The theory and implications of the biaxial model of corneal birefringence.

Ophthalmic Physiol Opt

Department of Ophthalmology, Warwick Hospital, South Warwickshire NHS Trust, Warwick, UK.

Published: November 2010

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Article Abstract

Purpose: A theoretical model of biaxial optical anisotropy is derived and its structural, biomechanical and developmental implications are discussed with reference to known corneal anatomy. METHODS A concise review of the theory of optical crystallography is followed by the derivation of a theoretical model of the optical anisotropic properties of a dome of biaxial birefringent crystalline material. The model is then applied to parameters relevant to the biaxial model of human corneal birefringence.

Results: Theoretical distributions of refractive indices and vibration directions for transmitted monochromatic light are derived for the central and paracentral zones of a model human cornea. Contours of equal refractive index (equirefringence curves) are found to have orthogonal confocal spheroconic geometry.

Conclusions: A novel model of corneal structure is proposed in which discrete uniaxial positive birefringent fibre-like elements conform to the derived spheroconic geometry. Biomechanical implications and the relationship of the birefringent elements to known corneal anatomy are discussed. The crystallographic conventions are proposed as a standard for further investigations of corneal birefringence.

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http://dx.doi.org/10.1111/j.1475-1313.2010.00782.xDOI Listing

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