1. Articles from fabrice manns

    1-17 of 17
    1. Combined anterior segment OCT and wavefront-based autorefractor using a shared beam

      Combined anterior segment OCT and wavefront-based autorefractor using a shared beam

      We have combined an anterior segment (AS) optical coherence tomography (OCT) system and a wavefront-based aberrometer with an approach that senses ocular wavefront aberrations using the OCT beam. Temporal interlacing of the OCT and aberrometer channels allows for OCT images and refractive error measurements to be acquired continuously and in real-time. The system measures refractive error with accuracy and precision comparable to that of clinical autorefractors. The proposed approach provides a compact modular design that is suitable for integrating OCT and wavefront-based autorefraction within the optical head of the ophthalmic surgical microscope for guiding cataract surgery or table-top devices for ...

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    2. Off-axis optical coherence tomography imaging of the crystalline lens to reconstruct the gradient refractive index using optical methods

      Off-axis optical coherence tomography imaging of the crystalline lens to reconstruct the gradient refractive index using optical methods

      Earlier studies have shown that the gradient index of refraction (GRIN) of the crystalline lens can be reconstructed in vitro using Optical Coherence Tomography (OCT) images. However, the methodology cannot be extended in vivo because it requires accurate measurements of the external geometry of the lens. Specifically, the posterior surface is measured by flipping the lens so that the posterior lens surface faces the OCT beam, a method that cannot be implemented in vivo . When the posterior surface is imaged through the lens in its natural position, it appears distorted by the unknown GRIN. In this study, we demonstrate a ...

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    3. Variability of manual ciliary muscle segmentation in optical coherence tomography images

      Variability of manual ciliary muscle segmentation in optical coherence tomography images

      Optical coherence tomography (OCT) offers new options for imaging the ciliary muscle allowing direct in vivo visualization. However, variation in image quality along the length of the muscle prevents accurate delineation and quantification of the muscle. Quantitative analyses of the muscle are accompanied by variability in segmentation between examiners and between sessions for the same examiner. In processes such as accommodation where changes in muscle thickness may be tens of microns- the equivalent of a small number of image pixels, differences in segmentation can influence the magnitude and potentially the direction of thickness change. A detailed analysis of variability in ...

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    4. Feature Of The Week 03/22/15: Assessing Age-Related Changes in the Biomechanical Properties of Rabbit Lens using a Co-Focused Ultrasound and Optical Coherence Elastography System

      Feature Of The Week 03/22/15: Assessing Age-Related Changes in the Biomechanical Properties of Rabbit Lens using a Co-Focused Ultrasound and Optical Coherence Elastography System

      Presbyopia, the progressive, age-related loss of accommodation power of the eye, is closely related to the viscoelastic properties of the crystalline lens and their alterations by aging. The increase in lens stiffness is generally believed to be responsible for the progressive loss of the ability of the lens to change shape, leading to presbyopia. Noninvasive measurements of mechanical properties of the lens in vivo will promote the comprehensive understandings of the mechanism of accommodation and presbyopia, as well as help in developing new approaches for presbyopia treatment. In this work, we have studied the age-related changes in the biomechanical properties ...

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    5. Retinal imaging system for the mouse or rat or other small animals

      Retinal imaging system for the mouse or rat or other small animals

      A small animal imaging system comprising a base element and a camera coupled to the base element, the camera being sized to image the eye of a small animal. A light-emitting diode is also included coupled to the base element. An OCT imaging apparatus is also included coupled to the base element. An X-Y scanner is also included coupled to the base element in communication with the OCT imaging apparatus.

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    6. Assessing Age-Related Changes in the Biomechanical Properties of Rabbit Lens Using a Coaligned Ultrasound and Optical Coherence Elastography System

      Assessing Age-Related Changes in the Biomechanical Properties of Rabbit Lens Using a Coaligned Ultrasound and Optical Coherence Elastography System

      Purpose. To evaluate the capability of a novel, coaligned focused ultrasound and phase-sensitive optical coherence elastography (US-OCE) system to assess age-related changes in biomechanical properties of the crystalline lens in situ. Methods. Low-amplitude elastic deformations in young and mature rabbit lenses were measured by an US-OCE system consisting of a spectral-domain optical coherence tomography (OCT) system coaligned with a focused ultrasound system used to produce a transient force on the lens surface. Uniaxial compressional tests were used to validate the OCE data. Results. The OCE measurements showed that the maximum displacements of the young rabbit lenses were significantly larger than ...

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    7. Assessing age-related changes in the biomechanical properties of rabbit lens using a co-aligned ultrasound and optical coherence elastography system

      Assessing age-related changes in the biomechanical properties of rabbit lens using a co-aligned ultrasound and optical coherence elastography system

      Purpose: To evaluate the capability of a novel co-aligned focused ultrasound and phase-sensitive optical coherence elastography (US-OCE) system to assess age-related changes in biomechanical properties of the crystalline lens in situ. Methods: Low-amplitude elastic deformations in young and mature rabbit lenses were measured by the US-OCE system consisting of a spectral-domain optical coherence tomography (OCT) system co-aligned with focused ultrasound used to produce a transient force on the lens surface. Uniaxial compressional tests were used to confirm the OCE data. Results: The OCE measurements showed that the maximum displacements of the young rabbit lenses were significantly larger than those of ...

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    8. Combining optical coherence tomography with acoustic radiation force for depth-dependent biomechanics of crystalline lens

      Combining optical coherence tomography with acoustic radiation force for depth-dependent biomechanics of crystalline lens

      Noninvasively probing the biomechanical properties of crystalline lens has been challenging due to its unique features such as location inside the eye and being optically and ultrasonically transparent. Here we introduce a method of relying on the spectral analysis of the lens surface response to a mechanical stimulation for the depthdependent assessment of lens biomechanical properties. In this method, acoustic radiation force (ARF) is used to remotely induce the deformation on the surface of the crystalline lens, and a phase-sensitive optical coherence tomography (PhS-OCT) system, co-focused with ARF, utilized to monitor the localized temporal response of ARFinduced deformations on the ...

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    9. Biometry of the ciliary muscle during dynamic accommodation assessed with OCT

      Biometry of the ciliary muscle during dynamic accommodation assessed with OCT

      Little is known about the structural changes of the ciliary muscle with age and how it may contribute to presbyopia. Optical coherence tomography (OCT) has been used to perform ciliary muscle biometry at different age and accommodative states with low resolution and speed. Dynamic imaging and accurate biometry of the ciliary muscle requires high-speed, high-resolution and correction of the OCT image distortions. We integrate an existing custom-made Spectral Domain OCT (SD-OCT) platform working at 840nm for biometry of the human eye with a SD-OCT system working at 1325nm that enables high-speed and high-resolution transscleral imaging of the ciliary muscle dynamically ...

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    10. Assessing the mechanical properties of tissue-mimicking phantoms at different depths as an approach to measure biomechanical gradient of crystalline lens

      Assessing the mechanical properties of tissue-mimicking phantoms at different depths as an approach to measure biomechanical gradient of crystalline lens

      We demonstrate the feasibility of using the dominant frequency of the sample surface response to a mechanical stimulation as an effective indicator for sensing the depthwise distribution of elastic properties in transparent layered phantom samples simulating the cortex and nucleus of the crystalline lens. Focused ultrasound waves are used to noninvasively interrogate the sample surface. A phase-sensitive optical coherence tomography system is utilized to capture the surface dynamics over time with nanometer scale sensitivity. Spectral analysis is performed on the sample surface response to ultrasound stimulation and the dominant frequency is calculated under particular loading parameters. Pilot experiments were conducted ...

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    11. Intraoperative imaging system and apparatus

      Intraoperative imaging system and apparatus

      Systems, methods and apparatuses for intraocular imaging system are disclosed comprising an optical coherence tomography (OCT) system. The OCT system has an imaging range that may enable substantial portions of an eye to be imaged. The OCT system may be coupled to an operation microscope, such that, for example, a surgeon can visualize ocular structures like the human crystalline lens and other ocular structures such as the cornea and/or vitreous while surgical instruments are in the field of view.

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    12. In vivo measurement of the average refractive index of the human crystalline lens using optical coherence tomography

      In vivo measurement of the average refractive index of the human crystalline lens using optical coherence tomography

      We present a method for measuring the average group refractive index of the human crystalline lens in vivo using an optical coherence tomography (OCT) system which, allows full-length biometry of the eye. A series of OCT images of the eye including the anterior segment and retina were recorded during accommodation. Optical lengths of the anterior chamber, lens, and vitreous were measured dynamically along the central axis on the OCT images. The group refractive index of the crystalline lens along the central axis was determined using linear regression analysis of the intraocular optical length measurements. Measurements were acquired on three subjects ...

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    13. 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 ...

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    14. 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.

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    15. Small animal ocular biometry using optical coherence tomography

      Small animal ocular biometry using optical coherence tomography

      A custom-built OCT system was used to obtain images of the whole mouse eye. We developed a semi-automated segmentation method to detect the boundaries of the anterior and posterior corneal, lens and retinal surfaces as well as the anterior surface of the iris. The radii of curvature of the surfaces were calculated using a conic section fit of each boundary. Image distortions due to refraction of the OCT beam at the successive boundaries were corrected using a ray-tracing algorithm. Corrected ocular distances, radii of curvature of the cornea and lens surfaces, and anterior chamber angle were obtained on 3 C57BL ...

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    16. Refractive index measurement of the isolated crystalline lens using optical coherence tomography

      An optical coherence tomography system has been developed that was designed specifically for imaging the isolated crystalline lens. Cross-sectional OCT images were recorded on 40 lenses from 32 human donors with an age range of 6–82 years. A method has been developed to measure the axial thickness and average refractive index of the lens from a single recorded image. The measured average group refractive index at the measurement wavelength of 825 nm was converted to the average phase refractive index at 589 nm using lens dispersion data from the literature. The average refractive index for all lenses measured was ...

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    17. One-Year Results and Anterior Segment Optical Coherence Tomography Findings of Descemet Stripping Automated Endothelial Keratoplasty Combined With Phacoemulsification

      Objective  To report 1-year results and anterior segment optical coherence tomography findings of Descemet stripping automated endothelial keratoplasty combined with phacoemulsification in patients with cataract and Fuchs endothelial dystrophy. Methods  Twelve eyes of 11 patients with at least 1-year follow-up were retrospectively reviewed. Measured variables included best spectacle-corrected visual acuity, refractive spherical equivalent and predictability, anterior corneal keratometric values, complications, and anterior segment optical coherence tomography findings. Results  The mean follow-up was 14.33 months (range, 12-18 months). The best spectacle-corrected visual acuity was unchanged (8%) or improved (92%) in all eyes compared with the preoperative levels. A mean (SD ...
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    1-17 of 17
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    Small animal ocular biometry using optical coherence tomography Distortions of the posterior surface in optical coherence tomography images of the isolated crystalline lens: effect of the lens index gradient Distortion Correction of OCT Images of the Crystalline Lens: Gradient Index Approach In vivo measurement of the average refractive index of the human crystalline lens using optical coherence tomography Intraoperative imaging system and apparatus Assessing the mechanical properties of tissue-mimicking phantoms at different depths as an approach to measure biomechanical gradient of crystalline lens Assessing age-related changes in the biomechanical properties of rabbit lens using a co-aligned ultrasound and optical coherence elastography system Feature Of The Week 03/22/15: Assessing Age-Related Changes in the Biomechanical Properties of Rabbit Lens using a Co-Focused Ultrasound and Optical Coherence Elastography System Cascade Optical Coherence Tomography (C-OCT) for Surface Form Metrology of - ProQuest Comparison of Anterior Segment Measurements with a New Multifunctional Unit and Five Other Devices Efficacy of Notal Vision Home OCT demonstrated by a series of scientific and clinical work Synergy Between morpHOlogical and inflammatoRy Evaluation in Predicting Long-term Coronary Plaque Progression