The theory and implications of the biaxial model of corneal birefringence

Misson, Gary P.

doi:10.1111/j.1475-1313.2010.00782.x

Cited by 14 publications

(11 citation statements)

References 51 publications

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“…2 The stroma, which makes up around 95% of the cornea, consists of around 300 layers of collagen fibres in the centre, increasing to around 500 layers in the limbal region. 3,4 A number of models of fibril orientation have been proposed. [5][6][7][8][9][10] Fibril size and spacing change from the prepupillary area to the periphery of the cornea.…”

Section: Introductionmentioning

confidence: 99%

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Comparative analysis of the corneal birefringence pattern in healthy children and adults

Sobczak

Asejczyk-Widlicka

Kalinowski

et al. 2021

Ophthalmic Physiologic Optic

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Purpose: To undertake a comparative analysis of the corneal shape, thickness and isochromatics in the eyes of children and adults in order to determine the extent of similarities and differences between the cohorts. Methods: The study involved 24 children (aged 8 years) and 37 young White adults (aged between 22-24 years) with no apparent or known health or ocular conditions. Measurements were made of corneal radius of curvature, both central (CCT) and paracentral (PCT) corneal thickness and intraocular pressure (IOP). Images of the isochromatics were captured using a slit lamp and a circular polarizer. The geometry of fringe I and II of the isochromatics was analysed. Results: Statistically significant differences were found between CCT and PCT in nasal and temporal regions for both the children and adult cohorts. The same trends were observed in the radii of the cornea. Statistically significant differences between side lengths and angles of isochromatic fringes were found. No differences in asymmetry of shape for fringe I between adults and children were detected; greater symmetry was seen in fringe II in children than for adults. Conclusions: The asymmetry in corneal shape and curvature contributes to the shape of the isochromatic fringes. This is likely linked to the orientation and parameters of the collagen fibres and to the muscles' forces, and be relevant for surgical procedures such as corneal transplantation.

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Section: Introductionmentioning

confidence: 99%

“…The cornea is flattest nasally and steepest in the temporal zone 2 . The stroma, which makes up around 95% of the cornea, consists of around 300 layers of collagen fibres in the centre, increasing to around 500 layers in the limbal region 3,4 . A number of models of fibril orientation have been proposed 5–10 .…”

Section: Introductionmentioning

confidence: 99%

Comparative analysis of the corneal birefringence pattern in healthy children and adults

Sobczak

Asejczyk-Widlicka

Kalinowski

et al. 2021

Ophthalmic Physiologic Optic

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“…Intrinsic birefringence has its origin in the optical anisotropy within the collagen fibers, 35,37 which are composed predominately of type I collagen molecules that are known to exhibit positive uniaxial birefringence. 38 The ordered arrangement of the fibers within individual lamellae, embedded in an isotropic ground substance of different refractive index, produces corneal "form" birefringence, 37 and accounts for more than two-thirds of the total corneal birefringence. 38 Each lamella may be considered as a birefringent plate or linear retarder with its axis of birefringence (slow axis) lying along the direction of the collagen fibers, leading to the simplified consideration of the corneal stroma as a series of stacked birefringent plates, with their slow axes lying at various angles to one another.…”

Section: Polarization Properties Of the Central Corneamentioning

confidence: 99%

“…38 The ordered arrangement of the fibers within individual lamellae, embedded in an isotropic ground substance of different refractive index, produces corneal "form" birefringence, 37 and accounts for more than two-thirds of the total corneal birefringence. 38 Each lamella may be considered as a birefringent plate or linear retarder with its axis of birefringence (slow axis) lying along the direction of the collagen fibers, leading to the simplified consideration of the corneal stroma as a series of stacked birefringent plates, with their slow axes lying at various angles to one another. 33,39 A slight prevalence of one lamella orientation results in a net amount and axis of birefringence.…”

Section: Polarization Properties Of the Central Corneamentioning

confidence: 99%

Birefringence of the central cornea in children assessed with scanning laser polarimetry

Irsch

Shah

2012

J. Biomed. Opt

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Abstract. Corneal birefringence is a well-known confounding factor with all polarization-sensitive technology used for retinal scanning and other intraocular assessment. It has been studied extensively in adults, but little is known regarding age-related differences. Specifically, no information is available concerning corneal birefringence in children. For applications that are geared towards children, such as retinal birefringence scanning for strabismus screening purposes, it is important to know the expected range of both corneal retardance and azimuth in pediatric populations. This study investigated central corneal birefringence in children (ages three and above), by means of scanning laser polarimetry (GDx-VCC™, Carl Zeiss Meditec, Inc.). Children's measures of corneal retardance and azimuth were compared with those obtained in adults. As with previous studies in adults, corneal birefringence was found to vary widely in children, with corneal retardance ranging from 10 to 77 nm, and azimuth (slow axis) ranging from −11°to 71°(measured nasally downward). No significant differences in central corneal birefringence were found between children and adults, nor were significant age-related differences found in general. In conclusion, establishing knowledge of the polarization properties of the central cornea in children allows better understanding, exploitation, or bypassing of these effects in new polarization-sensitive pediatric ophthalmic applications.

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“…The resultant lamellar orientation in the stromal center is random, but towards the limbus, this orientation becomes more ordered, and a preferential axis appears. This creates stronger birefringent properties of this structure 1 . Each lamella contains collagen fibrils embedded in ground substance, each with different refractive indices.…”

Section: Introductionmentioning

confidence: 99%

The effect of pupil size on the measurement of corneal birefringence properties: preliminary study

Sobczak,

Asejczyk,

Wilczyński

2023

Sci Rep

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We used a partial Mueller matrix polarimeter to measure the corneal anisotropic properties at three pupil sizes (dilated, natural, and constricted). The geometrical parameters of first order isochromes were described by quadrilaterals. These parameters are statistically significantly different between the three pupil sizes. The pupillary size changes do not influence the azimuth angle distribution α. The retardation R and birefringence distributions show asymmetry in the nasal–temporal cross-section. There are differences between pupil sizes for both nasal and temporal parts of the cornea for these distributions. Iridial light scattering and diffraction might be the reason for these differences.

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The theory and implications of the biaxial model of corneal birefringence

Cited by 14 publications

References 51 publications

Comparative analysis of the corneal birefringence pattern in healthy children and adults

Comparative analysis of the corneal birefringence pattern in healthy children and adults

Birefringence of the central cornea in children assessed with scanning laser polarimetry

The effect of pupil size on the measurement of corneal birefringence properties: preliminary study

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