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Nyctalopia (/ ˌ n ɪ k t ə ˈ l oʊ p i ə /; from Ancient Greek νύκτ-(núkt-) 'night' ἀλαός (alaós) 'blind, invisible' and ὄψ (óps) 'eye'), [1] also called night-blindness, is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases.
Retinitis pigmentosa is the leading cause of inherited blindness, [51] with approximately 1/4,000 individuals experiencing the non-syndromic form of their disease within their lifetime. [52] It is estimated that 1.5 million people worldwide are currently affected.
The condition is not congenital and develops over the course of a few months as the lacrimal glands fail to produce tears. Other conditions involved in the progression already stated include the appearance of Bitot's spots, which are clumps of keratin debris that build up inside the conjunctiva and night blindness, which precedes corneal ulceration and total blindness.
This condition is one of the leading causes that leads to blindness in patients in the age range of 20–60 years old. Retinitis may be caused by several infectious agents, including toxoplasmosis, [1] cytomegalovirus and candida. [2] Cytomegalovirus retinitis is an important cause of blindness in AIDS patients. [2]
Retinitis pigmentosa, mid stage. Kearns and Sayre described patients with "pigmentary degeneration" on funduscopy, night vision abnormalities, and some histologic similarities, but also clinical differences, to retinitis pigmentosa [2] Subsequently, the retinal phenotype of KSS was described as retinitis pigmentosa, atypical retinitis pigmentosa, tapetoretinal degeneration, salt-and-pepper ...
Night blindness and its worsened condition, xerophthalmia, are markers of Vitamin A deficiency; collections of keratin in the conjunctiva, known as Bitot's spots, and ulceration and necrosis of cornea keratomalacia can be seen. Conjunctival epithelial defects occur around lateral aspect of the limbus in the subclinical stage of VAD.
Congenital stationary night blindness (CSNB) is a rare non-progressive retinal disorder. People with CSNB often have difficulty adapting to low light situations due to impaired photoreceptor transmission. These patients may also have reduced visual acuity, myopia, nystagmus, fundus abnormalities, and strabismus.
Oguchi disease present with nonprogressive night blindness since young childhood or birth with normal day vision, but they frequently claim improvement of light sensitivities when they remain for some time in a darkened environment.