Editing Vitamin A (section)

====Xerophthalmia and childhood blindness====
{{Main|Xerophthalmia}}
[[File:Typical location of Bitot's spots.jpg|thumb|Typical location of Bitot's spots]]
Xerophthalmia, caused by a severe vitamin A deficiency, is described by pathologic dryness of the conjunctival epithelium and cornea. The conjunctiva becomes dry, thick, and wrinkled. Indicative is the appearance of Bitot's spots, which are clumps of keratin debris that build up inside the conjunctiva. If untreated, xerophthalmia can lead to dry eye syndrome, [[corneal ulceration]] and ultimately to blindness as a result of cornea and retina damage. Although xerophthalmia is an eye-related issue, prevention (and reversal) are functions of retinoic acid having been synthesized from retinal rather than the 11-''cis''-retinal to rhodopsin cycle.<ref name="Akhtar2013"/>

Throughout southeast Asia, estimates are that more than half of children under the age of six years have subclinical vitamin A deficiency and night blindness, with progression to xerophthalmia being the leading cause of preventable childhood blindness.<ref name="Akhtar2013">{{cite journal | vauthors = Akhtar S, Ahmed A, Randhawa MA, Atukorala S, Arlappa N, Ismail T, Ali Z | title = Prevalence of vitamin A deficiency in South Asia: causes, outcomes, and possible remedies | journal = Journal of Health, Population, and Nutrition | volume = 31 | issue = 4 | pages = 413–423 | date = December 2013 | pmid = 24592582 | pmc = 3905635 | doi = 10.3329/jhpn.v31i4.19975 }}</ref> Estimates are that each year there are 350,000 cases of childhood blindness due to vitamin A deficiency.<ref name="Whitcher2001">{{cite journal | vauthors = Whitcher JP, Srinivasan M, Upadhyay MP | title = Corneal blindness: a global perspective | journal = Bulletin of the World Health Organization | volume = 79 | issue = 3 | pages = 214–221 | date = 2001 | pmid = 11285665 | pmc = 2566379 | doi = }}</ref> The causes are vitamin A deficiency during pregnancy, followed by low transfer of vitamin A during lactation and infant/child diets low in vitamin A or β-carotene.<ref name="Akhtar2013"/><ref name="Whitcher2001"/> The [[prevalence]] of pre-school age children who are blind due to vitamin A deficiency is lower than expected from [[Incidence (epidemiology)|incidence of new cases]] only because childhood vitamin A deficiency significantly increases all-cause mortality.<ref name="Whitcher2001"/>

According to a 2017 Cochrane review, vitamin A deficiency, using serum retinol less than 0.70&nbsp;μmol/L as a criterion, is a major public health problem affecting an estimated 190 million children under five years of age in low- and middle-income countries, primarily in Sub-Saharan Africa and Southeast Asia. In lieu of or in combination with food fortification programs, many countries have implemented public health programs in which children are periodically given very large oral doses of synthetic vitamin A, usually retinyl palmitate, as a means of preventing and treating vitamin A deficiency. Doses were 50,000 to 100,000 IU ([[International unit]]s) for children aged 6 to 11 months and 100,000 to 200,000 IU for children aged 12 months to five years, the latter typically every four to six months. In addition to a 24% reduction in all-cause mortality, eye-related results were reported. Prevalence of Bitot's spots at follow-up were reduced by 58%, night blindness by 68%, xerophthalmia by 69%.<ref name="Imdad2017"/>