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

Castro, Alberto de; Birkenfeld, Judith; Heilman, Bianca Maceo; Ruggeri, Marco; Arrieta, Esdras; Parel, Jean Marie; Manns, Fabrice; Marcos, Susana

doi:10.1364/boe.10.003622

Cited by 4 publications

(2 citation statements)

References 43 publications

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“…Whether the guinea pig lens can accommodate or not is a matter of debate, and therefore we do not know if geometrical differences are expected between the in vivo and in vitro (nominally maximally accommodated) conditions. In any case, we do not expect this fact to affect the estimated GRIN parameters, as a previous study did not show significant differences in nucleus or surface refractive indices or shape factor with accommodation in cynomolgus monkey lenses mounted in a stretcher …”

Section: Discussionmentioning

confidence: 80%

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Crystalline lens gradient refractive index distribution in the guinea pig

Castro

Martinez-Enriquez

Pérez-Merino

et al. 2020

Ophthalmic Physiologic Optic

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Purpose: The crystalline lens undergoes morphological and functional changes with age and may also play a role in eye emmetropisation. Both the geometry and the gradient index of refraction (GRIN) distribution contribute to the lens optical properties. We studied the lens GRIN in the guinea pig, a common animal model to study myopia. Methods: Lenses were extracted from guinea pigs (Cavia porcellus) at 18 days of age (n = 4, three monolaterally treated with negative lenses and one untreated) and 39 days of age (n = 4, all untreated). Treated eyes were myopic (À2.07 D on average) and untreated eyes hyperopic (+3.3 D), as revealed using streak retinoscopy in the live cyclopeged animals. A custom 3D spectral domain optical coherence tomography (OCT) system (k = 840 nm, Dk = 50 nm) was used to image the enucleated crystalline lens at two orientations. Custom algorithms were used to estimate the lens shape and GRIN was modelled with four variables that were reconstructed using the OCT data and a minimisation algorithm. Ray tracing was used to calculate the optical power and spherical aberration assuming a homogeneous refractive index or the estimated GRIN. Results: Guinea pig lenses exhibited nearly parabolic GRIN profiles. When comparing the two age groups (18-and 39 day-old) there was a significant increase in the central thickness (from 3.61 to 3.74 mm), and in the refractive index of the surface (from 1.362 to 1.366) and the nucleus (from 1.443 to 1.454). The presence of GRIN shifted the spherical aberration (À4.1 µm on average) of the lens towards negative values. Conclusions: The guinea pig lens exhibits a GRIN profile with surface and nucleus refractive indices that increase slightly during the first weeks of life. GRIN plays a major role in the lens optical properties and should be incorporated into computational guinea pig eye models to study emmetropisation, myopia development and ageing.

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Section: Discussionmentioning

confidence: 80%

“…Essentially, a global optimisation technique is used to optimise the value of the variables of a GRIN model so that the simulated optical path matches the one measured from the OCT images. We have demonstrated the technique in an isolated porcine crystalline lens, in cynomolgus monkey lenses, and in human lenses of different ages …”

Section: Introductionmentioning

confidence: 99%

Crystalline lens gradient refractive index distribution in the guinea pig

Castro

Martinez-Enriquez

Pérez-Merino

et al. 2020

Ophthalmic Physiologic Optic

Self Cite

View full text Add to dashboard Cite

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Age-related changes in geometry and transparency of human crystalline lens revealed by optical signal discontinuity zones in swept-source OCT images

Gupta,

Ruminski,

Villar

et al. 2023

Eye and Vis

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Background The shape and microstructure of the human crystalline lens alter with ageing, and this has an effect on the optical properties of the eye. The aim of this study was to characterise the age-related differences in the morphology and transparency of the eye lenses of healthy subjects through the optical signal discontinuity (OSD) zones in optical coherence tomography (OCT) images. We also investigated the association of those changes with the optical quality of the eye and visual function. Methods OCT images of the anterior segment of 49 eyes of subjects (9–78 years) were acquired, and the OSD zones (nucleus, C1–C4 cortical zones) were identified. Central thickness, curvature and optical density were measured. The eye’s optical quality was evaluated by the objective scatter index (OSI). Contrast sensitivity and visual acuity tests were performed. The correlation between extracted parameters and age was assessed. Results The increase in lens thickness with age was dominated by the thickening of the cortical zone C3 (0.0146 mm/year). The curvature radii of the anterior lens surface and both anterior and posterior nucleo-cortical interfaces decreased with age (− 0.053 mm/year, − 0.013 mm/year and − 0.006 mm/year, respectively), and no change was observed for the posterior lens radius. OCT-based densitometry revealed significant correlations with age for all zones except for C1β, and the highest increase in density was in the C2–C4 zones (R = 0.45, 0.74, 0.56, respectively, P < 0.001). Increase in OSI was associated with the degradation of visual function. Conclusions OCT enables the identification of OSD zones of the crystalline lens. The most significant age-related changes occur in the C3 zone as it thickens with age at a faster rate and becomes more opaque than other OSD zones. The changes are associated with optical quality deterioration and reduction of visual performance. These findings contribute to a better understanding of the structure–function relationship of the ageing lens and offer insights into both pathological and aging alterations.

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Single function crystalline lens capable of mimicking ciliary body accommodation

Jaimes-Nájera¹,

Gómez-Correa²,

Coello³

et al. 2020

Biomed. Opt. Express

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The lens is a complex optical component of the human eye because of its physiological structure: the surface is aspherical and the structural entities create a gradient refractive index (GRIN). Most existent models of the lens deal with its external shape independently of the refractive index and, subsequently, through optimization processes, adjust the imaging properties. In this paper, we propose a physiologically realistic GRIN model of the lens based on a single function for the whole lens that accurately describes different accommodative states simultaneously providing the corresponding refractive index distribution and the external shape of the lens by changing a single parameter that we associate with the function of the ciliary body. This simple, but highly accurate model, is incorporated into a schematic eye constructed with reported experimental biometric data and accommodation is simulated over a range of 0 to 6 diopters to select the optimum levels of image quality. Changes with accommodation in equatorial and total axial lens thicknesses, as well as aberrations, are found to lie within reported biometric data ranges.

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

Cited by 4 publications

References 43 publications

Crystalline lens gradient refractive index distribution in the guinea pig

Crystalline lens gradient refractive index distribution in the guinea pig

Age-related changes in geometry and transparency of human crystalline lens revealed by optical signal discontinuity zones in swept-source OCT images

Single function crystalline lens capable of mimicking ciliary body accommodation

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