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Drusen, from the German word for node or geode (singular, "Druse"), are tiny yellow or white accumulations of extracellular material that build up between Bruch's membrane and the retinal pigment epithelium of the eye. The presence of a few small ("hard") drusen is normal with advancing age, and most people over 40 have some hard drusen. [1]
Optic disc drusen (ODD) are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc. [ 1 ] [ 2 ] They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells .
Following his remarks on the propagation medium and the speed of light, Huygens gives a geometric illustration of the wavefront, the foundation of what became known as Huygens’ Principle. His principle of propagation is a demonstration of how a wave of light (or rather a pulse) emanating from a point also results in smaller wavelets: [12]
Choroidal nevus with drusen can be considered as a sign of chronicity since drusen take years to develop and appear. [14] Drusen are composed of lipids and can actually be an indicator that a tumour is a benign nevus as opposed to a cancerous melanoma. [15] In nevi imaged by OCT, about 41% are found to have drusen. [16]
Diffraction spikes are lines radiating from bright light sources, causing what is known as the starburst effect [1] or sunstars [2] in photographs and in vision. They are artifacts caused by light diffracting around the support vanes of the secondary mirror in reflecting telescopes , or edges of non-circular camera apertures , and around ...
Photograph of a triangular prism, dispersing light Lamps as seen through a prism. In optics, a dispersive prism is an optical prism that is used to disperse light, that is, to separate light into its spectral components (the colors of the rainbow). Different wavelengths (colors) of light will be deflected by the prism at different angles. [1]
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The two waves can arrive at the receiver at slightly different times and the aberrant wave may arrive out of phase with the primary wave due to the different path lengths. Depending on the magnitude of the phase difference between the two waves, the waves can interfere constructively or destructively. The size of the calculated Fresnel zone at ...