Differences in the severity of physical signs in the right and left eyes of patients with trachoma in Syria and Burma

A field record card to permit the recording of physical signs separately in the two eyes, in cases of trachoma was produced by WHO in 1967. The card was used to record clinical examinations in a controlled trial in Syria in 1967 and in the running assessment of a trachoma control programme in Burma in 1968-69.Differences in physical signs in the two eyes were observed in over 20% of cases in Syria and over 35% of cases in Burma. Even when limited to the same stage of infection, differences between the two eyes in the same individual are in the order of 10%. Limiting the examination to one eye underestimates prevalence and severity and overestimates changes in the disease pattern with time; a combined reading for both eyes should give a more accurate picture of infection. A computer could be used in special studies to free the observer from the need to make subjective judgements concerning the more severely affected eye.