Natural history of trachomatous scarring in The Gambia - Results of a 12-year longitudinal follow-up

Purpose: The sight-threatening complications of trachoma are trichiasis and corneal opacity, and these remain the world's most common cause of prevent able blindness. The aim of the study was to investigate the rate of progres sion of trachomatous conjunctival scarring to trichiasis and corneal opacit y and to investigate risk factors for such progression. Design: A 12-year, longitudinal study of the incidence and risk factors for the development of trichiasis and corneal opacity in a cohort of patients initially identified with trachomatous scarring in The Gambia. Participants: Six hundred thirty-nine subjects with some degree of trachoma tous scarring were identified from the 1986 survey, and attempts were made to trace all these subjects. Methods: Successfully traced subjects were interviewed, examined, and grade d for trachoma. Main Outcome Measures: (1) Twelve-year rates of progression. (2) Risk facto rs for progression of disease. Results: Three hundred twenty-six of six hundred thirty-nine (51%) subjects were traced and examined, 108 (17%) had died, and 205 (32%) were lost to f ollow-up. After 12 years, 6.4% (95% confidence interval [CI], 4.0-9.97) of scarred subjects had trichiasis develop, 5.96% (95% CI, 3.67-9.42) had corn eal opacity develop, 16.51% (95% CI, 12.71-21.13) had visual impairment/bli ndness develop, and 2.5% (95% CI, 1.2-5.0) had corneal visual impairment/bl indness develop. Mandinka ethnicity was a risk factor for trichiasis (odds ratio [OR], 4.3; 95% CI, 1.3-14.4), and trichiasis at baseline was a risk f actor for corneal opacity (OR, 8.4; 95% CI, 1.8-39.2). History of lid surge ry for trichiasis was associated with corneal opacity at follow-up (OR, 4.4 ; 95% CI, 1.4-14.0). Older age was a significant risk factor for developmen t of trichiasis, corneal opacity, and visual loss (OR, 1.07; 95% CI, 1.01-1 .12). Bilateral cataract was present in 40% of traced subjects and was asso ciated with the incidence of visual impairment/blindness (OR, 9.4; 95% CI; 4.5-19.6) Conclusions: This is the first study to demonstrate the link between trichi asis and future corneal opacity, and it provides the rationale for performi ng lid rotation surgery on patients with trichiasis who do not yet have cor neal opacity. The association between corneal opacity at follow-up and prev ious surgery among trichiasis patients suggests late presentation as a prob lem. The planning of surgical services will be aided by the incidence figur es generated by this study. (C) 2001 by the American Academy of Ophthalmolo gy.