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Dolling M, Buhl L, Birngruber R, Hüttmann G, Schulz-Hildebrandt H. Algorithm and software for field distortion correction in a commercial SD-OCT for corneal curvature assessment. APPLIED OPTICS 2024; 63:2694-2703. [PMID: 38568554 DOI: 10.1364/ao.505107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 03/12/2024] [Indexed: 04/05/2024]
Abstract
Accurate assessment of corneal curvatures using frequency domain optical coherence tomography (OCT) with galvanometer scanners remains challenging due to the well-known scan field distortion. This paper presents an algorithm and software for correcting the distortion using only two simple measurements in which a readily available standard sphere is positioned in different depths in front of the OCT scanner. This offers a highly accessible and easily reproducible method for the field distortion correction (FDC). The correction was validated by measuring different spherical phantoms and conducting corneal curvature measurements of ex vivo porcine corneas using a commercial spectral-domain OCT system and a clinically approved swept-source OCT as a reference instrument. Thus, the error in radius measurements of spherical phantoms was reduced by >90% and astigmatism by >80% using FDC. In explanted porcine eyes, the error in astigmatism measurements with the Telesto was reduced by 75% for power and 70% for angle. The best fitting sphere radius was determined up to a deviation of 0.4% from the Anterion. This paper describes a correction algorithm for OCT immanent distortion that is applicable to any scanning OCT setup and enables precise corneal curvature measurements. The MATLAB software for the FDC is publicly available on GitHub.
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Mallada SO, Yebra DG, Zardoya NT, García JA. Using clinical optical coherence tomography to characterise contact lens edge shape and base curve radius. Clin Exp Optom 2024:1-9. [PMID: 38224567 DOI: 10.1080/08164622.2024.2302832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 11/28/2023] [Indexed: 01/17/2024] Open
Abstract
CLINICAL RELEVANCE Clinical optical coherence tomography devices are widely used in optometry and ophthalmology and may be used to measure contact lens base curvature radius and visualise contact lens edge shape. BACKGROUND Knowledge of contact lens geometry facilitates fitting, while optical coherence tomography provides a powerful means of measuring geometrical form. This study evaluates the performance of a clinical optical coherence tomography device (3D OCT-1000) in characterising contact lens edge shape and measuring the back optic zone radius of rigid gas-permeable contact lenses in vitro. METHODS First, an opto-mechanical optical coherence tomography contact lens adaptor was designed and 3D-printed to facilitate a contact lens being imaged using a commercial optical coherence tomography device. Second, several image-processing algorithms and a simple calibration method were developed to measure the back optic zone radius in optical coherence tomography B-scans. Finally, based on the findings of two experiments, B-scan performance was evaluated in terms of 1) capacity to differentiate between contact lens edge geometries, and 2) capacity to obtain accurate and repeatable back optic zone radius measurements. Statistical and graphical analyses were performed to characterise reliability and reproducibility. RESULTS The 3D OCT-1000 and adaptor combination was capable of acquiring images of sufficient quality to discriminate between soft and rigid contact lens edge geometries. Additionally, statistical analysis of the rigid contact lens measurements demonstrated satisfactory back optic zone radius measurement accuracy and reproducibility. CONCLUSION This study demonstrates that a 3D OCT-1000 fitted with an opto-mechanical adaptor combination can be used to assess contact lens edges in vitro and that this clinical optical coherence tomography device, combined with image processing and linear calibration of the B-scans, is capable of obtaining back optic zone radius measurements of rigid gas-permeable contact lenses that are close to the ISO 18,369-2:2018 manufacturing tolerance range (±0.05 mm).
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Martínez-Enríquez E, Maceo Heilman B, de Castro A, Mohamed A, Ruggeri M, Zvietcovich F, Manns F, Marcos S. Estimation of the full shape of the crystalline lens from OCT: validation using stretched donor lenses. BIOMEDICAL OPTICS EXPRESS 2023; 14:4261-4276. [PMID: 37799671 PMCID: PMC10549758 DOI: 10.1364/boe.493795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 06/17/2023] [Accepted: 06/19/2023] [Indexed: 10/07/2023]
Abstract
Quantifying human crystalline lens geometry as a function of age and accommodation is important for improved cataract and presbyopia treatments. In previous works we presented eigenlenses as a basis of 3-D functions to represent the full shape of the crystalline lens ex vivo. Also, we presented the application of eigenlenses to estimate the full shape of the lens in vivo from 3-D optical coherence tomography (OCT) images, where only the central part of the lens -visible through the pupil- is available. The current work presents a validation of the use of eigenlenses to estimate in vivo the full shape of dis-accommodated lenses. We used 14 ex vivo crystalline lenses from donor eyes (11-54 y/o) mounted in a lens stretcher, and measured the geometry and the power of the lenses using a combined OCT and ray tracing aberrometry system. Ex vivo, the full extent of the lens is accessible from OCT because the incident light is not blocked by the iris. We measured in non-stretched (fully accommodated) and stretched (mimicking in vivo dis-accommodated lenses) conditions. Then, we simulated computationally in vivo conditions on the obtained ex vivo lenses geometry (assuming that just the portion of the lens within a given pupil is available), and estimated the full shape using eigenlenses. The mean absolute error (MAE) between estimated and measured lens' diameters and volumes were MAE = 0.26 ± 0.18 mm and MAE = 7.0 ± 4.5 mm3, respectively. Furthermore, we concluded that the estimation error between measured and estimated lenses did not depend on the accommodative state (change in power due to stretching), and thus eigenlenses are also useful for the full shape estimation of in vivo dis-accommodated lenses.
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Affiliation(s)
| | - Bianca Maceo Heilman
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Alberto de Castro
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Madrid, Spain
| | - Ashik Mohamed
- Ophthalmic Biophysics, LV Prasad Eye Institute, Hyderabad, Telangana, India
- Brien Holden Vision Institute, Sydney, NSW, Australia
| | - Marco Ruggeri
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, FL, USA
| | - Fernando Zvietcovich
- Department of Engineering, Pontificia Universidad Católica del Peru, Lima 15088, Peru
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Susana Marcos
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Madrid, Spain
- Center for Visual Science. The Institute of Optics. Flaum Eye Institute, University of Rochester, Rochester, NY, USA
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de Castro A, Martínez-Enríquez E, Marcos S. Effect of fixational eye movements in corneal topography measurements with optical coherence tomography. BIOMEDICAL OPTICS EXPRESS 2023; 14:2138-2152. [PMID: 37206127 PMCID: PMC10191639 DOI: 10.1364/boe.486460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/24/2023] [Accepted: 03/25/2023] [Indexed: 05/21/2023]
Abstract
There is an increasing interest in applying optical coherence tomography (OCT) to quantify the topography of ocular structures. However, in its most usual configuration, OCT data is acquired sequentially while a beam is scanned through the region of interest, and the presence of fixational eye movements can affect the accuracy of the technique. Several scan patterns and motion correction algorithms have been proposed to minimize this effect, but there is no consensus on the ideal parameters to obtain a correct topography. We have acquired corneal OCT images with raster and radial patterns, and modeled the data acquisition in the presence of eye movements. The simulations replicate the experimental variability in shape (radius of curvature and Zernike polynomials), corneal power, astigmatism, and calculated wavefront aberrations. The variability of the Zernike modes is highly dependent on the scan pattern, with higher variability in the direction of the slow scan axis. The model can be a useful tool to design motion correction algorithms and to determine the variability with different scan patterns.
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Affiliation(s)
- Alberto de Castro
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Madrid, Spain
| | | | - Susana Marcos
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Madrid, Spain
- Center for Visual Science, The Institute of Optics, Flaum Eye Institute, University of Rochester, Rochester, NY, USA
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6
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Marcos S, Martinez-Enriquez E, Vinas M, de Castro A, Dorronsoro C, Bang SP, Yoon G, Artal P. Simulating Outcomes of Cataract Surgery: Important Advances in Ophthalmology. Annu Rev Biomed Eng 2021; 23:277-306. [PMID: 33848431 DOI: 10.1146/annurev-bioeng-082420-035827] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
As the human eye ages, the crystalline lens stiffens (presbyopia) and opacifies (cataract), requiring its replacement with an artificial lens [intraocular lens (IOL)]. Cataract surgery is the most frequently performed surgical procedure in the world. The increase in IOL designs has not been paralleled in practice by a sophistication in IOL selection methods, which rely on limited anatomical measurements of the eye and the surgeon's interpretation of the patient's needs and expectations. We propose that the future of IOL selection will be guided by 3D quantitative imaging of the crystalline lens to map lens opacities, anticipate IOL position, and develop fully customized eye models for ray-tracing-based IOL selection. Conversely, visual simulators (in which IOL designs are programmed in active elements) allow patients to experience prospective vision before surgery and to make more informed decisions about which IOL to choose. Quantitative imaging and optical and visual simulations of postsurgery outcomes will allow optimal treatments to be selected for a patient undergoing modern cataract surgery.
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Affiliation(s)
- Susana Marcos
- Instituto de Óptica "Daza de Valdés," Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid 28006, Spain;
| | - Eduardo Martinez-Enriquez
- Instituto de Óptica "Daza de Valdés," Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid 28006, Spain;
| | - Maria Vinas
- Instituto de Óptica "Daza de Valdés," Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid 28006, Spain;
| | - Alberto de Castro
- Instituto de Óptica "Daza de Valdés," Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid 28006, Spain;
| | - Carlos Dorronsoro
- Instituto de Óptica "Daza de Valdés," Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid 28006, Spain; .,2EyesVision, Madrid 28760, Spain
| | - Seung Pil Bang
- Flaum Eye Institute, The Institute of Optics, Center for Visual Science, Department of Biomedical Engineering, University of Rochester, Rochester, New York 14632, USA
| | - Geunyoung Yoon
- Flaum Eye Institute, The Institute of Optics, Center for Visual Science, Department of Biomedical Engineering, University of Rochester, Rochester, New York 14632, USA
| | - Pablo Artal
- Laboratorio de Óptica, Universidad de Murcia, Murcia 30100, Spain
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7
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Mohamed A, Nandyala S, Martinez-Enriquez E, Heilman BM, Augusteyn RC, de Castro A, Ruggeri M, Parel JMA, Marcos S, Manns F. Isolated human crystalline lens three-dimensional shape: A comparison between Indian and European populations. Exp Eye Res 2021; 205:108481. [PMID: 33545121 DOI: 10.1016/j.exer.2021.108481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 01/07/2021] [Accepted: 01/26/2021] [Indexed: 11/25/2022]
Abstract
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.
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Affiliation(s)
- Ashik Mohamed
- Ophthalmic Biophysics, L V Prasad Eye Institute, Hyderabad, India; Brien Holden Vision Institute Limited, Sydney, Australia.
| | - Sushma Nandyala
- Ophthalmic Biophysics, L V Prasad Eye Institute, Hyderabad, India
| | - Eduardo Martinez-Enriquez
- Visual Optics and Biophotonics Lab, Institute of Optics, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - Bianca Maceo Heilman
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA; Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Robert C Augusteyn
- Brien Holden Vision Institute Limited, Sydney, Australia; Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Alberto de Castro
- Visual Optics and Biophotonics Lab, Institute of Optics, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - Marco Ruggeri
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA; Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Jean-Marie A Parel
- Brien Holden Vision Institute Limited, Sydney, Australia; Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA; Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA; Anne Bates Leach Eye Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Susana Marcos
- Visual Optics and Biophotonics Lab, Institute of Optics, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA; Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
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8
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Jandl A, Ruland T, Schwarz D, Wolffsohn JS, Pult H, Bandlitz S. Clinical significance of contact lens related changes of ocular surface tissue observed on optical coherence images. Cont Lens Anterior Eye 2020; 44:101388. [PMID: 33293225 DOI: 10.1016/j.clae.2020.11.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 11/12/2020] [Accepted: 11/15/2020] [Indexed: 10/22/2022]
Abstract
PURPOSE To investigate the relationship between the real contact lens imprint into the conjunctival tissue, observed by optical coherence tomography (OCT) and conjunctival staining and contact lens wearing comfort. METHODS 17 participants (mean age = 26.6 SD ± 3.6 years; 7 females) were fitted with three different contact lenses base curves of the same silicone hydrogel custom lens type (Visell 50; Hecht Contactlinsen, Au, Germany) in a randomised order. One lens was optimally fitted according to the manufacturer's recommendation, one fitted 0.4 mm flatter and one fitted 0.4 mm steeper. After 4 h of lens wear the contact lens edge in the area of the conjunctiva was imaged nasally and temporally using OCT (Optovue iVue SD-OCT). To correct the artefact due to optical distortion with OCT, the imprint of all worn lenses was measured on a glass plate afterwards. Conjunctival staining in the limbal region after 4 h of lens wear was classified using the CCLRU Grading Scale. Comfort scoring was based on visual analog scales from 0 (very poor) to 100 (excellent). RESULTS The mean conjunctival imprint of all contact lens edges was 32.0 ± 8.1 μm before and 7.3 ± 6.5 μm after distortion correction of the OCT images. The distortion corrected conjunctival imprint with the 0.4 mm steeper lens (11.5 ± 6.2 μm) was statistically significantly greater compared to the optimally fitted lens (6.5 ± 5.9 μm) (One-way ANOVA followed Tukey-test; p = 0.017) and greater compared to the 0.4 mm flatter lens (3.9 ± 5.3 μm) (p < 0.001). There was no statistically significant difference between the optimally fitted lens and the 0.4 mm flatter lens (p = 0.209). The nasally measured imprint (11.4 ± 9.0 μm) was significantly greater than the temporally measured (3.3 ± 7.6 μm) (p < 0.001). There was no statistically significant correlation between the amount of conjunctival imprint and the graded conjunctival staining (p = 0.346) or the wearer's comfort (p = 0.735). CONCLUSIONS Contact lens edges imaged by OCT exhibited displacement artefacts. The observed conjunctival imprints are a combination of real conjunctival compression and artefacts. A deeper imprint of the contact lens into the conjunctiva caused by a steeper base curve was not related to clinically significant staining or changes in comfort after 4 h of lens wear. The observed differences between nasal and temporal imprint are likely to be caused by variations of conjunctival thickness and the shape of the underlying sclera.
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Affiliation(s)
- Alexandra Jandl
- Höhere Fachschule für Augenoptik Köln, Cologne School of Optometry, Cologne, Germany
| | - Thomas Ruland
- Höhere Fachschule für Augenoptik Köln, Cologne School of Optometry, Cologne, Germany
| | - David Schwarz
- Höhere Fachschule für Augenoptik Köln, Cologne School of Optometry, Cologne, Germany
| | - James S Wolffsohn
- Optometry and Vision Science Research Group, Aston University, Birmingham, United Kingdom
| | - Heiko Pult
- Optometry and Vision Science Research Group, Aston University, Birmingham, United Kingdom; Dr Heiko Pult - Optometry and Vision Research, Weinheim, Germany; School of Biomedical & Life Sciences, Cardiff University, Cardiff, United Kingdom
| | - Stefan Bandlitz
- Höhere Fachschule für Augenoptik Köln, Cologne School of Optometry, Cologne, Germany; Optometry and Vision Science Research Group, Aston University, Birmingham, United Kingdom.
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Pavlatos E, Huang D, Li Y. Eye motion correction algorithm for OCT-based corneal topography. BIOMEDICAL OPTICS EXPRESS 2020; 11:7343-7356. [PMID: 33409001 PMCID: PMC7747916 DOI: 10.1364/boe.412209] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/18/2020] [Accepted: 11/19/2020] [Indexed: 05/30/2023]
Abstract
With its sequential image acquisition, OCT-based corneal topography is often susceptible to measurement errors due to eye motion. We have developed a novel algorithm to detect eye motion and minimize its impact on OCT topography maps. We applied the eye motion correction algorithm to corneal topographic scans acquired using a 70 kHz spectral-domain OCT device. OCT corneal topographic measurements were compared to those from a rotating Scheimpflug camera topographer. The motion correction algorithm provided a 2-4 fold improvement in the repeatability of OCT topography and its agreement with the standard Scheimpflug topographer. The repeatability of OCT Zernike-based corneal mean power, cardinal astigmatism, and oblique astigmatism after motion detection was 0.14 D, 0.28 D, and 0.24 D, respectively. The average differences between the two devices were 0.19 D for simulated keratometry-based corneal mean power, 0.23 D for cardinal astigmatism, and 0.25 D for oblique astigmatism. Our eye motion detection method can be applied to any OCT device, and it therefore represents a powerful tool for improving OCT topography.
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Curatolo A, Birkenfeld JS, Martinez-Enriquez E, Germann JA, Muralidharan G, Palací J, Pascual D, Eliasy A, Abass A, Solarski J, Karnowski K, Wojtkowski M, Elsheikh A, Marcos S. Multi-meridian corneal imaging of air-puff induced deformation for improved detection of biomechanical abnormalities. BIOMEDICAL OPTICS EXPRESS 2020; 11:6337-6355. [PMID: 33282494 PMCID: PMC7687933 DOI: 10.1364/boe.402402] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/07/2020] [Accepted: 09/13/2020] [Indexed: 05/18/2023]
Abstract
Corneal biomechanics play a fundamental role in the genesis and progression of corneal pathologies, such as keratoconus; in corneal remodeling after corneal surgery; and in affecting the measurement accuracy of glaucoma biomarkers, such as the intraocular pressure (IOP). Air-puff induced corneal deformation imaging reveals information highlighting normal and pathological corneal response to a non-contact mechanical excitation. However, current commercial systems are limited to monitoring corneal deformation only on one corneal meridian. Here, we present a novel custom-developed swept-source optical coherence tomography (SSOCT) system, coupled with a collinear air-puff excitation, capable of acquiring dynamic corneal deformation on multiple meridians. Backed by numerical simulations of corneal deformations, we propose two different scan patterns, aided by low coil impedance galvanometric scan mirrors that permit an appropriate compromise between temporal and spatial sampling of the corneal deformation profiles. We customized the air-puff module to provide an unobstructed SSOCT field of view and different peak pressures, air-puff durations, and distances to the eye. We acquired multi-meridian corneal deformation profiles (a) in healthy human eyes in vivo, (b) in porcine eyes ex vivo under varying controlled IOP, and (c) in a keratoconus-mimicking porcine eye ex vivo. We detected deformation asymmetries, as predicted by numerical simulations, otherwise missed on a single meridian that will substantially aid in corneal biomechanics diagnostics and pathology screening.
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Affiliation(s)
- Andrea Curatolo
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | - Judith S. Birkenfeld
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | - Eduardo Martinez-Enriquez
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | - James A. Germann
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | - Geethika Muralidharan
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | | | - Daniel Pascual
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | - Ashkan Eliasy
- Biomechanical Engineering Group, University
of Liverpool, Liverpool, United
Kingdom
| | - Ahmed Abass
- Biomechanical Engineering Group, University
of Liverpool, Liverpool, United
Kingdom
| | - Jędrzej Solarski
- Physical Optics and Biophotonics Group,
Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw,
Poland
| | - Karol Karnowski
- Physical Optics and Biophotonics Group,
Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw,
Poland
| | - Maciej Wojtkowski
- Physical Optics and Biophotonics Group,
Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw,
Poland
| | - Ahmed Elsheikh
- Biomechanical Engineering Group, University
of Liverpool, Liverpool, United
Kingdom
- Beijing Advanced Innovation Centre for
Biomedical Engineering, Beihang University, Beijing, China
- NIHR Biomedical Research Centre for
Ophthalmology, Moorfields Eye Hospital, NHS Foundation Trust, and UCL
Institute of Ophthalmology, United
Kingdom
| | - Susana Marcos
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
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11
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Biometric Measurement of Anterior Segment: A Review. SENSORS 2020; 20:s20154285. [PMID: 32752014 PMCID: PMC7435894 DOI: 10.3390/s20154285] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 07/22/2020] [Accepted: 07/29/2020] [Indexed: 12/12/2022]
Abstract
Biometric measurement of the anterior segment is of great importance for the ophthalmology, human eye modeling, contact lens fitting, intraocular lens design, etc. This paper serves as a comprehensive review on the historical development and basic principles of the technologies for measuring the geometric profiles of the anterior segment. Both the advantages and drawbacks of the current technologies are illustrated. For in vivo measurement of the anterior segment, there are two main challenges that need to be addressed to achieve high speed, fine resolution, and large range imaging. One is the motion artefacts caused by the inevitable and random human eye movement. The other is the serious multiple scattering effects in intraocular turbid media. The future research perspectives are also outlined in this paper.
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12
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The effect of sodium fluorescein on anterior eye surface measurements. Cont Lens Anterior Eye 2020; 43:402-407. [PMID: 32146117 DOI: 10.1016/j.clae.2020.02.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 02/25/2020] [Accepted: 02/25/2020] [Indexed: 11/23/2022]
Abstract
PURPOSE During image acquisition, certain topographers require the addition of sodium fluorescein (NaFl) dye to the tear film. This study investigates the effect of NaFl dye on corneal topography and tear surface quality. METHOD The E300 corneal topographer (Medmont International Pty Ltd., Victoria, Australia) was used to measure ocular surface topography and quality of 57 eyes of 57 healthy individuals without dry eye symptoms, age 35.1 ± 15.2 years (mean ± standard deviation) ranging between 19 and 65 years. The mean of three simulated keratometry values, a variety of corneal shape descriptors, and Tear Film Surface Quality (TFSQ) were measured under three different conditions; without NaFl (baseline), with the addition of a single dose NaFl, and using a double dose of NaFl. RESULTS Compared to baseline, the Inferior-Superior (IS) index decreased significantly after a single dose (P = 0.034) or double dose of NaFl (P = 0.030). The corneal surface was significantly more regular without NaFl (P = 0.003) or one insertion of NaFl (P = 0.024) when compared to two doses of NaFl. There was no association with age, or dry eye signs or symptoms on the variance observed in any of the indices between baseline, intervention I, and intervention II (P > 0.05). Agreement between corneal surface indices reduced following the addition of NaFl. CONCLUSION In comparison to measurements taken without an ocular dye, one dose of NaFl resulted in increased reliability and consistency in corneal topography measurements using the E300 topographer, but 2 doses decreased reliability and consistency. Practitioners ought to be aware that tear film surface regularity and inferior-superior corneal power changed significantly following the addition of NaFl in those with healthy corneas. Its effect in diseased corneas is unknown.
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Muralidharan G, Martínez-Enríquez E, Birkenfeld J, Velasco-Ocana M, Pérez-Merino P, Marcos S. Morphological changes of human crystalline lens in myopia. BIOMEDICAL OPTICS EXPRESS 2019; 10:6084-6095. [PMID: 31853387 PMCID: PMC6913406 DOI: 10.1364/boe.10.006084] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 10/01/2019] [Accepted: 10/02/2019] [Indexed: 05/09/2023]
Abstract
Ocular biometric parameters, including full shape crystalline lens, were assessed in myopes and emmetropes using 3-D optical coherence tomography. The anterior chamber depth, the radius of the curvature of the anterior cornea, anterior lens, and posterior lens, lens thickness, lens equatorial diameter, surface area, equatorial position, volume, and power, were evaluated as functions of refractive errors and axial lengths while controlling for age effects. The crystalline lens appears to change with myopia consistent with lens thinning, equatorial, and capsular stretching while keeping constant volume. Axial elongation appears counteracted by a crystalline lens power reduction, while corneal power remains unaffected.
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Das S, Liu CH, Singh M, Twa MD, Larin KV. Modified wavelength scanning interferometry for simultaneous tomography and topography of the cornea with Fourier domain optical coherence tomography. BIOMEDICAL OPTICS EXPRESS 2018; 9:4443-4458. [PMID: 30615727 PMCID: PMC6157774 DOI: 10.1364/boe.9.004443] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 08/15/2018] [Accepted: 08/16/2018] [Indexed: 05/20/2023]
Abstract
Visual acuity is dependent on corneal shape and size. A minor variation in surface geometry can cause a deformation of corneal geometry, which affects its optical performance. In this work we demonstrate an algorithm for the simultaneous measurement of corneal tomography and topography with a traditional point-scanning Fourier domain optical coherence tomography (FD-OCT) system. A modified wavelength scanning interferometry (mWSI) algorithm enabled topographical evaluation of the surface with nanometer-scale resolution, which is superior to the micrometer-scale resolution of traditional OCT structural imaging. We validated the technique with an optically flat mirror, standard roughness gauges, and atomic force microscopy (AFM). The mirror results show nanometer-scale sensitivity (~3.5 nm), and the mWSI measurements were in good agreement (error ~5%) with the specifications of the roughness comparator and AFM, demonstrating the accuracy of the technique. Following validation, the measurements were made on pig corneas in situ at various artificially controlled intraocular pressures (IOP) and before and after cross-linking (CXL). The results show that the mean surface roughness increased by ~65% after removal of the epithelium in preparation for CXL but did not change as a function of IOP. The demonstrated method could be used for simultaneous measurement of tissue tomography with micrometer-precision and topography with nanometer-precision.
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Affiliation(s)
- Susobhan Das
- Department of Biomedical Engineering, University of Houston, Houston, TX 77004, USA
| | - Chih-Hao Liu
- Department of Biomedical Engineering, University of Houston, Houston, TX 77004, USA
| | - Manmohan Singh
- Department of Biomedical Engineering, University of Houston, Houston, TX 77004, USA
| | - Michael D. Twa
- College of Optometry, University of Alabama, Birmingham, AL 35294, USA
- Department of Biomedical Engineering, University of Alabama, Birmingham, AL 35294, USA
| | - Kirill V. Larin
- Department of Biomedical Engineering, University of Houston, Houston, TX 77004, USA
- Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
- Interdisciplinary Laboratory of Biophotonics, Tomsk State University, Tomsk, Russia
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Ruggeri M, Williams S, Heilman BM, Yao Y, Chang YC, Mohamed A, Sravani NG, Durkee H, Rowaan C, Gonzalez A, Ho A, Parel JM, Manns F. System for on- and off-axis volumetric OCT imaging and ray tracing aberrometry of the crystalline lens. BIOMEDICAL OPTICS EXPRESS 2018; 9:3834-3851. [PMID: 30338159 PMCID: PMC6191619 DOI: 10.1364/boe.9.003834] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 07/17/2018] [Accepted: 07/17/2018] [Indexed: 05/22/2023]
Abstract
We present a new in vitro instrument for measuring shape and wavefront aberrations of the primate crystalline lens, both on- and off-axis, while simulating accommodation with a motorized lens stretching system. The instrument merges spectral domain optical coherence tomography (SD-OCT) imaging and ray tracing aberrometry using an approach that senses wavefront aberrations of the lens with the OCT probing beam. Accuracy and repeatability of aberration measurements were quantified. Preliminary experiments on two human and four cynomolgus monkey lenses demonstrate the ability of the system to measure the lens shape, spherical aberration and peripheral defocus, and their changes during simulated accommodation.
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Affiliation(s)
- Marco Ruggeri
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Siobhan Williams
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Bianca Maceo Heilman
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Yue Yao
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Yu-Cherng Chang
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Ashik Mohamed
- Ophthalmic Biophysics, L V Prasad Eye Institute, Hyderabad, India
- Brien Holden Vision Institute, Sydney, NSW, Australia
- School of Optometry and Vision Science, University of New South Wales, Sydney NSW, Australia
| | | | - Heather Durkee
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Cornelis Rowaan
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Alex Gonzalez
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Arthur Ho
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Brien Holden Vision Institute, Sydney, NSW, Australia
- School of Optometry and Vision Science, University of New South Wales, Sydney NSW, Australia
| | - Jean-Marie Parel
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
- Brien Holden Vision Institute, Sydney, NSW, Australia
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
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Bandlitz S, Bäumer J, Conrad U, Wolffsohn J. Scleral topography analysed by optical coherence tomography. Cont Lens Anterior Eye 2017; 40:242-247. [DOI: 10.1016/j.clae.2017.04.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 04/28/2017] [Accepted: 04/28/2017] [Indexed: 11/28/2022]
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Pérez-merino P, Velasco-Ocana M, Martinez-Enriquez E, Revuelta L, McFadden SA, Marcos S. Three-dimensional OCT based guinea pig eye model: relating morphology and optics. BIOMEDICAL OPTICS EXPRESS 2017; 8:2173-2184. [PMID: 28736663 PMCID: PMC5516822 DOI: 10.1364/boe.8.002173] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 02/14/2017] [Indexed: 05/24/2023]
Abstract
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.
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Affiliation(s)
- Pablo Pérez-merino
- Instituto de Óptica “Daza de Valdés,” Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Miriam Velasco-Ocana
- Instituto de Óptica “Daza de Valdés,” Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Eduardo Martinez-Enriquez
- Instituto de Óptica “Daza de Valdés,” Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Luis Revuelta
- Facultad de Veterinaria, Universidad Complutense, Madrid, Spain
| | - Sally A McFadden
- School of Psychology, University of Newcastle, Newcastle, NSW, Australia
| | - Susana Marcos
- Instituto de Óptica “Daza de Valdés,” Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
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Iyer RV, Nasrin F, See E, Mathews S. Smoothing Splines on Unit Ball Domains with Application to Corneal Topography. IEEE TRANSACTIONS ON MEDICAL IMAGING 2017; 36:518-526. [PMID: 27775513 DOI: 10.1109/tmi.2016.2618389] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Optical coherence tomography (OCT) is a non-invasive imaging technique used to study and understand internal structures of biological tissues such as the anterior chamber of the human eye. An interesting problem is the reconstruction of the shape of the biological tissue from OCT images, that is not only a good fit of the data but also respects the smoothness properties observed in the images. A similar problem arises in Magnetic Resonance Imaging (MRI). We cast the problem as a penalized weighted least squares regression with a penalty on the magnitude of the second derivative (Laplacian) of the surface. We present a novel algorithm to construct the Kimeldorf-Wahba solution for unit ball domains. Our method unifies the ad-hoc approaches currently in the literature. Application of the theory to data from an anterior segment optical coherence tomographer is presented. A detailed comparison of the reconstructed surface using different approaches is presented.
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Martinez-Enriquez E, Pérez-Merino P, Velasco-Ocana M, Marcos S. OCT-based full crystalline lens shape change during accommodation in vivo. BIOMEDICAL OPTICS EXPRESS 2017; 8:918-933. [PMID: 28270993 PMCID: PMC5330589 DOI: 10.1364/boe.8.000918] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 12/15/2016] [Accepted: 12/27/2016] [Indexed: 05/22/2023]
Abstract
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.
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Consejo A, Iskander DR. Corneo-scleral limbus demarcation from 3D height data. Cont Lens Anterior Eye 2016; 39:450-457. [DOI: 10.1016/j.clae.2016.05.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 04/27/2016] [Accepted: 05/02/2016] [Indexed: 11/25/2022]
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Precise measurement of scleral radius using anterior eye profilometry. Cont Lens Anterior Eye 2016; 40:47-52. [PMID: 27863894 DOI: 10.1016/j.clae.2016.11.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2016] [Revised: 10/14/2016] [Accepted: 11/08/2016] [Indexed: 11/23/2022]
Abstract
PURPOSE To develop a new and precise methodology to measure the scleral radius based on anterior eye surface. METHODS Eye Surface Profiler (ESP, Eaglet-Eye, Netherlands) was used to acquire the anterior eye surface of 23 emmetropic subjects aged 28.1±6.6years (mean±standard deviation) ranging from 20 to 45. Scleral radius was obtained based on the approximation of the topographical scleral data to a sphere using least squares fitting and considering the axial length as a reference point. To better understand the role of scleral radius in ocular biometry, measurements of corneal radius, central corneal thickness, anterior chamber depth and white-to-white corneal diameter were acquired with IOLMaster 700 (Carl Zeiss Meditec AG, Jena, Germany). RESULTS The estimated scleral radius (11.2±0.3mm) was shown to be highly precise with a coefficient of variation of 0.4%. A statistically significant correlation between axial length and scleral radius (R2=0.957, p<0.001) was observed. Moreover, corneal radius (R2=0.420, p<0.001), anterior chamber depth (R2=0.141, p=0.039) and white-to-white corneal diameter (R2=0.146, p=0.036) have also shown statistically significant correlations with the scleral radius. Lastly, no correlation was observed comparing scleral radius to the central corneal thickness (R2=0.047, p=0.161). CONCLUSIONS Three-dimensional topography of anterior eye acquired with Eye Surface Profiler together with a given estimate of the axial length, can be used to calculate the scleral radius with high precision.
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Abstract
OBJECTIVE The aim of this study was to develop computational methods for estimating limbus position based on the measurements of three-dimensional (3-D) corneoscleral topography and ascertain whether corneoscleral limbus routinely estimated from the frontal image corresponds to that derived from topographical information. METHODS Two new computational methods for estimating the limbus position are proposed: One based on approximating the raw anterior eye height data by series of Zernike polynomials and one that combines the 3-D corneoscleral topography with the frontal grayscale image acquired with the digital camera in-built in the profilometer. The proposed methods are contrasted against a previously described image-only-based procedure and to a technique of manual image annotation. RESULTS The estimates of corneoscleral limbus radius were characterized with a high precision. The group average (mean ± standard deviation) of the maximum difference between estimates derived from all considered methods was 0.27 ± 0.14 mm and reached up to 0.55 mm. The four estimating methods lead to statistically significant differences (nonparametric ANOVA (the Analysis of Variance) test, p 0.05). CONCLUSION Precise topographical limbus demarcation is possible either from the frontal digital images of the eye or from the 3-D topographical information of corneoscleral region. However, the results demonstrated that the corneoscleral limbus estimated from the anterior eye topography does not always correspond to that obtained through image-only based techniques. SIGNIFICANCE The experimental findings have shown that 3-D topography of anterior eye, in the absence of a gold standard, has the potential to become a new computational methodology for estimating the corneoscleral limbus.
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Iskander DR, Wachel P, Simpson PND, Consejo A, Jesus DA. Principles of operation, accuracy and precision of an Eye Surface Profiler. Ophthalmic Physiol Opt 2016; 36:266-78. [DOI: 10.1111/opo.12292] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Accepted: 02/09/2016] [Indexed: 11/27/2022]
Affiliation(s)
- D. Robert Iskander
- Department of Biomedical Engineering; Wroclaw University of Technology; Wroclaw Poland
| | - Pawel Wachel
- Department of Control Systems and Mechatronics; Wroclaw University of Technology; Wroclaw Poland
| | | | - Alejandra Consejo
- Department of Biomedical Engineering; Wroclaw University of Technology; Wroclaw Poland
| | - Danilo A. Jesus
- Department of Biomedical Engineering; Wroclaw University of Technology; Wroclaw Poland
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Comparison of Tear Meniscus Height Measurements Obtained With the Keratograph and Fourier Domain Optical Coherence Tomography in Dry Eye. Cornea 2016; 34:1209-13. [PMID: 26266429 DOI: 10.1097/ico.0000000000000575] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To study the repeatability and reproducibility of tear meniscus height (TMH) measurements obtained with a keratograph and Fourier domain optical coherence tomography (FD-OCT) and to assess their agreement in patients with dry eye. METHODS Sixty-four eyes with dry eye were analyzed by the Schirmer test, tear breakup time test, and fluorescein corneal staining. The TMH was measured 3 times using both devices by 2 different examiners. The repeatability and reproducibility of measurements were assessed by within-subject standard deviation (Sw), repeatability (2.77 Sw), coefficient of variation (CoV), and intraclass correlation coefficient. RESULTS The TMH measured with the keratograph and FD-OCT was 0.232 ± 0.074 mm and 0.308 ± 0.129 mm, respectively (P < 0.01). A close correlation was found between the TMH measured with the keratograph and FD-OCT (r = 0.343). There was a negative correlation between the mean TMH and differences in the TMH measured with the keratograph and FD-OCT (r = 0.359). Both measurements correlated with the Schirmer test score, tear breakup time, and corneal staining score with P < 0.01. Intraexaminer CoV, 2.77 Sw, and intraclass correlation coefficient of the TMH were <6.5%, <0.059 mm, and >0.986, respectively, and interexaminer CoV and 2.77 Sw were 5.58% and 0.039 mm, respectively. CONCLUSIONS Although the TMH measured with the keratograph tended to be lower than that measured with FD-OCT, the TMH measured with the keratograph closely correlated with the TMH measured with FD-OCT and conventional tests and had good repeatability and reliability.
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Spadea L, Maraone G, Verboschi F, Vingolo EM, Tognetto D. Effect of corneal light scatter on vision: a review of the literature. Int J Ophthalmol 2016; 9:459-64. [PMID: 27158621 DOI: 10.18240/ijo.2016.03.24] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2014] [Accepted: 06/08/2015] [Indexed: 11/23/2022] Open
Abstract
The cornea is the transparent connective tissue window at the front of the eye. The physiological role of the cornea is to conduct external light into the eye, focus it, together with the lens, onto the retina, and to provide rigidity to the entire eyeball. Therefore, good vision requires maintenance of the transparency and proper refractive shape of the cornea. The surface structures irregularities can be associated with wavefront aberrations and scattering errors. Light scattering in the human cornea causes a reduction of visual quality. In fact, the cornea must be transparent and maintain a smooth and stable curvature since it contributes to the major part of the focusing power of the eye. In most cases, a simple examination of visual acuity cannot demonstrate the reduction of visual quality secondary light scattering. In fact, clinical techniques for examining the human cornea in vivo have greatly expanded over the last few decades. The measurement of corneal back scattering qualifies the degree of corneal transparency. The measurement of corneal forward-scattering quantifies the amount of visual impairment that is produced by the alteration of transparency. The aim of this study was to review scattering in the human cornea and methods of measuring it.
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Affiliation(s)
- Leopoldo Spadea
- Department of Biotechnology and Medical-Surgical Sciences, "Sapienza" University of Rome, Latina 04100, Italy
| | - Giorgia Maraone
- Department of Biotechnology and Medical-Surgical Sciences, "Sapienza" University of Rome, Latina 04100, Italy
| | - Francesca Verboschi
- Department of Biotechnology and Medical-Surgical Sciences, "Sapienza" University of Rome, Latina 04100, Italy
| | - Enzo Maria Vingolo
- Department of Biotechnology and Medical-Surgical Sciences, "Sapienza" University of Rome, Latina 04100, Italy
| | - Daniele Tognetto
- Eye Clinic, Ospedale Maggiore, University of Trieste, Trieste 34010, Italy
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Sun M, Pérez-Merino P, Martinez-Enriquez E, Velasco-Ocana M, Marcos S. Full 3-D OCT-based pseudophakic custom computer eye model. BIOMEDICAL OPTICS EXPRESS 2016; 7:1074-88. [PMID: 27231608 PMCID: PMC4866448 DOI: 10.1364/boe.7.001074] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 01/22/2016] [Accepted: 01/27/2016] [Indexed: 05/22/2023]
Abstract
We compared measured wave aberrations in pseudophakic eyes implanted with aspheric intraocular lenses (IOLs) with simulated aberrations from numerical ray tracing on customized computer eye models, built using quantitative 3-D OCT-based patient-specific ocular geometry. Experimental and simulated aberrations show high correlation (R = 0.93; p<0.0001) and similarity (RMS for high order aberrations discrepancies within 23.58%). This study shows that full OCT-based pseudophakic custom computer eye models allow understanding the relative contribution of optical geometrical and surgically-related factors to image quality, and are an excellent tool for characterizing and improving cataract surgery.
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Pérez-Merino P, Velasco-Ocana M, Martinez-Enriquez E, Marcos S. OCT-based crystalline lens topography in accommodating eyes. BIOMEDICAL OPTICS EXPRESS 2015; 6:5039-54. [PMID: 26713216 PMCID: PMC4679276 DOI: 10.1364/boe.6.005039] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 10/22/2015] [Accepted: 10/23/2015] [Indexed: 05/20/2023]
Abstract
Custom 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 best fitting spheres. In the relaxed state, the spherical term accounted for most of the surface irregularity in the anterior lens (47%) and astigmatism (70%) in the posterior lens. However, in accommodated lenses astigmatism was the predominant surface irregularity (90%) in the anterior lens. The RMS of high-order irregularities of the posterior lens surface was statistically significantly higher than that of the anterior lens surface (x2.02, p<0.0001). There was significant negative correlation in vertical coma (Z3 (-1)) and oblique trefoil (Z3 (-3)) between lens surfaces. The astigmatic angle showed high degree of alignment between corneal surfaces, moderate between corneal and anterior lens surface (~27 deg), but differed by ~80 deg between the anterior and posterior lens surfaces (including relative anterior/posterior lens astigmatic angle shifts (10-20 deg).
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Campos-García M, Cossio-Guerrero C, Moreno-Oliva VI, Huerta-Carranza O. Surface shape evaluation with a corneal topographer based on a conical null-screen with a novel radial point distribution. APPLIED OPTICS 2015; 54:5411-5419. [PMID: 26192841 DOI: 10.1364/ao.54.005411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In order to measure the shape of fast convex aspherics, such as the corneal surface of the human eye, we propose the design of a conical null-screen with a radial point distribution (spots similar to ellipses) drawn on it in such a way that its image, which is formed by reflection on the test surface, becomes an exact array of circular spots if the surface is perfect. Any departure from this geometry is indicative of defects on the evaluated surface. We present the target array design and the surface evaluation algorithm. The precision of the test is increased by performing an iterative process to calculate the surface normals, reducing the numerical errors during the integration. We show the applicability of the null-screen based topographer by testing a spherical calibration surface of 7.8 mm radius of curvature and 11 mm in diameter. Here we obtain an rms difference in sagitta between the evaluated surface and the best-fitting sphere less than 1 μm.
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Hua Y, Stojanovic A, Utheim TP, Chen X, Ræder S, Huang J, Wang Q. Keratometric index obtained by Fourier-domain optical coherence tomography. PLoS One 2015; 10:e0122441. [PMID: 25886489 PMCID: PMC4401696 DOI: 10.1371/journal.pone.0122441] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Accepted: 02/21/2015] [Indexed: 11/19/2022] Open
Abstract
PURPOSE To determine the keratometric indices calculated based on parameters obtained by Fourier-domain optical coherence tomography (FD-OCT). METHODS The ratio of anterior corneal curvature to posterior corneal curvature (Ratio) and keratometric index (N) were calculated within central 3 mm zone with the RTVue FD-OCT (RTVue, Optovue, Inc.) in 186 untreated eyes, 60 post-LASIK/PRK eyes, and 39 keratoconus eyes. The total corneal powers were calculated using different keratometric indices: Kcal based on the mean calculated keratometric index, K1.3315 calculated by the keratometric index of 1.3315, and K1.3375 calculated by the keratometric index of 1.3375. In addition, the total corneal powers based on Gaussian optics formula (Kactual) were calculated. RESULTS The means for Ratio in untreated controls, post-LASIK/PRK group and keratoconus group were 1.176 ± 0.022 (95% confidence interval (CI), 1.172-1.179), 1.314 ± 0.042 (95%CI, 1.303-1.325) and 1.229 ± 0.118 (95%CI, 1.191-1.267), respectively. And the mean calculated keratometric index in untreated controls, post-LASIK/PRK group and keratoconus group were 1.3299 ± 0.00085 (95%CI, 1.3272-1.3308), 1.3242 ± 0.00171 (95%CI, 1.3238-1.3246) and 1.3277 ± 0.0046 (95%CI, 1.3263-1.3292), respectively. All the parameters were normally distributed. The differences between Kcal and Kactual, K1.3315 and Kactual, and K1.3375 and Kactual were 0.00 ± 0.11 D, 0.21 ± 0.11 D and 0.99 ± 0.12 D, respectively, in untreated controls; -0.01 ± 0.20 D, 0.85 ± 0.18 D and 1.56 ± 0.16 D, respectively, in post-LASIK/PRK group; and 0.03 ± 0.67 D, 0.56 ± 0.70 D and 1.40 ± 0.76 D, respectively, in keratoconus group. CONCLUSION The calculated keratometric index is negatively related to the ratio of anterior corneal curvature to posterior corneal curvature in untreated, post-LASIK/PRK, and keratoconus eyes, respectively. Using the calculated keratometric index may improve the prediction accuracies of total corneal powers in untreated controls, but not in post-LASIK/PRK and keratoconus eyes.
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Affiliation(s)
- Yanjun Hua
- Department of Ophthalmology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, China
| | - Aleksander Stojanovic
- Department of Ophthalmology, University Hospital of North Norway, Tromsø, Norway
- SynsLaser Kirurgi AS, Tromsø/Oslo, Norway
| | - Tor Paaske Utheim
- Department of Medical Biochemistry, Oslo University Hospital, Oslo, Norway
| | | | - Sten Ræder
- SynsLaser Kirurgi AS, Tromsø/Oslo, Norway
| | - Jinhai Huang
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Key Laboratory of Vision Science, Ministry of Health of People’s Republic of China, Wenzhou, Zhejiang, People’s Republic of China
| | - Qinmei Wang
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Key Laboratory of Vision Science, Ministry of Health of People’s Republic of China, Wenzhou, Zhejiang, People’s Republic of China
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Sun M, Birkenfeld J, de Castro A, Ortiz S, Marcos S. OCT 3-D surface topography of isolated human crystalline lenses. BIOMEDICAL OPTICS EXPRESS 2014; 5:3547-61. [PMID: 25360371 PMCID: PMC4206323 DOI: 10.1364/boe.5.003547] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 08/22/2014] [Accepted: 08/28/2014] [Indexed: 05/23/2023]
Abstract
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 36.5 deg, tended to decrease with age, and was >45 deg in 36.1% lenses. The anterior surface RMS spherical term, RMS coma and 3rd order RMS decreased significantly with age. In general, there was a statistically significant correlation between the 3rd and 4th order terms of the anterior and posterior surfaces. Understanding the coordination of anterior and posterior lens surface geometries and their topographical changes with age sheds light into the role of the lens in the optical properties of the eye and the lens aging mechanism.
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31
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Rüegsegger MB, Geiser D, Steiner P, Pica A, Aebersold DM, Kowal JH. Noninvasive referencing of intraocular tumors for external beam radiation therapy using optical coherence tomography: A proof of concept. Med Phys 2014; 41:081704. [DOI: 10.1118/1.4885975] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Bandlitz S, Purslow C, Murphy PJ, Pult H. Comparison of a new portable digital meniscometer and optical coherence tomography in tear meniscus radius measurement. Acta Ophthalmol 2014; 92:e112-8. [PMID: 24119097 DOI: 10.1111/aos.12275] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 08/22/2013] [Indexed: 11/27/2022]
Abstract
PURPOSE Non-invasive measurement of tear meniscus radius (TMR) is useful in the assessment of tear volume for dry eye diagnosis. This study investigates the agreement between a new, portable, slit-lamp mounted, digital meniscometer (PDM) and optical coherence tomography (OCT) in the measurement of human TMR. METHODS Images of the tear meniscus at the centre of the lower lid of 30 normal subjects (8M, 22F; mean age 27.5 SD ± 9.6 years) were taken using the PDM and the OCT. On the PDM and OCT images, TMR was measured using imagej 1.46b software. The meniscus on the OCT images was subdivided vertically into three equal sections and the radius calculated for each: bottom (BTMR), centre (CTMR) and top (TTMR). The relationship between PDM and OCT measurements was analysed using Spearman's rank coefficient, and differences between PDM and OCT subsection measurements were evaluated using Bland-Altman plots. RESULTS Tear meniscus radius measured with the PDM (0.25 ± 0.06 mm) and OCT (0.29 ± 0.09 mm) was significantly correlated (r = 0.675; p < 0.001). The mean differences between TMR using the PDM and the subsections from OCT showed that TMR measured with PDM was greater for BTMR (0.07 mm; CI 0.05-0.10; p < 0.001), similar for CTMR (-0.01 mm; CI -0.04 to 0.02; p = 0.636) and steeper for TTMR (-0.07 mm; CI -0.10 to -0.04; p < 0.001). CONCLUSIONS Portable digital meniscometer and OCT measurements of the TMR are significantly correlated, suggesting that the new PDM is a useful surrogate for OCT in this respect. The PDM appears to measure the radius of the central section of the tear meniscus.
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Affiliation(s)
- Stefan Bandlitz
- Contact Lens and Anterior Eye Research Group; School of Optometry and Vision Sciences; Cardiff University; Cardiff UK
- Höhere Fachschule für Augenoptik Köln (Cologne School of Optometry); Cologne Germany
| | | | - Paul J. Murphy
- School of Optometry and Vision Science; University of Waterloo; Waterloo Canada
| | - Heiko Pult
- Contact Lens and Anterior Eye Research Group; School of Optometry and Vision Sciences; Cardiff University; Cardiff UK
- Dr. Heiko Pult - Optometry and Vision Research; Weinheim Germany
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33
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Pérez-Merino P, Ortiz S, Alejandre N, de Castro A, Jiménez-Alfaro I, Marcos S. Ocular and optical coherence tomography-based corneal aberrometry in keratoconic eyes treated by intracorneal ring segments. Am J Ophthalmol 2014; 157:116-127.e1. [PMID: 24161248 DOI: 10.1016/j.ajo.2013.08.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 08/20/2013] [Accepted: 08/21/2013] [Indexed: 11/29/2022]
Abstract
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 and posterior corneal surfaces. Total aberrations were measured using a custom-developed laser ray tracing aberrometer. Corneal and total aberrations were compared in 8 eyes pre- and postoperatively for 4-mm pupils. RESULTS Total and corneal aberrations were highly correlated. Average root mean square of corneal and total high-order aberrations (HOAs) were 0.78 ± 0.35 μm and 0.57 ± 0.39 μm preoperatively, and 0.88 ± 0.36 μm and 0.53 ± 0.24 μm postoperatively (4-mm pupils). The anterior corneal surface aberrations were partially compensated by the posterior corneal surface aberrations (by 8.3% preoperatively and 4.1% postoperatively). Astigmatism was 2.03 ± 1.11 μm preoperatively and 1.60 ± 0.94 μm postoperatively. The dominant HOA aberrations both pre- and postoperatively were vertical coma (Z3(-1)), vertical trefoil (Z3(-3)), and secondary astigmatism (Z4(4)). ICRS decreased corneal astigmatism by 27% and corneal coma by 5%, but on average, the overall amount of HOA did not decrease significantly with ICRS treatment. CONCLUSIONS OCT is a reproducible technique to evaluate corneal aberrations. OCT-based corneal aberrations and ocular aberrations show a high correspondence in keratoconic patients before and after ICRS implantation. ICRS produced a decrease in astigmatism, but on average did not produce a consistent decrease of HOAs.
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Affiliation(s)
- Pablo Pérez-Merino
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
| | - Sergio Ortiz
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Nicolas Alejandre
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain; Fundación Jiménez Díaz, Madrid, Spain
| | - Alberto de Castro
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | | | - Susana Marcos
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
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Marcos S, Ortiz S, Pérez-Merino P, Birkenfeld J, Durán S, Jiménez-Alfaro I. Three-Dimensional Evaluation of Accommodating Intraocular Lens Shift and Alignment In Vivo. Ophthalmology 2014; 121:45-55. [DOI: 10.1016/j.ophtha.2013.06.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 06/13/2013] [Accepted: 06/13/2013] [Indexed: 10/26/2022] Open
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Gambra E, Ortiz S, Perez-Merino P, Gora M, Wojtkowski M, Marcos S. Static and dynamic crystalline lens accommodation evaluated using quantitative 3-D OCT. BIOMEDICAL OPTICS EXPRESS 2013; 4:1595-609. [PMID: 24049680 PMCID: PMC3771830 DOI: 10.1364/boe.4.001595] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 07/21/2013] [Accepted: 07/21/2013] [Indexed: 05/24/2023]
Abstract
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 lens thickness were also estimated from dynamic 2-D OCT images (14 Hz), acquired during 5-s of steady fixation, for different accommodative demands. Estimates of the eye power from dynamical geometrical measurements revealed an increase of the fluctuations of the accommodative response from 0.07 D to 0.47 D between 0 and 6 D (0.044 D per D of accommodative demand). A sensitivity analysis showed that the fluctuations of accommodation were driven by dynamic changes in the lens surfaces, particularly in the posterior lens surface.
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Affiliation(s)
- Enrique Gambra
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | - Sergio Ortiz
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | - Pablo Perez-Merino
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | - Michalina Gora
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, ul. Grudziądzka 5/7, PL-87-100 Toruń, Poland
- Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, 50 Blossom Street, Boston, Massachusetts, USA
| | - Maciej Wojtkowski
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, ul. Grudziądzka 5/7, PL-87-100 Toruń, Poland
| | - Susana Marcos
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
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Tao A, Shao Y, Zhong J, Jiang H, Shen M, Wang J. Versatile optical coherence tomography for imaging the human eye. BIOMEDICAL OPTICS EXPRESS 2013; 4:1031-44. [PMID: 23847729 PMCID: PMC3704085 DOI: 10.1364/boe.4.001031] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 05/22/2013] [Accepted: 05/31/2013] [Indexed: 05/04/2023]
Abstract
We demonstrated the feasibility of a CMOS-based spectral domain OCT (SD-OCT) for versatile ophthalmic applications of imaging the corneal epithelium, limbus, ocular surface, contact lens, crystalline lens, retina, and full eye in vivo. The system was based on a single spectrometer and an alternating reference arm with four mirrors. A galvanometer scanner was used to switch the reference beam among the four mirrors, depending on the imaging application. An axial resolution of 7.7 μm in air, a scan depth of up to 37.7 mm in air, and a scan speed of up to 70,000 A-lines per second were achieved. The approach has the capability to provide high-resolution imaging of the corneal epithelium, contact lens, ocular surface, and tear meniscus. Using two reference mirrors, the zero delay lines were alternatively placed on the front cornea or on the back lens. The entire ocular anterior segment was imaged by registering and overlapping the two images. The full eye through the pupil was measured when the reference arm was switched among the four reference mirrors. After mounting a 60 D lens in the sample arm, this SD-OCT was used to image the retina, including the macula and optical nerve head. This system demonstrates versatility and simplicity for multi-purpose ophthalmic applications.
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Affiliation(s)
- Aizhu Tao
- Bascom Palmer Eye Institute, University of Miami, Miami, FL 33136, USA
- School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, Zhejiang 325027, China
| | - Yilei Shao
- Bascom Palmer Eye Institute, University of Miami, Miami, FL 33136, USA
- School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, Zhejiang 325027, China
| | - Jianguang Zhong
- Bascom Palmer Eye Institute, University of Miami, Miami, FL 33136, USA
- Hangzhou First People's Hospital, Hangzhou, Zhejiang 310006, China
| | - Hong Jiang
- Bascom Palmer Eye Institute, University of Miami, Miami, FL 33136, USA
| | - Meixiao Shen
- School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, Zhejiang 325027, China
| | - Jianhua Wang
- Bascom Palmer Eye Institute, University of Miami, Miami, FL 33136, USA
- Electrical and Computer Engineering, University of Miami, Miami, FL 33136, USA
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McNabb RP, Kuo AN, Izatt JA. Quantitative single and multi-surface clinical corneal topography utilizing optical coherence tomography. OPTICS LETTERS 2013; 38:1212-1214. [PMID: 23595434 PMCID: PMC4517424 DOI: 10.1364/ol.38.001212] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Successful surgical treatment of ocular astigmatism requires accurate characterization of both magnitude and axis of the astigmatism. Keratometry and topography are clinically widely used for this measurement; however, their analysis is limited to the anterior corneal surface. Unlike these techniques, optical coherence tomography (OCT) offers the advantage of measuring both the anterior and posterior corneal surface contributions. We present a technique to combine the local curvatures of both surfaces into a single pseudosurface suitable for clinical application. Building on prior work in distributed scanning OCT (DSOCT) to remove corrupting patient motion artifacts, we present the results of a pilot patient study where extracted values of clinical corneal astigmatic power magnitude and direction from DSOCT corneal volumes were comparable to standard clinical measures of corneal astigmatism.
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Affiliation(s)
- Ryan P McNabb
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, North Carolina 27708, USA.
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Ortiz S, Pérez-Merino P, Durán S, Velasco-Ocana M, Birkenfeld J, de Castro A, Jiménez-Alfaro I, Marcos S. Full OCT anterior segment biometry: an application in cataract surgery. BIOMEDICAL OPTICS EXPRESS 2013; 4:387-96. [PMID: 23503926 PMCID: PMC3595049 DOI: 10.1364/boe.4.000387] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 12/26/2012] [Accepted: 01/03/2013] [Indexed: 05/17/2023]
Abstract
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, CLT/ILT Tilt and decentration are retrieved with a very high degree of accuracy. IOL was placed 400 μm behind the natural crystalline lens, The IOL was aligned with a similar orientation of the natural lens (2.47 deg superiorly), but slightly lower amounts (0.77 deg superiorly). The IOL was decentered superiorly (0.39 mm) and nasally (0.26 mm).
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Affiliation(s)
- Sergio Ortiz
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | - Pablo Pérez-Merino
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | - Sonia Durán
- Fundación Jiménez-Díaz, Avda. Reyes Católicos, 2, 28040, Madrid, Spain
| | - Miriam Velasco-Ocana
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | - Judith Birkenfeld
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | - Alberto de Castro
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | | | - Susana Marcos
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
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39
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Distortion correction of OCT images of the crystalline lens: gradient index approach. Optom Vis Sci 2012; 89:E709-18. [PMID: 22466105 DOI: 10.1097/opx.0b013e3182508344] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
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 vitro) and compared with the performance of two other existing methods (simple division, refraction correction: assuming a homogeneous index). Comparisons were made in terms of posterior surface radius, conic constant, root mean square, peak to valley, and lens thickness shifts from the nominal data. RESULTS Differences in the retrieved radius and conic constant were not statistically significant across methods. However, GRIN distortion correction with optimal shape GRIN parameters provided more accurate estimates of the posterior lens surface in terms of root mean square and peak values, with errors <6 and 13 μm, respectively, on average. Thickness was also more accurately estimated with the new method, with a mean discrepancy of 8 μm. CONCLUSIONS The posterior surface of the crystalline lens and lens thickness can be accurately reconstructed from OCT images, with the accuracy improving with an accurate model of the GRIN distribution. The algorithm can be used to improve quantitative knowledge of the crystalline lens from OCT imaging in vivo. Although the improvements over other methods are modest in two dimension, it is expected that three-dimensional imaging will fully exploit the potential of the technique. The method will also benefit from increasing experimental data of GRIN distribution in the lens of larger populations.
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40
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Ortiz S, Pérez-Merino P, Gambra E, de Castro A, Marcos S. In vivo human crystalline lens topography. BIOMEDICAL OPTICS EXPRESS 2012; 3:2471-88. [PMID: 23082289 PMCID: PMC3470006 DOI: 10.1364/boe.3.002471] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 07/26/2012] [Accepted: 08/24/2012] [Indexed: 05/24/2023]
Abstract
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 the posterior lens radius by more than 65%. In vivo lens surfaces were fitted by biconicoids and Zernike polynomials after distortion correction. The anterior lens radii of curvature ranged from 10.27 to 14.14 mm, and the posterior lens radii of curvature ranged from 6.12 to 7.54 mm. Surface asphericities ranged from -0.04 to -1.96. The lens surfaces were well fitted by quadrics (with variation smaller than 2%, for 5-mm pupils), with low amounts of high order terms. Surface lens astigmatism was significant, with the anterior lens typically showing horizontal astigmatism ([Formula: see text] ranging from -11 to -1 µm) and the posterior lens showing vertical astigmatism ([Formula: see text] ranging from 6 to 10 µm).
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Affiliation(s)
- Sergio Ortiz
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid,
Spain
| | - Pablo Pérez-Merino
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid,
Spain
| | - Enrique Gambra
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid,
Spain
| | - Alberto de Castro
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid,
Spain
| | - Susana Marcos
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid,
Spain
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41
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McNabb RP, LaRocca F, Farsiu S, Kuo AN, Izatt JA. Distributed scanning volumetric SDOCT for motion corrected corneal biometry. BIOMEDICAL OPTICS EXPRESS 2012; 3:2050-2065. [PMID: 23024900 PMCID: PMC3447548 DOI: 10.1364/boe.3.002050] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Revised: 08/08/2012] [Accepted: 08/09/2012] [Indexed: 05/29/2023]
Abstract
We present a method, termed distributed scanning OCT (DSOCT), which reduces the effects of patient motion on corneal biometry utilizing current-generation clinically available spectral domain optical coherence tomography (SDOCT) systems. We first performed a pilot study of the power spectrum of normal patient axial eye motion based on repeated (M-mode) SDOCT. Using DSOCT to reduce the effects of patient motion, we conducted a preliminary patient study comparing the measured anterior and posterior corneal curvatures and the calculated corneal power to both corneal topography and Scheimpflug photography in normal subjects. The repeatability for the measured radius of curvature of both anterior and posterior surfaces as well as calculated corneal refractive power using DSOCT was comparable to those of both topography and Scheimpflug photography.
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Affiliation(s)
- Ryan P. McNabb
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
| | - Francesco LaRocca
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
| | - Sina Farsiu
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
- Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
| | - Anthony N. Kuo
- Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
| | - Joseph A. Izatt
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
- Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
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Yasumatsu N, Watanabe S. T-ray topography by time-domain polarimetry. OPTICS LETTERS 2012; 37:2706-2708. [PMID: 22743502 DOI: 10.1364/ol.37.002706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We demonstrate a method for substantially improving the axial resolution of terahertz time-of-flight measurements by analyzing the time-dependent polarization direction of an elliptically polarized single-cycle terahertz electromagnetic (T-ray) pulse. We show that, at its most sensitive, the technique has an axial resolution of ∼λ/1000 (<1 μm) with a subsecond measurement time, and very clear T-ray topographic images are obtained. Such a very high axial resolution of the T-ray topography opens the way for novel industrial and biomedical applications such as fine metalworking and corneal inspection in a safe manner.
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Affiliation(s)
- Naoya Yasumatsu
- Department of Physics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522, Japan
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43
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Kuo AN, McNabb RP, Zhao M, LaRocca F, Stinnett SS, Farsiu S, Izatt JA. Corneal biometry from volumetric SDOCT and comparison with existing clinical modalities. BIOMEDICAL OPTICS EXPRESS 2012; 3:1279-90. [PMID: 22741075 PMCID: PMC3370969 DOI: 10.1364/boe.3.001279] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 05/04/2012] [Accepted: 05/04/2012] [Indexed: 05/22/2023]
Abstract
We present a comparison of corneal biometric values from dense volumetric spectral domain optical coherence tomography (SDOCT) scans to reference values in both phantoms and clinical subjects. We also present a new optically based "keratometric equivalent power" formula for SDOCT that eliminates previously described discrepancies between corneal power form SDOCT and existing clinical modalities. Phantom objects of varying radii of curvature and corneas of normal subjects were imaged with a clinical SDOCT system. The optically corrected three-dimensional surfaces were used to recover radii of curvature and power as appropriate. These were then compared to the manufacturer's reference values in phantoms and to measurements from topography and Scheimpflug photography in subjects. In phantom objects, paired differences between SDOCT and reference values for radii of curvature were not statistically significant. In subjects, there were no significant paired differences between SDOCT and reference values from the other modalities for anterior radius and corneal keratometric power. In contrast to other studies, we found that dense volumetric scans with available SDOCT can be used to recover corneal biometric values-including power-that correspond well with existing clinical measurements.
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Affiliation(s)
- Anthony N. Kuo
- Department of Ophthalmology, Duke University Medical Center, Durham NC 27710, USA
| | - Ryan P. McNabb
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham NC 27708, USA
| | - Mingtao Zhao
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham NC 27708, USA
| | - Francesco LaRocca
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham NC 27708, USA
| | - Sandra S. Stinnett
- Department of Ophthalmology, Duke University Medical Center, Durham NC 27710, USA
- Department of Biostatistics and Bioinformatics, Duke University Medical Center, Durham NC 27710, USA
| | - Sina Farsiu
- Department of Ophthalmology, Duke University Medical Center, Durham NC 27710, USA
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham NC 27708, USA
| | - Joseph A. Izatt
- Department of Ophthalmology, Duke University Medical Center, Durham NC 27710, USA
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham NC 27708, USA
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Ortiz S, Pérez-Merino P, Alejandre N, Gambra E, Jimenez-Alfaro I, Marcos S. Quantitative OCT-based corneal topography in keratoconus with intracorneal ring segments. BIOMEDICAL OPTICS EXPRESS 2012; 3:814-24. [PMID: 22567577 PMCID: PMC3342189 DOI: 10.1364/boe.3.000814] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 03/16/2012] [Accepted: 03/21/2012] [Indexed: 05/19/2023]
Abstract
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 maps (fitted by biconicoids and Zernike polynomials) and pachymetry. Automatic tools were developed for the estimation of the 3-D positioning of the ICRS. The pupil center reference was estimated from the segmented iris volume. The developed algorithms are illustrated in a keratoconic eye (grade III) pre- and 30 days post-operatively after implantation of two triangular-section, 0.3-mm thick Ferrara ring segments. Quantitative corneal topographies reveal that the ICRS produced a flattening of the anterior surface, a steepening of the posterior surface, meridional differences in the changes in curvature and asphericity, and increased symmetry of the anterior topography. Optical distortion correction through the ICRS (of a different refractive index from the cornea) allowed accurate pachymetric estimates, which showed increased thickness in the ectatic area as well as in peripheral corneal areas. Automatic tools allowed estimation of the depth of the implanted ICRS ring, as well as its rotation with respect to the pupil plane. Anterior segment sOCT provided with fan and optical distortion correction and analysis tools is an excellent instrument for evaluating and monitoring keratoconic eyes and for the quantification of the changes produced by ICRS treatment.
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Affiliation(s)
- Sergio Ortiz
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | - Pablo Pérez-Merino
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | - Nicolas Alejandre
- Fundación Jiménez-Díaz, Avda. Reyes Católicos, 2, 28040, Madrid, Spain
| | - E. Gambra
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
| | - I. Jimenez-Alfaro
- Fundación Jiménez-Díaz, Avda. Reyes Católicos, 2, 28040, Madrid, Spain
| | - Susana Marcos
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain
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