«Prevention of Childhood Blindness Teaching Set © 1998, updated 2007, International Centre for Eye Health, London School of Hygiene & Tropical ...»
INTERNATIONAL CENTRE FOR EYE HEALTH
© 1998, updated 2007, International Centre for Eye Health, London School of Hygiene & Tropical Medicine, Keppel
Street, London, WC1E 7HT, UK. Web sites: www.iceh.org.uk and www.jceh.co.uk.
Supported by CBM International, HelpAge International, Sight Savers International, Task Force Sight and Life.
Table of Contents
1. Childhood Blindness Worldwide 2
2. Causes of Childhood Blindness 3
3. Onset of Blindness 4
4. Examination for Eye Disease in Children 5
5. Vitamin A Deficiency and the Eye 6
6. Symptoms and Signs of Xerophthalmia 8
7. Treatment of Xerophthalmia 10
8. Prevention of Xerophthalmia 12
9. Measles and Corneal Ulceration 14
10. Prevention and Treatment of Measles 15
11. Herpes Simplex Virus 16
12. Harmful Traditional Eye Medicines 17
13. Newborn Conjunctivitis 19
14. Treatment of Newborn Conjunctivitis 21
15. Corneal Ulceration 22
16. Corneal Scarring 25
17. Congenital Cataract 26
18. Causes and Investigation of Congenital Cataract 27
19. Surgery for Congenital Cataract 29
20. Congenital Glaucoma 31
21. Retinoblastoma 33
22. Retinopathy of Prematurity 35
23. Eye Injuries 37
24. Summary 39 Acknowledgments 41 1
1. Childhood Blindness Worldwide 600,000 39% Numbers of blind children 34% 500,000 400,000 21% 300,000 200,000 6% 100,000 0 Rich Middle Poor Very poor Standards of living and health care services How many children in the world are blind?
The exact number of children blind in the world is not known but it is estimated that the figure is approximately 1.4 million, with up to 500,000 new cases every year.
Many of these children die within months after they become blind.
The frequency and causes of blindness vary widely in different parts of the world: in Africa and parts of Asia, up to 15/10,000 children are blind, compared to 3/10,000 children in Europe and North America; nutritional factors and infections are more common in developing countries, whereas hereditary factors, developmental disease and the consequences of prematurity are more frequent causes in countries with better standards of living and health care services.
Much of the eye disease which can cause blindness can be either prevented or treated. Our task as health workers is to preserve healthy eyes and avoid the situation of the boy shown in the picture who has corneal scarring of both eyes and is blind, with all of adult life ahead of him. Also, we can seek to influence policy makers, advising them how improved health care can prevent eye disease.
What are the main causes of blindness in childhood?
Over a million children in Asia and Africa are blind and the single commonest avoidable cause is corneal scarring, due mainly to vitamin A deficiency. In Africa, corneal ulceration leading to corneal scarring is often associated with measles infection, and in Asia severe diarrhoea may lead to acute vitamin A deficiency causing blindness. Other causes of corneal scarring are conjunctivitis of the newborn (ophthalmia neonatorum), herpes simplex infection and the use of harmful (traditional) eye medicines. These causes are all preventable or treatable.
In many developing countries measles infection and vitamin A deficiency are being well controlled, and in these countries congenital and developmental cataracts are becoming relatively more important. Cataracts are a treatable cause of blindness in children.
In many middle income countries, particularly in Latin America and Eastern Europe, services for premature babies have expanded, and in many of these countries retinopathy of prematurity is the single commonest cause. This is a potentially preventable condition which can also be effectively treated.
In industrialised countries, inherited genetic factors causing cataract and retinal dystrophies are major causes of blindness in children, as are the consequences of premature birth. In industrialised countries the majority of children are blind from conditions which are not readily avoidable.
When do these eye conditions affect a child?
For the purpose of this teaching set we recognise that a child is aged 0-15 years.
A simple classification divides the causes of childhood blindness into four groups
depending on the time of onset of the condition leading to blindness:
1. Hereditary factors present from conception
2. Factors influencing the unborn child during pregnancy
3. Factors operating around the time of birth
4. Factors acting during childhood
5. Unknown Hereditary factors which contribute to childhood blindness may cause, for example, familial cataract or retinal dystrophies. Damaging influences to the unborn child during pregnancy include maternal infection with rubella and toxoplasmosis. Examples of factors affecting sight around the time of birth are the effect of too much oxygen given to the premature baby (retinopathy of prematurity) and infection (newborn conjunctivitis). Blindness occurring in childhood includes conditions due to vitamin A deficiency, measles, external eye infections, harmful traditional eye medicines and eye injuries.
44. Examination for Eye Disease in Children
A careful history should be taken, preferably from the mother who has had the closest contact with the child. Visual acuity should be assessed, and the findings recorded.
Children over the age of 5 years can usually be tested with a Snellen E chart (top left), but children younger than this need to use other tests, such as pictures or matching methods. In very young children, a history from the parents and observation of the infant can help in determining whether the child is blind or not.
In some children, eye disease will be immediately obvious although this will not always be the case. The cause of the eye condition may be due to infection (top right) which in this child was beginning to improve with intensive topical antibiotics.
In the variety of eye problems which present at your clinic the picture may be more complicated and difficult to treat. The child whose eye is shown bottom left is a young boy, aged 5, who had trachoma. The infective, inflammatory condition, caused by the organism Chlamydia trachomatis, had been made very much worse by treatment for two weeks with a harmful traditional medicine. The result was severe corneal scarring.
Some children will present with ‘quiet’ eyes but with considerable damage caused earlier in their lives. The boy pictured bottom right is blind due to dense corneal scarring, with distortion of the anterior parts of the eyes. A scarred, bulging anterior eye is called a staphyloma and is the result, in this case, of previous severe vitamin A deficiency. In children who are blind from conditions affecting their retina, optic nerve, or brain the front of the eyes appear entirely normal.
We shall now consider in more detail the common worldwide causes of blindness in children beginning with those leading to corneal scarring, all of which are preventable.
55. Vitamin A Deficiency and the Eye
Worldwide, vitamin A deficiency is the commonest single cause of blindness in children, accounting for an estimated 350,000 new cases each year. Vitamin A deficiency is also very important as it is associated with higher infant and childhood mortality rates, particularly associated with measles. It is estimated that 60% to 80% of children who become blind from vitamin A deficiency die within a few years because of increased susceptibility to infection and sometimes lack of care.
Recognition by health workers that vitamin A deficiency is causing blindness in children should also make them aware that children in these communities will be dying unnecessarily from a preventable cause. Health education for parents and communities is very important in preventing this nutritional disease.
Xerophthalmia is the term commonly used to describe an eye showing the clinical features of vitamin A deficiency. Literally, the term means ‘dry eye’ and one sign of xerophthalmia is the dry appearance of both the conjunctiva and the cornea, described as conjunctival and corneal xerosis. Vitamin A deficiency can also cause poor night vision due to lack of visual purple in the retina.
Vitamin A deficiency can occur for three major reasons:
• reduced intake of foods rich in vitamin A
• vitamins are not absorbed, usually because of diarrhoea
• increased need for vitamin A, as occurs during infections, particularly measles.
Blinding malnutrition is found in the developing countries of the world.
6 Which children are at risk of developing xerophthalmia?
While vitamin A deficiency can occur at any age, the group at risk of blindness is preschool age children, from 6 months to 6 years of age.
A typical child at risk of corneal blindness is a child who is one to 3 years old, no longer breast fed, who receives a poor diet and is malnourished, and who has developed measles (or another infection) or is suffering from diarrhoea. The child shown in the slide is malnourished and makes an unhappy picture - she is underweight, with obviously thin arms and legs. She has bilateral corneal ulceration due to vitamin A deficiency.
Measles is a particular risk factor in many countries and we shall look further at this important subject.
76. Symptoms and Signs of Xerophthalmia
What are the symptoms and signs of vitamin A deficiency affecting the eye?
The following are the ocular symptoms and signs of vitamin A deficiency (xerophthalmia). The World Health Organization clinical codes are given in brackets.
Night blindness (XN): Vitamin A is needed to replace rhodopsin (visual purple) in the retina at the back of the eye and this is necessary for night vision. An adult or older child, on questioning, will describe the problem of night blindness but a very small child will not be able to offer this information. Ask the mother if the child cannot see as well as other children in the evening.
Conjunctival xerosis (XIA): Vitamin A is required for the production of secretions on the surface of the eye. This dry appearance together with xerosis of the corneal epithelium gives the condition its name, xerophthalmia. There is damage to the cells that produce secretions which moisten the surface of the eye.
Bitot’s spots (XIB): A Bitot’s spot has a typical white foamy appearance and is localised on the surface of the conjunctiva. Bitot’s spots may be found in both eyes, most often on the temporal conjunctiva. The picture shown top left is one example of a Bitot’s spot. These may appear in children under 3 years but are more common in older children. The appearance indicates changes in the squamous epithelium of the conjunctiva with underlying xerosis.
Corneal xerosis (X2): The surface of the cornea can have a typical dry appearance, and this can be seen in the picture shown top right. This eye also has an ulcer (see below).
Corneal ulceration with xerosis (X3A): The eye pictured top right has an inferior corneal ulcer which has been stained green with fluorescein dye. This area of ulceration places this eye in the category, corneal ulceration with xerosis (X3A).
8 Corneal ulceration/keratomalacia (X3B): This is the consequence of severe vitamin A deficiency. The onset is often sudden, and the cornea may melt very quickly, even over a few hours (keratomalacia). This development is most often seen in young children. The child shown bottom left has deep corneal ulceration progressing towards keratomalacia.
Corneal scarring (XS): The significant end stage of malnutrition causing eye damage, in a child who survives, is corneal scarring (bottom right). Corneal scarring often has a marked effect on vision. The anterior part of the eye may bulge forward (anterior staphyloma) or the opposite may occur and the eye shrinks (phthisis).
It is important to realise that not every child who is vitamin A deficient and at risk of blindness will have obvious eye signs. Finding evidence of xerophthalmia in one child will indicate that other children in the same family and community are also vitamin A deficient, even if they have no obvious signs. A child may have just enough vitamin A but have very little reserve in the liver. If a child becomes ill with measles, for example, vitamin A stores in the liver are rapidly used up resulting in acute deficiency.
It is this situation that characteristically causes very rapid and severe corneal melting (keratomalacia) which results in blindness.
Learn to recognise the symptoms and signs of xerophthalmia. Not only will you save a child’s sight but you may also save a life.
How would you treat a child with symptoms or signs of vitamin A deficiency?
The World Health Organization recommends the following treatment schedule for children over one year old who have xerophthalmia.
• Immediately on diagnosis (Day 1) - 200,000 IU vitamin A orally†
• The following day (Day 2) - 200,000 IU vitamin A orally
• Four weeks later (Week 4) - 200,000 IU vitamin A orally † If there is vomiting, an intramuscular injection of 100,000 IU of water soluble vitamin A (not an oil-based preparation) may be used instead of the first oral dose.
If a child is under one year old or, at any age, weighs less than 8 kg: Use half the doses of the regimen given above.
• Immediately on diagnosis (Day 1) - 100,000 IU vitamin A orally
• The following day (Day 2) - 100,000 IU vitamin A orally
• Four weeks later (Week 4) - 100,000 IU vitamin A orally The third dose of vitamin A in both regimens may be given between one and 4 weeks if follow-up is likely to be uncertain.
A topical antibiotic eye ointment such as tetracycline 1% or chloramphenicol 1%, 3 times a day, is recommended to reduce the possibility of secondary bacterial infection of the eyes.
Carefully apply an eye pad to the eye, making sure the eyelids are closed under the eye pad. Do not press on the eye - there is always the danger of perforation if corneal ulceration is present.