- Also known as hemeralopsia and day blindness. The term hemeralopia comes from the Greek words hèmera (day), alaos (blind), and ops (eye). It was introduced into the biomedical literature during the 18th century to denote an ocular condition characterized by a deterioration of vision in bright light, combined with a retention of vision in dim light and in the dark. Hemeralopia is usually classified as an "entoptic phenomenon. Pathophysiologically, it is associated primarily with a loss or impairment of cone photorecep-tor function. Etiologically, it is associated with a variety of conditions ranging from hyperaes-thesia of the retina to cone dystrophy, cone dysfunction syndrome, Stargardt's disease, and retinal ischaemia. A physiological and transient form of hemeralopia may occur following the sudden transition from darkness to bright light. Conceptually, hemeralopia is the logical counterpart of " nyctalopia or night blindness. Phenomenologi-cally, it shows certain similarities with " scieropia and " scierneuropsia, two conditions which are also characterized by a deterioration of vision in bright light. In the continental European literature (notably French, German, and Italian) the term hemeralopia is sometimes used to denote night blindness instead of day blindness. To prevent conceptual confusion due to this paradoxical usage of the term, some authors prefer the term day blindness.ReferencesOhba, N., Ohba, A. (2006). Nyctalopia and hemeralopia: The current usage trend in the literature. British Journal of Ophthalmology, 90,1548-1549.
Dictionary of Hallucinations. J.D. Blom. 2010.