Numerical modeling of the cornea’s lamellar structure and birefringence properties

Abstract

A model of the cornea's lamellar structure is proposed that is capable of explaining experimental results obtained for the transmission of normal-incidence polarized light through rabbit and bovine cornea. The model consists of a large number of planar lamellae, each approximated as a uniaxial birefringent layer, stacked one upon another with various angular orientations. Polarized light transmission through the composite system is modeled theoretically by use of the Jones matrix formalism. The light transmission is calculated numerically for a large number of model lamellae arrangements, each generated from a statistical description, and histograms are constructed of various properties of the light transmission, including the minimum and maximum cross-polarized output intensities. It is demonstrated that various structural and optical parameters of the lamellae arrangements of actual corneas may be estimated by comparison of the calculations with detailed experimental data. Certain characteristics of the histograms are identified that permit a clear distinction between random and partially ordered systems. Comparisons with previously published experimental data provide strong evidence that the lamellae orientations are not entirely random, but rather a significant fraction are oriented in a fixed, preferred direction.

Keratoconus Diagnosis Using Anterior Segment Polarization-Sensitive Optical Coherence Tomography

“…It is well known that corneal birefringence results from highly organized collagen fibrils aggregated in bundles, which give rise to approximately 200 lamellae in the stroma. [15][16][17][18][19][20][21][22][23][24] Thus, each lamella is composed of parallel collagen fibrils embedded in an optically homogenous substance. In keratoconic corneas, the arrangement of regular fibril lamellae is altered, 22,25,26 with consequent modifications in their birefringence.…”

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

“…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.…”

Modeling the corneal birefringence of the eye toward the development of a polarimetric glucose sensor

“…6 The cornea changes the state of polarization of the transmitted beam due to the structure of corneal stroma, which mainly consists of collagen lamellae. [7][8][9] Each lamella exhibits intrinsic birefringence and can be considered a linear retarder with the fast axis perpendicular to the fibril orientation. The total corneal birefringence manifests itself as form birefringence, and can be considered as the sum of individual lamella birefringence.…”