Figure 6. Major spectral components in porcine outer segments

Raman spectra, acquired using 633 nm excitation, of the major spectral components in each of the three outer segments, POS, PIS, and ONL, of porcine retina, as identified using principal component analysis (PCA). The designations "high" and "low" on the diagram are terms originating from principal component analysis usage and refer to extremes in the biochemical composition within each of the layers. For simplicity only two major biochemical components contributing to a given layer are considered. "High" score spectra represent regions where one biomolecular component has its highest contribution while the other has its lowest. A "low" score spectrum refers to the opposite combination of the two biomolecules in that layer. These "high" and "low" spectra, corresponding to the two major components in each layer (a total of six for the three layers) were used to generate the Raman map shown in Figure 2.