We studied five different tests for diagnosing conjunctival Chlamydia trachomatis infection in specimens obtained from 100 children with moderate-to-severe trachoma. The tests were Giemsa stain, isolation in cell culture, direct fluorescein-conjugated monoclonal antibody, enzyme immunoassay, and a DNA probe. The Giemsa stain was least sensitive at 29%. The other tests gave essentially equivalent performances: sensitivity ranged from 73% to 84% and specificity from 93% to 100%. Seven of the 45 positive specimens were only positive in cell culture, whereas 11 of the 45 were negative in culture but positive in at least two nonculture tests. We speculate that these discordant results actually reflect the biologic status of the chlamydial infection. There appears to be a stage in the infection where chlamydial antigens and nucleic acids can be detected in the absence of infectivity. This stage of infection may contribute to the pathogenesis of trachoma by providing a source of sensitizing antigen.

SUMMARY A population based survey of trachoma and blindness was conducted in a rural Nile Delta hamlet. Trachoma remains hyperendemic in this region. Active trachoma was common among preschool children; over half had moderate to severe disease. Of residents 25 years old 90% had substantial conjunctival scarring. Severe conjunctival scarring was commoner among women (84%) than men (58%), and three-quarters of older women had trichiasis/entropion compared with 57% of older men. Males and females had equivalent age specific rates of inflammatory disease. Blindness was associated with old age; 17% of residents aged 50 and over were blind. Estimates of blindness based on this survey and other surveys in Egypt indicate that blindness is still a serious public health problem in rural Egypt. The number of blind persons in Egypt will increase from an estimated 420 000 in 1980 to 868 000 by the year 2020. The current crude blindness rate of 1.8% is expected to increase to 2-3% in the year 2000 and to 3-2% in 2020.As a part of an effort to develop a comprehensive approach to preventing blindness in Egypt we assessed the magnitude of trachoma and trachoma induced blindness in a rural community in the Nile Delta. The survey included environmental characteristics and behavioural observations. Trachomatous inflammatory disease of the conjunctiva is characterised by the presence of follicles and papillary hypertrophy. Extension of blood vessels (pannus) over the cornea and conjunctival scarring are manifestations of chronic disease in susceptible individuals. Scarring of the conjunctiva produced by chronic inflammation during childhood causes the eyelids to deviate inward (trichiasis/ entropion) long after the inflammatory disease has subsided. Constant abrasion of the eye by eyelashes causes corneal scarring and loss of vision in adult life.Trachoma is considered to be the world's leading cause of preventable blindness. An estimated 500 million people have trachoma, with six million blind. '

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THE PREVALENCE rate of blindness in a community may be taken as an index of the progress of such a community since it, as well as the individual person, bears responsi-bility for visual care. Education, habits, beliefs, and socioeconomic standards are all factors which determine the importance that a person attaches to his vision and, hence, the degree of care that he gives his eyes. The community also must provide healthy surroundings and attempt to induce good habits throughi hiealth education Dr. Said is professor and chairman of the department of ophthalmology and principal investigator of the blindness register survey; Dr. Korra is assistant professor of ophthalmology and project control officer; Dr. El-Kashlan is assistant professor of hygiene and public health at Tanta; aU three are members