night blindness

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A condition of the eyes in which vision is normal in daylight or other strong light but is abnormally weak or completely lost at night or in dim light. The condition may result from vitamin A deficiency, disease, or hereditary factors.

from The Century Dictionary.

• noun Inability to see in a dim light; nyctalopia. Also called daysight. See nyctalopia and hemeralopia.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The optic condition nyctalopia, the inability to see clearly in faint light, as at night

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun inability to see clearly in dim light; due to a deficiency of vitamin A or to a retinal disorder