Vitamin A

Xerophthalmia Vernacular TermsXerophthalmia Vernacular Terms

Matang Manok Mata Ajam Khwak Moan Gred Gradei Mager Aagh Korapothu

Chicken Eyes Chicken Eyes Dusk Blindness Scaly as Fish Fish Scales Scaly

Tagalog Indonesian Khmer Thai Bengali Singhalese

Impact of VADD on Public HealthImpact of VADD on Public Health

• 250 million preschool-age children have subclinical vitamin A deficient

•7.2 million pregnant women

• 3 million have clinical xerophthalmia

• 300, 000 are blind from xerophthalmia

Impact of Vitamin A Intervention on Impact of Vitamin A Intervention on Child SurvivalChild Survival

“Improvement of vitamin A status in young child populations… leads to a reduction in all-cause mortality rates of about 23%.”

United Nations, 1993

“Improved vitamin A nutriture would be expected to prevent approximately 1.3-2.5 million deaths annually among children aged under 5 years.”

Bulletin of WHO, 1992

BUT Mechanisms involved are poorly understood

FunctionsFunctions

• Vision (night, day, colour)

• Epithelial cell integrity against infections

• Immune response

• Haemopoiesis

• Skeletal growth

• Fertility (male and female)

• Embryogenesis

Tests of Vitamin A StatusTests of Vitamin A Status

Subclinical

• Relative dose-response test

• Serum retinol

• Retinal rod function

• Conjunctival impression cytology (CIC)

Clinical

• Night blindness

• Conjunctival and corneal eye signs

Decreased Status

• Liver disease deacreases plasma retinal levels, probably as a result of a combination of decreased synthesis and secretion of RBP.

• Stress decreases plasma retinol levels.

• Protein-energy malnutrition decreases RBP production because of a limited supply of protein substrate. Consequently hepatic release of vitamin A is impaired resulting in decreased serum retinol levels.

• Zinc deficiency decreases plasma retinol levels via its role in the synthesis of RBP.

Factors that may Affect Plasma Factors that may Affect Plasma Vitamin A or Retinol LevelsVitamin A or Retinol Levels

• Infections and parasitic infections lower plasma retinol levels.

• Cystic fibrosis is associated with a defect in the transport of vitamin A from the hepatic stores to the periphery resulting in decreased levels of circulating retinol and RBP.

• Low fat diets impair absorption of vitamin A, lowering plasma retinol concentrations.

• Estrogens, either endogenous or those used in contraceptive agents, increase plasma retinol and RBP apparently as a result of incresed mobilization of Vitamin A from the liver.

• Age, sex and race influence serum retinol levels, as indicated by the NHANES II survey results.

For the test, a baseline blood sample is taken immediately before the administration of a small oral dose (450µg) of

vitamin A (as retinyl acetate or retinol palmitate); followed by a second blood sample, five hours later. The RDR (%) is

calculated as:

RDR(%) =Plasma retinol at 5 hr – Plasma retinol at 0hr

Plasma retinol at 5 hrX 100

Vitamin-A-replete subjects have RDR values ranging from 0% to 14%. Relative dose response values greater than 14%

to 20% are indicative of marginal vitamin A status in humans, the cutoff value depending on the coefficient of

variation for the analytical method used to measure serum

<20

21 - 29

30 - 40

>40

100

86

26

3

12

21

19

39

Serum Retinol (µg/dL) % Number Tested

Total tested 91

Percentage of Children with Positive Percentage of Children with Positive RDR Test Classified by Serum Retinol RDR Test Classified by Serum Retinol

LevelsLevels

Treatment Schedule (orally)Treatment Schedule (orally)

Immediately on diagnosis:

50, 000 IU<6 months

100, 000 IU6 months-12 months

200, 000 IU> 12 months

Next day Same age-specific dose

At least two weeks later Same age-specific dose

Xerophthalmia ClassificationXerophthalmia Classification

XN

X1A

X1B

X2

X3A

X3B

Night Blindness

Conjunctival Xerosis

Bitot’s Spot with Conjunctival Xerosis

Corneal Xerosis

Corneal Xerosis with ulceration

Keratomalcia

XF Xerophthalmic Fundus

XS Corneal scars from Xerophthalmia

WHO criteria of a public health WHO criteria of a public health problem of xerophthalmiaproblem of xerophthalmia

• Night Blindness (XN) In > 1%

• Bitots spot (X1B) In > 0.5%

(X2, X3A, X3B) In >0.01%

• Corneal Xerosis/Ulceration/Keratomalacia

• Corneal scar (XS) In > 0.05%

• Plasma retinol of <0.35µmol/l (10 µg/dl)

In > 5%

Percent with Serum Vitamin A:

Children with night-blindness or Bitot’s spots

Normal Children

Children with corneal xerophthalmia

<10 µg/dL 10-19 µg/dL >20 µg/dLn

252

325

98

8

75

30

37

24

15

55

1

55

Serum vitamin A levels in a sample of Indonesian children with and without ocular lesions. Conversion factor SI units(µmol/L)=

x 0.035