This section is from "The American Cyclopaedia", by George Ripley And Charles A. Dana. Also available from Amazon: The New American Cyclopędia. 16 volumes complete..
Amaurosis (Gr., from dark), partial or complete loss of sight, dependent on a change in the nerve structure of the eye. The term was formerly used to denote any loss of sight the cause of which could not be appreciated by the naked eye; but the invention of the ophthalmoscope has been the means of restricting it to those cases in which the optic nerve or its expansion, the retina, has undergone atrophy, or its component parts are so pressed upon that they are no longer capable of performing their functions. The tissue which holds together the fibres of the optic nerve being in close connection with that covering the bone in its vicinity, and with the membranes of the brain, an inflammation of these latter may by extension induce the disease. A haemorrhage (apoplexy), or a tumor near or in the nerve, may by pressure cause this condition; or even a plugging of the artery which should supply the nerve with blood; or, finally, certain diseases of the brain or spinal cord, or of the nerve itself. The disease is usually progressive. If the cause be mechanical from pressure, of recent origin, and removable by treatment before change in the nerve structure has proceeded too far, the vision may be restored or its further loss prevented.
Such cases are exceptional.
 
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