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In tropical countries, it is estimated that 25 million people are blind from preventable causes and of those, trachoma is the most important, contributing to approximately 4% of global blindness.[1] Trachoma is a very common chronic conjunctival infection caused by Chlamydia trachomatis, which is transmitted by flies or through close personal contact. (Note that the organism involved is C. trachomatis serotype A-C; C. trachomatis serotypes D-K are associated with genital infections and only occasionally cause a chronic follicular conjunctivitis that is clinically indistinguishable from trachoma[2]).
Other causes of preventable blindness include:

  • Xerophthalmia, due to lack of vitamin A in the diet.
  • Onchocerciasis, or river blindness, an infection of the skin by filarial larvae that may also affect the conjunctiva of the eye.
  • Trachoma is the second most common cause of blindness in the world and the most common infective cause. The World Health Organisation (WHO) is aiming to eliminate trachoma as a blinding disease by 2020.[1, 3]
  • It was once endemic in most countries but now is confined to Africa, Asia, the Middle East and Aboriginal communities in Australia, as shown on the WHO map.[4]
  • There are an estimated 84 million people affected worldwide with 8 million visually impaired and 3.4 million blind.[5]
  • There is no racial predilection, only a predilection for poverty and poor personal hygiene.
  • Women are affected 2 to 4 times as often as men but pre-school children of both genders are equally affected.
  • In hyperendemic areas active disease is most common in pre-school children with prevalence rates as high as 60-90%, most commonly aged 3-5 years old.[6]
  • Where community prevalence decreases to around 20%, active disease is clearly seen to cluster in families.[2]
  • It is currently responsible for more than 3% of the world's blindness but the number keeps changing due to the effect of socio-economic development and current control programmes for this disease.

Transmission is mostly between children and the women who care for them (disease of the crèche); this accounts for the higher prevalence in women. Blindness does not ensue until middle age: repeated episodes of infection cause chronic follicular conjunctival inflammation (active trachoma), leading on to the cicatricial stage of tarsal conjunctival scarring, entropion, trichiasis (in-turning of the eyelashes) which leads to corneal scarring and opacity.

There are various stages of the disease that are described below; the references in this section link to pictures provided by the WHO:

  • Follicular trachoma (Grade TF) produces active follicles on the upper tarsal conjunctiva. This phase of the disease is relatively asymptomatic.
  • Inflammatory trachoma (Grade TI) causes thickening of the upper tarsal conjunctiva, which obscures more than half of the normal tarsal vessels and can produce significant conjunctival scarring and blindness. [7]
  • Trachomatous scarring (Grade TS) produces easily visible scarring in the upper tarsal conjunctiva.[8] Although this may not cause direct symptoms per se,
  • Trichiasis (Grade TT) is when eyelashes touch the globe causing fibrosis and corneal opacification. Some vision can be restored with successful correction of trichiasis.[9]
  • Corneal opacity (Grade CO) is defined as one that is easily visible and obscures at least part of the pupillary margin.[10]

Laboratory tests are not used in endemic areas where the clinical appearance is enough.

  • Cell culture used to be the standard test but has been superseded by newer tests.
  • In other areas, polymerase chain reaction (PCR) and ligase chain reaction (LCR) have high sensitivity and specificity.
  • Another new test is direct fluorescein-labeled monoclonal antibody (DFA) and enzyme immunoassay (EIA) of conjunctival smears.
  • Giemsa cytology (the finding of intracytoplasmic inclusions) is technically demanding, has a high specificity but low sensitivity.

The World Health Organisation (WHO) has implemented a policy of prevention known by the mnemonic SAFE:[11]

  • S urgery for trichiasis
  • A ntibiotics, especially azithromycin to eradicate infection
  • F acial cleansing and attention to hygiene
  • E nvironmental improvement

To turn to each:

  • Eyelid surgery can prevent corneal scarring and blindness. As an interim to prevent entropion, double-sided sticking plaster has been used to good effect.[12]
  • Oral azithromycin (1 gm po or 20 mg/kg in children, stat[3] then repeated every 6-12 months[1]) is the antibiotic of choice and if a child is infected the whole family should be treated. Topical tetracycline and polymixin is as effective as oral azithromycin.[13] The latter is a shorter course and associated with few side-effects (which are mild) but is more expensive (although large donation programmes are in place[1]). Even a single dose of azithromycin causes a marked fall in prevalence and intensity of the disease in a mass programme and it was sustained for 2 years.[14] A single dose of azithromycin is as effective as 6 weeks of topical tetracycline. Topical antibiotics are less useful long-term as C. trachomatis occurs in the oropharynx and patients may re-infect themselves.[2] Mass treatment programmes of entire communities may be necessary where the prevalence in 1-9 year old children exceeds 10%[2] but this has to be balanced with the possibility of antimicrobial resistance (not a problem to date).[15]
  • Community-based health promotion about facial cleansing and hygiene reduces the risk and severity of trachoma.[16] Do not let flies walk over children's eyes.
  • Environmental health involves personal hygiene as well as clean water and safe sewage disposal along with a reduction in flies.

This SAFE approach has been shown to be successful in a number of countries.[17] Researchers have highlighted the need to focus management on children in order to tackle the problem in its early stages.[18]

Appropriate treatment of early disease gives an excellent prognosis. Severe disease may be stabilised but vision may not improve. Re-infection worsens the prognosis.

Further reading and references

  1. Mathew AA, Turner A, Taylor HR; Strategies to control trachoma. Drugs. 200969(8):953-70. doi: 10.2165/00003495-200969080-00002.

  2. Solomon AW, Ringland Taylor H; eMedicine: Trachoma (September 2007)

  3. Denniston AKO, Murray PI; Oxford Handbook of Ophthalmology, Oxford University Press, 2009

  4. World map showing distribution of Trachoma, World Health Organization, 2005

  5. Fact sheet, Trachoma; World Health Organization

  6. World Health Organisation; Trachoma grade TF

  7. World Health Organisation; Trachoma grade TF + TI

  8. World Health Organisation; Trachoma grade TS

  9. World Health Organisation; Trachoma grade TT

  10. World Health Organisation; Trachoma grade CO

  11. Bailey R, Leitman T; The SAFE strategy for the elimation of trachoma by 2020: Will it work? Bulletin of the World health Organisation 2001

  12. Yorston D, Mabey D, Hatt SR et al.; Interventions for trachoma trichiasis. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD004008. DOI: 10.1002/14651858.CD004008.pub2

  13. Dawson CR, Schachter J, Sallam S, et al; A comparison of oral azithromycin with topical oxytetracycline/polymyxin for the treatment of trachoma in children. Clin Infect Dis. 1997 Mar24(3):363-8.

  14. Solomon AW, Holland MJ, Alexander ND, et al; Mass treatment with single-dose azithromycin for trachoma. N Engl J Med. 2004 Nov 4351(19):1962-71.

  15. Ray KJ, Lietman TM, Porco TC, et al; When can antibiotic treatments for trachoma be discontinued? Graduating communities in three african countries. PLoS Negl Trop Dis. 2009 Jun 163(6):e458.

  16. West S, Munoz B, Lynch M, et al; Impact of face-washing on trachoma in Kongwa, Tanzania. Lancet. 1995 Jan 21345(8943):155-8.

  17. Yayemain D, King JD, Debrah O, et al; Achieving trachoma control in Ghana after implementing the SAFE strategy. Trans R Soc Trop Med Hyg. 2009 Mar 13.

  18. Taylor HR; Elimination of blinding trachoma revolves around children. Lancet. 2009 Mar 28373(9669):1061-3.