The Collaborative International Dictionary of English v.0.48:

amaurosis \am`au*ro"sis\ ([a^]m`[add]*r[=o]"s[i^]s), n. [Gr.
   'amay`rosis, fr. 'amayro`s dark, dim.] (Med.)
   A loss or decay of sight as the result of a neurological
   disease, without any perceptible changes in the eye; --
   called also gutta serena, the "drop serene" of Milton.
   [1913 Webster + AS]

   Amaurosis fugax (Med.), Temporary amaurosis
      [AS]

WordNet (r) 3.0 (2006):

amaurosis
    n 1: partial or total loss of sight without pathology of the
         eye; caused by disease of optic nerve or retina or brain