[Incidence and causes of visual impairment in the district of Mahdia, in east Tunisia: Retrospective study of 1487 cases].

Objective: To study socio-demographic characteristics and main causes related to visual impairment (VI) as a function of age bracket and to analyze their trends over time in the district of Mahdia.

Method: A retrospective review was performed on 1487 cases of visual impairment registered with the social authorities in Mahdia, between 1980 and 2013. The social, demographic, vision exam findings and causes were ascertained and analyzed in an SPSS database. Incidence rates of VI and blindness due to various causes were calculated based on the demographic data from the NSI to estimate the time trends using the general linear regression model and Spearman correlation.

Results: Analyses included 1487 participants with a median age of 47 years, 40.6% of cases were aged under 45 years. Children accounted for 11.1% (165 patients), while age was between 16 and 45 years in 29.5% (439 patients), between 46 and 65 years in 31.5% (469 patients) and greater than 65 years in 27.8% (414 patients). The sex-ratio (M/F) was 1.78. Socially, 51% came from rural areas, 62% were illiterate, and 84% were unemployed. We observed blindness in 70% of participants and low vision in 30%. In children, the causes were dominated by congenital cataract and congenital glaucoma, each present in 31 children (18.8%). Between 16 and 45 years, glaucoma and hereditary dystrophies of the retina were found in 62 and 61 patients respectively (14% each). For age between 46 and 65 years, trachoma was responsible for 19.8% of cases of VI, glaucoma in 15.8% and cataract in 15.1%. Beyond 65 years, glaucoma accounted for 30.7% of the causes of VI and cataract 27.8% of cases. Trend analysis shows a significant increase in the incidence rate of visual impairment with an average of 12% per year (P=0.001). The mean age increased by 46% (P=0.003). Trachoma increased by 118% (P<0.0001) between 1980 and 1990, then declined by 42% (P=0.0013) between 1991 and 2013. Incidence of VI significantly increased by 4% for cataract (P=0.001), 23% (P=0.001) for glaucoma and 20% (P=0.02) for diabetic retinopathy, while VI related to refractive errors and AMD showed no significant change.

Conclusion: Advanced age, lower educational and socio-economic status were associated with bilateral VI. Age related eye problems are the main causes of VI, and their incidence is tending to increase. Public health policies and procedures should be targeted to risk related populations and age-related diseases in order to control the incidence of visual impairment and avoid its consequences.