Global Trends in Blindness and Vision Impairment Resulting from Corneal Opacity 1984-2020: A Meta-analysis

Abstract

Topic: We provide global estimates of the prevalence of corneal blindness and vision impairment in adults 40 years of age and older and examine the burden by age, sex, and geographic region from 1984 through 2020.

Clinical relevance: Corneal opacities (COs) are among the top 5 causes of blindness worldwide, yet the global prevalence, regional differences, and risk factors are unclear.

Methods: Abstracted data from the published literature and surveys were obtained from the Global Burden of Disease Vision Loss Expert Group. We supplemented this by an independent systematic literature search of several databases. Studies that provided CO vision impairment data based on population-based surveys for those 40 years of age or older were included, for a total of 244. For each of the 4 outcomes of blindness and moderate to severe vision impairment (MSVI) caused by trachomatous and nontrachomatous CO (NTCO), time trends and differences in prevalence by region, age, and sex were evaluated using a Poisson log-linear model with a generalized estimating equation method. Age-standardized estimates of global prevalence of blindness and MSVI were calculated using the 2015 United Nations standard populations.

Results: The global prevalence of blindness resulting from NTCO in those 40 years and older was 0.081% (95% confidence interval [CI], 0.049%-0.315%); that of MSVI was 0.130% (95% CI, 0.087%-0.372%). A significant increase with age was found (prevalence rate ratio, 2.15; 95% CI, 1.99-2.32). Latin America and Europe showed the lowest rates, with 2- to 8-fold higher rates of blindness or MSVI in other regions. The global prevalence of blindness resulting from trachomatous CO in those 50 years and older was 0.0094% (95% CI, 0%-0.0693%); that from MSVI was 0.012% (95% CI, 0%-0.0761%). Blindness resulting from trachomatous CO and MSVI increased with age and female sex, and rates were significantly higher in the African regions. A decrease in trachomatous blindness rates over time was found (prevalence rate ratio, 0.91; 95% CI, 0.86-0.96).

Discussion: An estimated 5.5 million people worldwide are bilaterally blind or have MSVI resulting from CO, with an additional 6.2 million unilaterally blind. Blindness resulting from trachomatous CO is declining over time, likely because of the massive scaleup of the global trachoma elimination program and overall socioeconomic development.

Financial disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Keywords: Blindness; Corneal opacity; Global; Trachoma; Vision impairment.

Figure 1

Map showing the countries within each region.

Figure 2

Bar graphs showing age-specific prevalences of (A) blindness and (B) moderate to severe vision impairment (MSVI) resulting from nontrachomatous corneal opacity (rates are per 10 000 people).

Figure 3

Bar graphs showing age-specific prevalences of (A) blindness and (B) moderate to severe vision impairment (MSVI) resulting from trachomatous corneal opacity (CO; rates are per 10 000 people). E = East; N = North; S = South; SE = Southeast.