legal blindness

[lēgəl]
n.
  1. Visual acuity of less than 6/60 or 20/200 using Snellen test types, or visual field restriction to 20 degrees or less.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.