion overestimated the anterior lens radius by 25% and ...

      Read Full Article
    17. Distortion Correction of OCT Images of the Crystalline Lens: Gradient Index Approach

      Distortion Correction of OCT Images of the Crystalline Lens: Gradient Index Approach

      Purpose. To propose a method to correct optical coherence tomography (OCT) images of posterior surface of the crystalline lens incorporating its gradient index (GRIN) distribution and explore its possibilities for posterior surface shape reconstruction in comparison to existing methods of correction. Methods. Two-dimensional images of nine human lenses were obtained with a time-domain OCT system. The shape of the posterior lens surface was corrected using the proposed iterative correction method. The parameters defining the GRIN distribution used for the correction were taken from a previous publication. The results of correction were evaluated relative to the nominal surface shape (accessible in ...

      Read Full Article
    18. Quantitative OCT-based corneal topography in keratoconus with intracorneal ring segments

      Quantitative OCT-based corneal topography in keratoconus with intracorneal ring segments

      Custom high-resolution high-speed anterior segment spectral domain Optical Coherence Tomography (OCT) was used to characterize three-dimensionally (3-D) corneal topography in keratoconus before and after implantation of intracorneal ring segments (ICRS). Previously described acquisition protocols were followed to minimize the impact of the motions of the eye. The collected set of images was corrected from distortions: fan (scanning) and optical (refraction). Custom algorithms were developed for automatic detection and classification of volumes in the anterior segment of the eye, in particular for the detection and classification of the implanted ICRS. Surfaces were automatically detected for quantitative analysis of the corneal elevation ...

      Read Full Article
    19. Dynamic OCT measurement of corneal deformation by an air puff in normal and cross-linked corneas

      Dynamic OCT measurement of corneal deformation by an air puff in normal and cross-linked corneas

      A new technique is presented for the non-invasive imaging of the dynamic response of the cornea to an air puff inducing a deformation. A spectral OCT instrument combined with an air tonometer in a non-collinear configuration was used to image the corneal deformation over full corneal cross-sections, as well as to obtain high speed measurements of the temporal evolution of the corneal apex. The entire deformation process can be dynamically visualized. A quantitative analysis allows direct extraction of several deformation parameters, such as amplitude, diameter and volume of the maximum deformation, as well as duration and speed of the increasing ...

      Read Full Article
    20. Making anterior segment OCT an accurate corneal topographer: an offer for patent licensing

      Making anterior segment OCT an accurate corneal topographer: an offer for patent licensing

      CISC Press Release - Anterior segment optical OCT holds promise to become an all-in-one instrument for anterior ocular segment specialists, providing not only high-resolution imaging of structures such as the cornea or iridiocorneal angle, but also quantitative information for biometry and topography of the ocular surfaces. The high speed of the new OCT technology (such as spectral or swept source) has allowed for the rapid acquisitions required in the clinic. OCT has the potential to provide accurate anterior and posterior corneal shapes, pachymetry or interocular distances, but to date, extracting this information has been limited by the presence of distortions, which ...

      Read Full Article
    21. Corneal topography from spectral optical coherence tomography (sOCT)

      Corneal topography from spectral optical coherence tomography (sOCT)

      We present a method to obtain accurate corneal topography from a spectral optical coherence tomography (sOCT) system. The method includes calibration of the device, compensation of the fan (or field) distortion introduced by the scanning architecture, and image processing analysis for volumetric data extraction, segmentation and fitting. We present examples of three-dimensional (3-D) surface topography measurements on spherical and aspheric lenses, as well as on 10 human corneas in vivo. Results of sOCT surface topography (with and without fan-distortion correction) were compared with non-contact profilometry (taken as reference) on a spherical lens, and with non-contact profilometry and state-of-the art commercial ...

      Read Full Article
    22. Accuracy of the reconstruction of the crystalline lens gradient index with optimization methods from Ray Tracing and Optical Coherence Tomography data

      Accuracy of the reconstruction of the crystalline lens gradient index with optimization methods from Ray Tracing and Optical Coherence Tomography data

      The accuracy of the reconstruction of the Gradient Refractive Index (GRIN) of the crystalline lens from optimization methods was evaluated. Different input data, including direction cosines of deflected rays, ray impacts obtained from ray tracing and optical path differences from Optical Coherence Tomography (OCT) were studied. Three different GRIN models were analyzed. The experimental errors of the different experimental input data were estimated from comparisons of measurements and simulations using artificial lenses of known geometries. The experimental errors in the surfaces shape measurement and the influence of the number of rays were also considered. OCT-based input data produced the most ...

      Read Full Article
    23. Distortions of the posterior surface in optical coherence tomography images of the isolated crystalline lens: effect of the lens index gradient

      Distortions of the posterior surface in optical coherence tomography images of the isolated crystalline lens: effect of the lens index gradient

      We quantify the posterior surface distortions in optical coherence tomography (OCT) images of isolated crystalline lenses. The posterior radius of curvature and asphericity obtained from OCT images acquired with the beam incident first on the anterior, and then the posterior, surface were compared. The results were compared with predictions of a ray-tracing model which includes the index gradient. The results show that the error in the radius of curvature is within the measurement reproducibility and that it can be corrected by assuming a uniform refractive index. However, accurate asphericity values require a correction algorithm that takes into account the gradient.

      Read Full Article
    24. Three-dimensional reconstruction of the crystalline lens gradient index distribution from OCT imaging

      Three-dimensional reconstruction of the crystalline lens gradient index distribution from OCT imaging

      We present an optimization method to retrieve the gradient index (GRIN) distribution of the in-vitro crystalline lens from optical path difference data extracted from OCT images. Three-dimensional OCT images of the crystalline lens are obtained in two orientations (with the anterior surface up and posterior surface up), allowing to obtain the lens geometry. The GRIN reconstruction method is based on a genetic algorithm that searches for the parameters of a 4-variable GRIN model that best fits the distorted posterior surface of the lens. Computer simulations showed that, for noise of 5 μm in the surface elevations, the GRIN is recovered ...

      Read Full Article
    1-24 of 27 1 2 »
  1. Categories

    1. Applications:

      Art, Cardiology, Dentistry, Dermatology, Developmental Biology, Gastroenterology, Gynecology, Microscopy, NDE/NDT, Neurology, Oncology, Ophthalmology, Other Non-Medical, Otolaryngology, Pulmonology, Urology
    2. Business News:

      Acquisition, Clinical Trials, Funding, Other Business News, Partnership, Patents
    3. Technology:

      Broadband Sources, Probes, Tunable Sources
    4. Miscellaneous:

      Jobs & Studentships, Student Theses, Textbooks
  2. Topics in the News

    1. (27 articles) Spanish National Research Council
    2. (27 articles) Susana Marcos
    3. (17 articles) Sergio Ortiz
    4. (6 articles) Damian Siedlecki
    5. (3 articles) Nicolaus Copernicus University
    6. (3 articles) Maciej Wojtkowski
    7. (2 articles) Harvard University
    8. (2 articles) Massachusetts General Hospital
    9. (2 articles) Seok-Hyun Yun
    10. (2 articles) Maciej Szkulmowski
  3. Popular Articles

  4. Picture Gallery

    Anterior segment imaging with Spectral OCT system using a high-speed CMOS camera Optical distortion correction in Optical Coherence Tomography for quantitative ocular anterior segment by three-dimensional imaging Three-dimensional reconstruction of the crystalline lens gradient index distribution from OCT imaging Distortions of the posterior surface in optical coherence tomography images of the isolated crystalline lens: effect of the lens index gradient Accuracy of the reconstruction of the crystalline lens gradient index with optimization methods from Ray Tracing and Optical Coherence Tomography data Corneal topography from spectral optical coherence tomography (sOCT) Making anterior segment OCT an accurate corneal topographer: an offer for patent licensing Distortion Correction of OCT Images of the Crystalline Lens: Gradient Index Approach Feature Of The Week 11/4/12: Researchers from the Spanish National Research Council Report on 3D In-Vivo Mapping of Human Lens Topography 3-year Postdoctoral Advanced Fellowship in Biomedical Imaging (Visual Optics and Biophotonics Lab, Institute of Optics, CSIC, Madrid) How Innovation In Healthcare Sector Has Improved Patient Outcomes Real-time digital signal processing-based optical coherence tomography and Doppler optical coherence tomography