D. De Brouwere

Optical simulation of large and small angle scatterers

Purpose However corneal scattering is clinically often quantified as haze (backscattered light), the visual function is affected by the forward light scattering in the anterior ocular media. The angular light distribution of the scattered light is inherent to the interaction between the light and the scattering media. The purpose of this study is to describe an optical model of the scattering tissues in the cornea and compare its light propagation to experimental single pass scattering measurements. Methods Histologic data and confocal imaging of the cornea revealed that a significant portion of corneal scattering originates by keratocytes and scar tissue created during a wound healing process, e.g. after refractive surgery. Keratocytes were modeled as small spheres, angular scattering distribution is derived on the Mie theory. The parameters were optimized to meet the light distribution measure by a single pass experiment through excised rabbit corneas. Results Single pass scatter measurements of excised rabbit corneas revealed a narrowly forward peaked scattering distribution (FWHM 30 arcmin), corresponding to a distribution of scattering spheres with 36μm+/-15 radius and a relative refractive index of 1.0024. Scattering ratio (SR), equal to the scattering cross section, varied from 0.2 (clear) to 0.7 (scarred). The SR was correlated with the scar tissue thickness (0.79) and haze grade (0.51), Pearsons coefficient. Conclusion Despite the non-spherical geometry of keratocytes, we presented a simple model to describe the corneal scattering distribution, controlled by physically relevant parameters as observed in histologic and confocal microscopy. Optical simulations based on light propagation through random phase maps may result in more realistic scattering models.