Hemeralopia: Difference between revisions
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Otherwise, treatment relies on identifying and treating any underlying disorder. |
Otherwise, treatment relies on identifying and treating any underlying disorder. |
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Some people with hemeralopia have benefitted from having their eyes tested in a brightly lit room using a Snellen chart. Lens prescriptions obtained using this method can provide significant improvement in vision. |
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==See also== |
==See also== |
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Revision as of 10:45, 1 October 2017
| Hemeralopia | |
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| Specialty | Ophthalmology  |
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. However, it has been used in an opposite sense by many non-English-speaking doctors.[1] It can be described as insufficient adaptation to bright light. It is also called heliophobia and day blindness.[2]
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 are affected by hemeralopia and in turn degrade the daytime optical response. Hence many patients feel they see better at dusk than in daytime.
Causes
Hemeralopia is known to occur in several ocular conditions. Cone dystrophy and achromatopsia, affecting the cones in the retina, and the anti-epileptic drug Trimethadione are typical causes. Adie's pupil which fails to constrict in response to light; Aniridia, which is absence of the iris; Albinism where the iris is defectively pigmented may also cause this. Central Cataracts, 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 incite the production of deleterious antibodies against retinal components, 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.
Yet another cause of hemeralopia is uni- or bilateral postchiasmatic brain injury.[3] This may also cause concomitant night blindness.[3]
Management
People with hemeralopia may benefit from sunglasses. Wherever possible, environmental illumination should be adjusted to comfortable level.[3] Light-filtering lenses appear to help in people reporting photophobia.[3]
Otherwise, treatment relies on identifying and treating any underlying disorder.
See also
References
- ^ Ohba N, Ohba A (December 2006). "Nyctalopia and hemeralopia: the current usage trend in the literature". Br J Ophthalmol. 90 (12): 1548–9. doi:10.1136/bjo.2006.097519. PMC 1857511. PMID 17114591.
- ^ Gördüren, S. (1950). "Day-Blindness". British Journal of Ophthalmology. 34 (9): 563–567. doi:10.1136/bjo.34.9.563. PMC 1323631. PMID 14777856.
- ^ a b c d Page 96 in: Zihl, Josef (2000). Rehabilitation of visual disorders after brain injury. East Sussex: Psychology Press. ISBN 0-86377-898-4.
4. Thirkill CE. Cancer-Induced Retinal Degenerations.
2005, Ocul Immunol Inflamm 13:119-131