1. Articles from Pablo Pérez-Merino

    1-15 of 15
    1. Estimation of intraocular lens position from full crystalline lens geometry: towards a new generation of intraocular lens power calculation formulas

      Estimation of intraocular lens position from full crystalline lens geometry: towards a new generation of intraocular lens power calculation formulas

      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 ...

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    2. 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 ...

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    3. 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 ...

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    4. 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 ...

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    5. 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 ...

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    6. 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 ...

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    7. Static and dynamic crystalline lens accommodation evaluated using quantitative 3-D OCT

      Static and dynamic crystalline lens accommodation evaluated using quantitative 3-D OCT

      Custom high-resolution high-speed anterior segment spectral domain Optical Coherence Tomography (OCT) provided with automatic quantification and distortion correction algorithms was used to characterize three-dimensionally (3-D) the human crystalline lens in vivo in four subjects, for accommodative demands between 0 to 6 D in 1 D steps. Anterior and posterior lens radii of curvature decreased with accommodative demand at rates of 0.73 and 0.20 mm/D, resulting in an increase of the estimated optical power of the eye of 0.62 D per diopter of accommodative demand. Dynamic fluctuations in crystalline lens radii of curvature, anterior chamber depth and ...

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    8. 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 ...

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    9. 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 ...

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    10. 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 ...

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    11. 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 ...

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    12. 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 ...

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    13. 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 ...

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    14. 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 ...

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    15. 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 ...

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    1-15 of 15
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    1. (15 articles) Spanish National Research Council
    2. (2 articles) Nicolaus Copernicus University
    3. (1 articles) Harvard University
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    Corneal topography from spectral optical coherence tomography (sOCT) Quantitative OCT-based corneal topography in keratoconus with intracorneal ring segments Dynamic OCT measurement of corneal deformation by an air puff in normal and cross-linked corneas In vivo human crystalline 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 Full OCT anterior segment biometry: an application in cataract surgery Quantitative OCT-based Longitudinal Evaluation of Intracorneal Ring Segment Implantation in Keratoconus Three-Dimensional Evaluation of Accommodating Intraocular Lens Shift and Alignment In Vivo Static and dynamic crystalline lens accommodation evaluated using quantitative 3-D OCT OCT-based full crystalline lens shape change during accommodation in vivo The Structural and Comparative Analysis of Intravitreal Dexamethasone Implant (Ozurdex) and Anti-VEGF Injection in Branched Retinal Vein Occlusion Patients by Optical Coherence Tomography Angiography Images Quantitation Vascular Responses to First-Generation Sirolimus-Eluting Stents and Bare-Metal Stents Beyond 10 Years