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Article ; Online: Estimation of Crystalline Lens Material Properties From Patient Accommodation Data and Finite Element Models.

de la Hoz, Andres / Martinez-Enriquez, Eduardo / Marcos, Susana

Investigative ophthalmology & visual science

2024 Volume 64, Issue 11, Page(s) 31

Abstract: Purpose: The mechanical properties of the crystalline lens are related to its optical function of accommodation, and their changes with age are one of the potential causes for presbyopia. We estimated the mechanical parameters of the crystalline lens ... ...

Abstract	Purpose: The mechanical properties of the crystalline lens are related to its optical function of accommodation, and their changes with age are one of the potential causes for presbyopia. We estimated the mechanical parameters of the crystalline lens using quantitative optical coherence tomography (OCT) imaging and wavefront sensing data from accommodating participants and computer modeling. Methods: Full-lens shape data (from quantitative swept-source OCT and eigenlens representation) and optical power data (from Hartmann-Shack wavefront sensor) were obtained from 11 participants (22-30 years old) for relaxed accommodation at infinity and -4.5 D accommodative demand. Finite element models of lens, capsular bag, zonulae, and ciliary body were constructed using measured lens geometry and literature data, assuming a 60-mN radial force. An inverse modeling scheme was used to determine the shear moduli of the nucleus and cortex of the lens, such that the simulated deformed (maximally stretched) lens matched the participant's lens at -4.5 D. Results: The shear moduli of the nucleus and cortex were 1.62 ± 1.32 and 8.18 ± 5.63 kPa, on average, respectively. The shear modulus of the nucleus was lower than that of the cortex for all participants evaluated. The average of the two moduli per participant was statistically significantly correlated with age (R2 = 0.76, P = 0.0049). Conclusions: In vivo imaging and mechanical modeling of the crystalline lens allow estimations of the crystalline lens' mechanical properties. Differences between nuclear and cortical moduli and their dependency with age appear to be critical in accommodative function and likely in its impairment in presbyopia.
MeSH term(s)	Humans ; Male ; Female ; Lens, Crystalline/diagnostic imaging ; Accommodation, Ocular ; Finite Element Analysis ; Presbyopia ; Tomography, Optical Coherence/methods ; Computer Simulation ; Healthy Volunteers ; Adult
Language	English
Publishing date	2024-02-19
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
ZDB-ID	391794-0
ISSN	1552-5783 ; 0146-0404
ISSN (online)	1552-5783
ISSN	0146-0404
DOI	10.1167/iovs.64.11.31
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article: Effect of fixational eye movements in corneal topography measurements with optical coherence tomography.

de Castro, Alberto / Martínez-Enríquez, Eduardo / Marcos, Susana

Biomedical optics express

2023 Volume 14, Issue 5, Page(s) 2138–2152

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 ... ...

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.
Language	English
Publishing date	2023-04-21
Publishing country	United States
Document type	Journal Article
ZDB-ID	2572216-5
ISSN	2156-7085
ISSN	2156-7085
DOI	10.1364/BOE.486460
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Book ; Online: Deterministic Decoupling of Global Features and its Application to Data Analysis

Martinez-Enriquez, Eduardo / Gonzalez, Maria del Mar / Portilla, Javier

2022

Abstract: We introduce a method for deterministic decoupling of global features and show its applicability to improve data analysis performance, as well as to open new venues for feature transfer. We propose a new formalism that is based on defining ... ...

Abstract	We introduce a method for deterministic decoupling of global features and show its applicability to improve data analysis performance, as well as to open new venues for feature transfer. We propose a new formalism that is based on defining transformations on submanifolds, by following trajectories along the features gradients. Through these transformations we define a normalization that, we demonstrate, allows for decoupling differentiable features. By applying this to sampling moments, we obtain a quasi-analytic solution for the orthokurtosis, a normalized version of the kurtosis that is not just decoupled from mean and variance, but also from skewness. We apply this method in the original data domain and at the output of a filter bank to regression and classification problems based on global descriptors, obtaining a consistent and significant improvement in performance as compared to using classical (non-decoupled) descriptors. Comment: 29 pages, 12 figures
Keywords	Computer Science - Machine Learning ; I.4.7 ; I.5.1
Publishing date	2022-07-05
Publishing country	us
Document type	Book ; Online
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Article: Eigenlenses

Martinez-Enriquez, Eduardo / de Castro, Alberto / Marcos, Susana

Biomedical optics express

2020 Volume 11, Issue 10, Page(s) 5633–5649

Abstract: The crystalline lens is an important optical element in the eye, responsible for focusing, and which experiences significant changes throughout life. The shape of the lens is usually studied only in the optical area (central 4 to 6 mm). However, for a ... ...

Abstract	The crystalline lens is an important optical element in the eye, responsible for focusing, and which experiences significant changes throughout life. The shape of the lens is usually studied only in the optical area (central 4 to 6 mm). However, for a great number of applications, a description of the full shape of the crystalline lens is required. We propose a new method for the representation of the full shape of the crystalline lens, constructed from 3-dimensional optical coherence tomography images of 133 isolated crystalline lenses (0-71 y/o), which we have called
Language	English
Publishing date	2020-09-16
Publishing country	United States
Document type	Journal Article
ZDB-ID	2572216-5
ISSN	2156-7085
ISSN	2156-7085
DOI	10.1364/BOE.397695
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Article: Estimation of the full shape of the crystalline lens from OCT: validation using stretched donor lenses.

Martínez-Enríquez, Eduardo / Maceo Heilman, Bianca / de Castro, Alberto / Mohamed, Ashik / Ruggeri, Marco / Zvietcovich, Fernando / Manns, Fabrice / Marcos, Susana

Biomedical optics express

2023 Volume 14, Issue 8, Page(s) 4261–4276

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 ... ...

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
Language	English
Publishing date	2023-07-25
Publishing country	United States
Document type	Journal Article
ZDB-ID	2572216-5
ISSN	2156-7085
ISSN	2156-7085
DOI	10.1364/BOE.493795
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Article: Quantization of collagen organization in the stroma with a new order coefficient.

Germann, James A / Martinez-Enriquez, Eduardo / Marcos, Susana

Biomedical optics express

2017 Volume 9, Issue 1, Page(s) 173–189

Abstract: Many optical and biomechanical properties of the cornea, specifically the transparency of the stroma and its stiffness, can be traced to the degree of order and direction of the constituent collagen fibers. To measure the degree of order inside the ... ...

Abstract	Many optical and biomechanical properties of the cornea, specifically the transparency of the stroma and its stiffness, can be traced to the degree of order and direction of the constituent collagen fibers. To measure the degree of order inside the cornea, a new metric, the order coefficient, was introduced to quantify the organization of the collagen fibers from images of the stroma produced with a custom-developed second harmonic generation microscope. The order coefficient method gave a quantitative assessment of the differences in stromal collagen arrangement across the cornea depths and between untreated stroma and cross-linked stroma.
Language	English
Publishing date	2017-12-08
Publishing country	United States
Document type	Journal Article
ZDB-ID	2572216-5
ISSN	2156-7085
ISSN	2156-7085
DOI	10.1364/BOE.9.000173
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Article ; Online: Poster Session: Estimation of scleral biomechanical properties from air-puff-coupled optical coherence tomography.

Birkenfeld, Judith S / Villegas, Lupe / de la Hoz, Andrés / Bronte-Ciriza, David / Varea, Alejandra / Martínez-Enríquez, Eduardo / Curatolo, Andrea / Germann, James A / Marcos, Susana

Journal of vision

2023 Volume 23, Issue 11, Page(s) 38

Abstract: Progression of myopia is usually accompanied by axial overgrowth of the eyeball, which affects scleral biomechanics (BM). To study scleral biomechanics, we propose the use of air-puff deformation swept-source OCT imaging. Air-puff deformation imaging was ...

Abstract	Progression of myopia is usually accompanied by axial overgrowth of the eyeball, which affects scleral biomechanics (BM). To study scleral biomechanics, we propose the use of air-puff deformation swept-source OCT imaging. Air-puff deformation imaging was performed at different sites of ex vivo porcine (n=5) and rabbit (n=3) eyes, (<24hr postmortem): Nasal/temporal equatorial and posterior sclera (NE, NP, TE, TP), superior (S) and inferior (I) sclera, and cornea (C). Intraocular pressure was kept at 15mmHg. Deformation data were used as input to inverse finite element model (FEM) algorithms to reconstruct BM properties. Experimental deformation amplitudes showed dependence on the animal model, with porcine scleras exhibiting greater inter-site variation (displacement of S, I was up to four times greater than that of N, T), while rabbit scleras exhibited at most 40% of displacement differences between all sites. Both models showed significant (p<.001) differences in the temporal deformation profile between sclera and (C), but similarities in all scleral locations, suggesting that the scleral temporal profile is independent of scleral thickness variations. The FEM estimated an elastic modulus of 1.84 ± 0.30 MPa (I) to 6.04 ± 2.11 MPa (TE) for the porcine sclera. The use of scleral air-puff imaging is promising for noninvasive investigation of structural changes in the sclera associated with myopia and for monitoring possible modulation of scleral stiffness with myopia treatment.
MeSH term(s)	Animals ; Rabbits ; Swine ; Tomography, Optical Coherence ; Sclera/diagnostic imaging ; Algorithms ; Biomechanical Phenomena ; Myopia/diagnostic imaging
Language	English
Publishing date	2023-09-21
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
ZDB-ID	2106064-2
ISSN	1534-7362 ; 1534-7362
ISSN (online)	1534-7362
ISSN	1534-7362
DOI	10.1167/jov.23.11.38
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Article ; Online: Corneal Collagen Ordering After In Vivo Rose Bengal and Riboflavin Cross-Linking.

Germann, James A / Martínez-Enríquez, Eduardo / Martínez-García, M Carmen / Kochevar, Irene E / Marcos, Susana

Investigative ophthalmology & visual science

2020 Volume 61, Issue 3, Page(s) 28

Abstract: Purpose: Photoactivated cornea collagen cross-linking (CXL) increases corneal stiffness by initiating formation of covalent bonds between stromal proteins. Because CXL depends on diffusion to distribute the photoinitiator, a gradient of CXL efficiency ... ...

Abstract	Purpose: Photoactivated cornea collagen cross-linking (CXL) increases corneal stiffness by initiating formation of covalent bonds between stromal proteins. Because CXL depends on diffusion to distribute the photoinitiator, a gradient of CXL efficiency with depth is expected that may affect the degree of stromal collagen organization. We used second harmonic generation (SHG) microscopy to investigate the differences in stromal collagen organization in rabbit eyes after corneal CXL in vivo as a function of depth and time after surgery. Methods: Rabbit corneas were treated in vivo with either riboflavin/UV radiation (UVX) or Rose Bengal/green light (RGX) and evaluated 1 and 2 months after CXL. Collagen fibers were imaged with a custom-built SHG scanning microscope through the central cornea (350 µm depth, 225 × 225 µm en face images). The order coefficient (OC), a metric for collagen organization, and total SHG signal were computed for each depth and compared between treatments. Results: OC values of CXL-treated corneas were larger than untreated corneas by 27% and 20% after 1 month and 38% and 33% after 2 months for the RGX and UVX, respectively. RGX OC values were larger than UVX OC values by 3% and 5% at 1 and 2 months. The SHG signal was higher in CXL corneas than untreated corneas, both at 1 and 2 months after surgery, by 18% and 26% and 1% and 10% for RGX and UVX, respectively. Conclusions: Increased OC corresponded with increased collagen fiber organization in CXL corneas. Changes in collagen organization parallel reported temporal changes in cornea stiffness after CXL and also, surprisingly, are detected deeper in the stroma than the regions stiffened by collagen cross-links.
MeSH term(s)	Animals ; Collagen/metabolism ; Corneal Stroma/drug effects ; Corneal Stroma/metabolism ; Corneal Stroma/pathology ; Cross-Linking Reagents ; Female ; Fluorescent Dyes/pharmacology ; Microscopy ; Photosensitizing Agents/pharmacology ; Rabbits ; Riboflavin/pharmacology ; Rose Bengal/pharmacology ; Ultraviolet Rays
Chemical Substances	Cross-Linking Reagents ; Fluorescent Dyes ; Photosensitizing Agents ; Rose Bengal (1ZPG1ELY14) ; Collagen (9007-34-5) ; Riboflavin (TLM2976OFR)
Language	English
Publishing date	2020-03-10
Publishing country	United States
Document type	Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	391794-0
ISSN	1552-5783 ; 0146-0404
ISSN (online)	1552-5783
ISSN	0146-0404
DOI	10.1167/iovs.61.3.28
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Article: Estimation of the full shape of the crystalline lens

Martínez-Enríquez, Eduardo / Curatolo, Andrea / de Castro, Alberto / Birkenfeld, Judith S / González, Ana M / Mohamed, Ashik / Ruggeri, Marco / Manns, Fabrice / Fernando, Zvietcovich / Marcos, Susana

Biomedical optics express

2023 Volume 14, Issue 2, Page(s) 608–626

Abstract: Quantifying the full 3-D shape of the human crystalline lens is important for improving intraocular lens power or sizing calculations in treatments of cataract and presbyopia. In a previous work we described a novel method for the representation of the ... ...

Abstract	Quantifying the full 3-D shape of the human crystalline lens is important for improving intraocular lens power or sizing calculations in treatments of cataract and presbyopia. In a previous work we described a novel method for the representation of the full shape of the
Language	English
Publishing date	2023-01-05
Publishing country	United States
Document type	Journal Article
ZDB-ID	2572216-5
ISSN	2156-7085
ISSN	2156-7085
DOI	10.1364/BOE.477557
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Article ; Online: Simulating Outcomes of Cataract Surgery: Important Advances in Ophthalmology.

Marcos, Susana / Martinez-Enriquez, Eduardo / Vinas, Maria / de Castro, Alberto / Dorronsoro, Carlos / Bang, Seung Pil / Yoon, Geunyoung / Artal, Pablo

Annual review of biomedical engineering

2021 Volume 23, Page(s) 277–306

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 ...

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.
MeSH term(s)	Cataract ; Humans ; Lens Implantation, Intraocular ; Lens, Crystalline ; Ophthalmology ; Prospective Studies
Language	English
Publishing date	2021-04-13
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
ZDB-ID	1448425-0
ISSN	1545-4274 ; 1523-9829
ISSN (online)	1545-4274
ISSN	1523-9829
DOI	10.1146/annurev-bioeng-082420-035827
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