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Figure 1: The optical intensity |
The photonic properties of the vertebrate retina are not very well understood. Its complex optical, anatomical and physiological properties ultimately determine the final visual response. Recent advances in computational modelling and biomedical optics have allowed scientists studying these properties to approach them in new ways.
Leigh Fischer and Dr Andrei Zvyagin of the Centre for Biophotonics and Laser Science at UQ, in collaboration with Dr Misha Vorobyev of UQ's Centre for Vision, Touch and Hearing, are studying various aspects of the photoreceptor optics in animals and humans. In particular they are focusing on characterising the photonic properties of the retina. The retina has, over thousands of years, been optimised for particular conditions, and it is thought that the highly efficient soft photonic structures present in these visual systems may be of great interest for potential commercial applications, such as advances in biomedical imaging.
One problem they are looking at is the effect of the distribution of photoreceptors in the human retina - clicking on Figure 1 will open an animation showing the optical intensity distribution in the retinal mosaic as a function of the photoreceptor packing density.
Leigh's work is primarily focused on the modelling of optical signal transduction in the retina. In order to make this simpler, the retina may be thought of as a waveguide, in which differential equations describing the magnetic field must be solved. One method being used is known as Finite-Difference Time-Domain (FDTD) computational modelling. FDTD is a computational modelling technique used for solving Maxwell's equations of electromagnetics, first developed by Kane S. Yee in 1966. However the poor computational capabilities of computers at the time meant that the technique wasn't practical, and it took nearly 10 years for there to be sufficient advances to make it feasible on a wide range of problems.
The FDTD software package used by the group is Lumerical FDTD Solutions. This software is capable of generating two and three dimensional simulations of a variety of boundary conditions, radiation sources and materials, and can export simulations as mpg movies. Data generated may also be exported to MATLAB or other ASCII formats for further analysis. The software is highly parallelizable, and so the use of the QCIF-funded supercomputers at UQ's HPC facility allows the group to run larger simulations much faster.
Contacts
Leigh Fischer, Dr Andrei Zvyagin,
Centre for Biophotonics and Laser Science,
University of Queensland
Misha Vorobyev
Vision, Touch and Hearing Research Centre,
University of Queensland
Written by T. Curtis, September 2006.