Measuring Scleral and Laminar Microstructure

Scleral and laminar fibre orientation can be characterised using an optical technique known as small angle light scattering. Such technique can derive fibre orientation by analysing the interaction of light with a biological tissue. Briefly, with SALS, a thin biological tissue is laid flat in a glass plate assembly, mounted in a custom holder, and positioned perpendicularly to the laser beam. It is then raster scanned with a 5 mW unpolarized HeNe laser using a motorised X-Y translation stage assembly. As light interacts with the tissue, it is scattered by the fibrous tissue proteins (mainly collagen) and projected onto a diffuser screen. The digitised light pattern can then be analysed with image processing algorithms in order to extract 2 essential microstructure parameters (i.e. the preferred fibre orientation and the degree of alignment) at each measurement location.

We have used SALS to map fiber orientation in thin sections of the human optic nerve head (see Figure above where colors indicate the degree of alignment - red and blue correspond to high and low degrees, respectively - and black vectors indicate the preferred fibre orientation). We found a highly aligned ring of fibres in the peripapillary sclera and radial fibres in the lamina cribrosa. We will use this technique to map fiber orientation in normal and glaucoma eyes to evaluate potential microstructural alterations in glaucoma.

This is a project in collaboration with Dr Ross Ethier from Georgia Tech and with Dr Julie Albon from Cardiff University.

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