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    Optic nerve drusen. (A) early prearterial phase shows fluorescence of optic nerve drusen. Very small amount of dye can be seen in one retinal artery. (B) In arterial phase, drusen still fluorescence, has contrast between drusen and remainder of retinal tissue is less because choriocapillaris and retinal arteries are now filled. Contrast between drusen and optic disc is also decreased by filling of capillary net on optic disc. (C) In arteriovenous phase, remainder of optic disc fluoresce as a result of dye in capillary net on optic disc and dye permeating from adjacent choriocapillaris. Drusen can no longer by differentiated from other tissues. (D) Late phase. All fluorescein has emptied from choroidal and retinal circulation. Drusen retain some fluorescein dye and are now brighter than in early prearterial phase (part A) prior to appearance of dye.