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ICD-10 H53.1
ICD-9 368.6
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Hemeralopia (from Greek ημέρα, hemera "day"; and αλαός, alaos "blindness") is the inability to see clearly in bright light and is the exact opposite of Nyctalopia (night blindness). Hemera was the Greek goddess of day and Nyx was the goddess of night.

In hemeralopia, daytime vision gets worse , characterised by photoaversion(dislike/avoidance of light) rather than photophobia(eye discomfort/pain in light) which is typical of inflammations of eye. Nighttime vision largely remains unchanged due to the use of rods as opposed to cones (during the day), which get affected by hemeralopia and in turn degrade the daytime optical response.Hence many patients feel they see better at dusk than in daytime.

Hemeralopia is known to occur in several ocular conditions.Cone dystrophy affecting the cones in the retina, and anti-epileptic drug Trimethadione are typical causes.Adie's pupil which fail to constrict in response to light;Aniridia ,which is absence of iris;Albinism where iris is defectively pigmented may also cause this. Cataract,due to the lens clouding,disperses the light before it can reach the retina, is a common cause of hemeralopia and photoaversion in elderly.C.A.R(Cancer Associated Retinopathy)seen when certain cancers release deleterious antibodies against retinal structures, may cause hemeralopia.

Another known cause is a rare genetic condition called Cohen Syndrome (aka Pepper Syndrome). Cohen syndrome is mostly characterized by obesity, mental retardation, and craniofacial dysmorphism due to genetic mutation at locus 8q22-23. Rarely it may have ocular complications such as hemeralopia, pigmentary chorioretinitis, optic atrophy or retinal / iris coloboma, having a serious effect on the person's vision.

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suggested substance to have curable effect is Carotene