Xerophthalmia is a condition of early vitamin A deficiency in which cornea keratinises, become opaque and forms dry, scaly layers of cells. Affected cornea is susceptible to infection. The conjunctiva may keratinise and develop plaques known as Bitot’s spots. In1863, Pierre Bitot, a French physician, first described these spots.
The eye lesions are primarily disease of the young and are a major cause of blindness in developing countries. Although rates of xerophthalmia have fallen, the number of affected children is still high.
Vitamin A deficiency
The risk of vitamin A deficiency is small in children who are getting vitamin A (retinol) or its precursors. Deficiency states are common in many developing countries and are often associated with global malnutrition. Barring impoverished populations, deficiency of vitamin A is rare in developed countries. Vitamin A deficiency may also be seen as a complication with various chronic disorders or diseases in children. Medical history related to dietary habits may be important in identifying nutritional disorders.
In eye, vitamin A is metabolised to form rhodopsin (retinal visual pigment). Action of light on rhodopsin is the initial step in the visual process.
Pre-formed vitamin A is available in foods of animal origin only. Vitamin A may be obtained from carotenes, which are present in green and coloured vegetables and yellow fruits. Carotenes provide vitamin A to the vegetarians.
Malnutrition, especially protein deficiency, may also cause vitamin A deficiency. Clinical or sub-clinical zinc deficiency may also increase the risk of vitamin A deficiency.
Except for vitamin A, toxicity from excess intake of vitamins is less common. Excessive intake of carotene (precursor of vitamin A) may lead to pigmentation of skin (hypercarotenosis). This gets reduced and fades away when intake of carotene is reduced.
References
http://apps.who.int/iris/bitstream/10665/133705/1/WHO_NMH_NHD_EPG_14.4_eng.pdf
http://apps.who.int/iris/bitstream/10665/41887/1/9241544929.pdf
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3936686
https://www.ncbi.nlm.nih.gov/pubmed/6829680
http://whqlibdoc.who.int/trs/WHO_TRS_672.pdf
http://medicalpoint.org/xerophthalmia
World Health Organisation. Control of Vitamin A Deficiency and Xerophthalmia, Technical Report Series 672, Geneva, 1982.
Symptoms of vitamin A deficiency are associated with the requirement of vitamin A for the maintenance of epithelial functions.
Symptoms include
Besides eye lesion, child with vitamin A deficiency may have systemic features such as growth retardation, susceptibility to infections, anaemia, diarrhoea, mental retardation, apathy, increased intracranial pressure, and wide separation of the cranial bone at the sutures.
There are low levels of vitamin A in plasma, liver, and extra-hepatic tissues of neonates, as compared to adults. Normal plasma levels increase gradually as child grows.
Vitamin A deficiency and xerophthalmia still occur throughout much of the developing countries and are linked to under-nourishment. Vitamin A deficiency may also be seen as complication in children with various chronic disorders or diseases. Malnutrition, particularly protein deficiency, may cause vitamin A deficiency because of the impaired vitamin A carrying protein.
Eye lesions are the most specific and characteristic features of vitamin A deficiency, but these may manifest rather late in the progression of deficiency. Lesions caused by vitamin A deficiency develop insidiously and rarely manifest before two years of age.
Besides the important features such as delayed dark adaptation, night blindness, and photophobia, the corneal/ conjunctival epithelium is severely affected.
Pathology
Characteristic changes as a result of vitamin A deficiency in epithelial cells include proliferation of basal cells, hyperkeratosis, and formation of cornified squamous epithelium. The combination of defective epithelial barrier to infection, low immune response, and lowered response to inflammatory stress leads to associated health problems.
Delayed adaptation to the dark is due to reduced re-synthesis of visual pigment rhodopsin in retina.
The retinal pigment epithelium degenerates, pigment containing retinal rods and cones loose support and thus break down, resulting in blindness.
Diagnosis depends upon history, clinical examination and laboratory investigations.
A dietary history is important in diagnosis or ruling out low intake, being the aetiological factor.
Early vitamin A deficiency shows delayed dark adaptation.
Keratinised conjunctiva shows Bitot’s spots at a relatively early stage.
Cornea shows dry and scaly layers of cells known as xerophthalmia. Cornea may degenerate and produce keratomalacia, corneal ulceration, necrosis, and permanent corneal scars.
World Health Organisation (WHO) criteria for diagnosis of xerophthalmia in community:
Clinical criteria by ocular signs
XN Night blindness
X1A Conjunctival xerosis
X1B Bitot’s spot
X2 Corneal xerosis
X3A Corneal ulceration/keratomalacia <1/2 corneal surface
X3B Corneal ulceration/keratomalacia ≥1/2 corneal surface
XS Corneal scar
XF Xerophthalmic fundus
Biochemical criteria
Serum vitamin A (retinol) less than 10μg/100 ml (0.35μmol/liter)
Measurement of plasma retinol level is not an accurate indicator of vitamin A status. However, measurement of plasma levels of retinol may be important in cases with severe vitamin A deficiency and with depleted stores in liver.
Clinical or even subclinical vitamin A deficiency is associated with immunodeficiency leading to increased chances of infection such as measles and increased risk of mortality, especially in developing countries.
Management should be carried out under medical supervision.
Xerophthalmia and vitamin A deficiency requires urgent treatment.
Supportive therapy:
Topical therapy:
Systemic medical therapy:
Vitamin A supplementation for deficiency state depends upon safety and efficacy of its use.
A daily supplement of 1500μg of vitamin A is normally sufficient for latent cases of vitamin A deficiency, but recommended dietary allowance (RDA) levels may be the goal after this intake (which covers needs of >97% of population).
Xerophthalmia cases may require 1500μg/kg of body weight orally for five days followed by 7500μg of vitamin A in oil given intramuscularly, till recovery.
World Health Organisation (WHO) is giving high priority to prevention of vitamin A deficiency in communities where xerophthalmia occurs. They have recommended giving single prophylactic oral dose of retinyl palmitate (an ester of retinol or vitamin A) to pre-school children.
WHO treatment schedule for xerophthalmia
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Timing Dosage by mouth
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Immediately on diagnosis (by age):
< 6 months 27.5 mg retinyl palmitate (50000 IU)
6- 12 months 55 mg retinyl palmitate (100000 IU)
>12 months 110 mg retinyl palmitate (200000 IU)
Next day Same age specific dosage
If clinical deterioration occurs or, when Same age specific dosage
possible, 1- 4 weeks later
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Intramuscular injection of water- miscible retinyl palmitate at half these dosages may be substituted in rare instances, when swallowing is severely impaired, vomiting is persistent or severe mal-absorption prevents an adequate response.
Surgical therapy:
Surgery plays limited role in the management of xerophthalmia. It is of no use when there is complete corneal necrosis.
This may produce complications and leave sequelae such as corneal opacity and blindness.
Prevention may involve
