3. PHYSIOLOGY AND FUNCTIONS
OF VITAMIN A
Vitamin A (retinol) is part of the family of retinoids,
usually present in food and the body as esters combined
with long chain fatty acids.
Sources- liver(richest), milk, butter, cheeses, egg york
and fish oils.
Beta- carotene is the main carotenoid found in green
vegetables, carrots and other yellow and red fruits.
Other carotenoids, lycopene and lutein are of little
importance as dietary precursors of vit A.
4. Beta carotene is broken down in the intestinal mucosa
by carotene dioxygenase to yield retinaldehyde which
can be reduced to retinol.
Retinol is stored in the liver and is transported in
plasma bound to an alpha – globulin called retinol-
binding protein(RBP).
5. Roles of Vit A:
Retinaldehyde in its opsin form is found in the
rods(rhodopsin) and cones (iodopsin) of the retina.
Light causes retinaldehyde to change to its trans isomer
and this leads to changes in membrane potentials that
are transmitted to the brain.
Retinol and retinoic acid are involved in the control of
cell proliferation and differentiation
Retinyl phosphate is a cofactor in the synthesis of most
glycoproteins containing mannose.
6. Deficiency: xerophthalmia
Vitamin A deficiency and xerophthalmia is a major cause
of blindness in young children. WHO estimates 6 to 7
million new cases of xerophthalmia annualy with 20% of
survivors being totally blind and 50-56% partially blind.
South East Asia, parts of Africa and Latin America are
the most severely affected.
7. Risk factors
Malnutrition (PEM- retinol binding proteins and other
proteins are reduced suggesting Vit A defficiency though
body stores are not necessarily reduced )
Infections eg measles
Diarrhoeal diseases
Respiratory infections
Hiv – low circulating concentrations of vit A in HIV
infected individuals are associated with increased risk
of Vertical transmission of HIV. Supplementation during
pregnancy and intrapartum period is unlikely to reduce
vertical transmission to the child.
8. Signs and symptoms
Impaired adaptation followed by night blindness is the
first effect.
Dryness and thickening of the conjectiva and cornea.
Xerophthalmia occurs as a result of keratinization.
Bitot’s spots- white plaques of keratinized epithelial
cells found on conjuctiva of young children.( can also be
due to exposure)
Corneal softening, ulceration and dissolution
(keratomalacia)
Secondary bacterial infection
14. DIAGNOSIS
Clinically- where deficiency is common
Should always be suspected with any degree of
malnutrition
Low Vit A levels in blood
Response to replacement therapy
15. TREATMENT
Retinol palmitate 30mg orally on two successive days
In case of diarrhoea and vomiting, Vit A 30mg is given IM
Treat associated malnutrition
Treat superadded bacterial infection with antibiotics
Refer severe cases for specialist ophthalmic treatment.
16. PREVENTION
Most western diets contains enough dairy products and
green vegetables
In some countries vitamin A (eg margarine) is added to
foodstuffs- vit A is not destroyed by cooking.
In some developing countries vit A supplements are
given as part of the immunisation schedule
Food fortification programme
Health education for the general population- encourage
to grow their own vegetables.
Pregnant women and young children should be
encouraged to eat green vegetables.
17. TRACHOMA
World’s major infectious cause of blindness
Cause- intracellular bacterium chlamydia trachomatis
Prevalence: current infections estimated at 150 million
worldwide,
6 million blinded by trachoma
It’s a disease of poverty- found mainly in the tropics and
middle east
Its entirely preventable
18. TRACHOMA
Infection spreads from person to person, particularly
from child to child and from child to mother to child
either directly or by flies.
The disease thrives especially in crowded living
conditions where there are shortages of water,
inadequate sanitation and where numerous eye-seeking
flies are present. In affected communities, infection is
often first encountered in infancy or childhood.
Women are blinded 2 to 3 times more often than men,
probably due to their close contact with infected
children and their resulting greater frequency of
infection episodes .
19. Isolated infection is self limiting
The age at which people in a community start going
blind from trachoma is related to the intensity of
transmission of infection in the community. In endemic
areas, active (inflammatory) trachoma is common
among preschool-aged children, with prevalence rates
as high as 60-90%. Infection becomes less frequent and
shorter in duration with increasing age
Early stages are symptomless
Infection is bilateral and begins at the conjectiva with
marked follicular inflammation.
20. Clinical features
With repeated infections over many years, the
cumulative effect of many inflammatory episodes may
cause the upper eyelid to turn inwards, so that the
eyelashes rub on the eyeball, resulting in intense pain
and scarring of the front of the eye. This is called
trachomatous trichiasis, and ultimately leads to
irreversible blindness.
21. WHO grading system for
trachoma
Trachomatous Inflammation – Follicular (TF) - which
mostly requires topical treatment.
Trachomatous Inflammation – Intense (TI) - during which
topical and systemic treatments are considered.
Trachomatous Scarring (TS) - when scars are visible as in
the tarsal conjunctiva and which may obscure tarsal
blood vessels.
Trachomatous Trichiasis (TT) - when an individual is
referred for eyelid surgery; and
Corneal Opacity - a stage during which a person is
irreversibly blind.
22.
23. Diagnosis and management
Typically clinical- people are examined for clinical signs
through use of magnifiers. Can be confirmed by cell
culture techniques or species-specific flourescent
monoclonal antibodies- rarely available
S = surgical care
A = antibiotics
F = facial cleanliness
E = environmental improvement
24. Treatment involves screening communities for the
presence of trachoma in children 1-9 years of age.
When over 10 % are found to have clinical disease, the
entire community is treated with antibiotics. In areas
with less disease, only targeted groups are treated.
Due to the contagiousness of trachoma, it is necessary
to treat all who might be in contact with the infected
individuals.
25. Treatment
WHO SAFE Approach :
S = surgical care
A = antibiotics
TEO daily for 6-8 WEEKS
Treatment of choice- Systemic Azithromycin 20mg/kg
single dose
Can be repeated in endemic areas
Surgery for eyelid reconstruction and for treatment of
corneal opacities.
26. Prevention
Community health education
Improvement of water supply and sanitation
Teaching simple cleanliness
Early case reporting
WHO SAFE strategy approach:
F = facial cleanliness
E = environmental improvement
WHO target is global eradication by 2020
27. Trachoma often infects entire families and
communities. Children, who are more likely to touch
their eyes and have unclean faces that attract eye-
seeking flies, are especially vulnerable to infection, as
are women, the traditional caretakers of the home.
Therefore, the promotion of good hygiene practices,
such as hand washing and the washing of children's
faces at least once a day with water, is a key step in
breaking the cycle of trachoma transmission.
28. Improvements in community and household sanitation can be by:
provision of household latrines to control fly populations and breeding
grounds.
Increased access to water to facilitate good hygiene practices vital to
achieving sustainable elimination of the disease.
Separation of animal quarters from human living space
Safe handling of food and drinking water
29. Complications of Trachoma
Blindness- partial or complete
Inability to work
Children drop out of school
Severe economic problems for the family
Increased number of related injuries
Accidental death.
30. What is the prognosis for
trachoma?
If diagnosed early, before scarring of the cornea, the
prognosis is excellent.
There is an International Trachoma Initiative (ITI)
dedicated to eliminating trachoma by following the
World Health Organization (WHO) SAFE strategy in
partnering with governmental and private organizations,
such as the Bill & Melinda Gates Foundation. If
successful, trachoma may become a disease of the past
in two generations; 15 countries are targeted for
elimination of trachoma by 2020.
