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WikiProject Medicine / Ophthalmology (Rated Start-class, Low-importance)
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According to my dictionary, hemeralopia is night blindness and nyctalopia day blindness, the opposite of what you say. Sanne

  • What dictionary are you using? -AED 07:43, 13 April 2006 (UTC)

I agree with the definition that says: hemeralopia is night blindness and nyctalopia day blindness. Ambra —The preceding unsigned comment was added by (talk) 11:27, August 21, 2007 (UTC)

Hemeralopia is being used both for day-blindness and night-blindness. Sources here ( and here ( —Preceding unsigned comment added by Mundaria (talkcontribs) 09:31, 3 December 2009 (UTC)

The Oxford English Dictionary explains (unedited copypaste):
‘Day-blindness’; a visual defect in which the eyes see indistinctly, or not at all, by daylight, but tolerably well by night or artificial light. (But used by many in the sense of ‘night-blindness’, nyctalopia n.)
‘Day-blindness’ is the etymological meaning of the word, and the sense in which ἡμεράλωψ, as the opposite of νυκτάλωψ, was used by Galen. But, as nyctalopia n. was, from an early date, taken by some in the opposite sense, these also reversed the etymological sense of hemeralopia, and used it as = ‘night-blindness’, ‘day-sight’, as if the word were hemeropia. ‘With the exception of Copland and Henry Power, all or most modern authors‥have used the term in the sense of night-blindness. The Royal College of Physicians of London have reverted to the true meaning of the word in their “Nomenclature of Diseases”’ ( New Sydenham Soc. Lexicon). But the Medical Dictionary of F. P. Foster, New York, 1891, continues the non-etymological sense of ‘day-vision, night-blindness’. The word was rightly used by Paré in 16th c.: Œuvres xv. 3 (Littré) Le contraire est quand on voit mieux de nuit que de jour, et se peut dire hemeralopia en grec, œil de chat en francois. --Thrissel (talk) 11:00, 12 April 2011 (UTC)