Comm Eye Health Vol. 17 No. 52 2004 pp 60. Published online 01 December 2004.

The evidence base for trachoma interventions

Richard Wormald

Co-ordinating Editor, Cochrane Eyes and Vision Group (CEVG), International Centre for Eye Health, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT.

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SAFE is a policy based on common sense and practical know-how. It includes all the things we know contribute to blindness from the disease and the strategy is to interrupt the pathway to sight loss at several different stages.

It is, however, worth examining the evidence which underlies this policy. Like so often in politics and planning, policies are made first and then evidence is sought to support them afterwards. This is not a strictly evidence based approach.

There are Cochrane reviews either underway or published on all four components of SAFE.

Surgery for trichiasis

Trichiasis is one of the most important components of the blinding process. That something has to be done about abrading lashes is without doubt. However, there have been no trials on whether surgery is more effective than simple epilation, though epilation has been found less effective than using tape to pull the lashes away from the globe. Another, perhaps more important, question is which operation is the most effective, simplest and cheapest to perform with the least complications.

A Cochrane review will soon be published addressing these questions but needless to say, like is so often the case, there are few good quality studies which adequately address this question.

Other important questions are about measures to improve uptake of surgery – can the operation be safely performed in the community and can paramedical staff be successfully trained to do the surgery. These questions are included in the systematic review which will soon be published in the Cochrane library.

Antibiotics for active trachoma

A Cochrane review has been published for two years on this question and is currently being updated. Despite the growing confidence in the safety and effectiveness of azythromycin, there are few trials addressing the question and none show a convincing advantage over existing treatments. This reflects the nature of the studies and the difficulty in conducting large trials on at-risk communities. Before and after studies such as the one recently published in the New England Journal of Medicine (abstracted on page 61) provide such convincing evidence of effectiveness that it may now be difficult to ethically conduct new trials. It is a shame that these trials have not been conducted since studies without a comparator group mean that the effect size cannot be estimated. We can only know that treatment is effective but not by how much. This also makes it difficult to build models of cost-effectiveness.

More evidence is needed however. Dosage, frequency, targeted versus mass treatment, means of distribution, safety monitoring and resistance are questions highlighted in an important Lancet review last year (Kuper H, Solomon AW, Buchan J, Zondervan M, Foster A, Mabey D. A critical review of the SAFE strategy for the prevention of blinding trachoma. Lancet Infect Dis. 2003 Jun;3(6):372-81. Abstract included in Issue 49 of the Community Eye Health Journal).

Face washing

Improved personal hygiene and regular washing of the hands and face of children are common sense interventions which are hard to evaluate in trials. Two have been found by reviewers who published a review on the Cochrane library last year on this subject. One was a randomised controlled trial in which three villages were randomised to separate interventions while another previously unpublished trial was found in which children were individually allocated to topical tetracycline, face washing, face washing and tetracycline, and no treatment. Neither of these studies demonstrated convincing evidence of effectiveness. Clearly more research is needed in this area.

Environmental interventions

A Cochrane review on this topic will shortly be published. Out of 285 citations, only one trial addressing this issue in the form of a cluster randomised controlled trial was found. Some indication that health education may have some impact was found in this study but no other studies were found answering questions on the many other potential environmental interventions including latrines, fly control, water supply and garbage disposal.

The Lancet review concluded that much more research is needed to reinforce the SAFE strategy on all aspects but especially in interventions for facial cleanliness and environmental improvement. These latter may be as effective as expensive antibiotics and have the advantage of improving many other aspects of quality of life.