Visual impairment and blindness represent a substantial global public health challenge, impacting millions across all ages and regions. Understanding the extent of this issue involves appreciating how vision loss is categorized and quantified. The total number of people affected worldwide reflects demographic shifts and the prevalence of specific eye conditions.
Understanding Visual Impairment Categories
Classifying visual impairment is important for consistent data collection and public health initiatives. International health organizations, such as the World Health Organization (WHO), define levels of vision loss based on visual acuity, which measures how clearly a person sees.
This classification distinguishes blindness from moderate to severe visual impairment (MSVI), characterized by visual acuity worse than 6/18 but equal to or better than 3/60. Mild visual impairment is defined by visual acuity worse than 6/12 to 6/18. Near vision impairment, such as presbyopia (presenting near visual acuity worse than N6 at 40 cm), further refines these categories.
Global Prevalence of Blindness
Globally, at least 2.2 billion people currently experience either near or distance vision impairment. Approximately 1 billion of these cases could have been prevented or remain unaddressed with existing interventions.
Current estimates indicate that 43 million people worldwide are blind. An additional 295 million live with moderate to severe visual impairment, while 258 million have mild visual impairment. Furthermore, 826 million people are affected by presbyopia, a common near vision impairment.
Vision impairment disproportionately affects certain demographic groups. More than 80% of individuals experiencing vision impairment are aged 50 or older. Women also represent a slight majority of those with vision loss, accounting for approximately 55% of both blind individuals and those with moderate to severe visual impairment. The prevalence of distance vision impairment in low- and middle-income regions is estimated to be four times higher than in high-income regions.
Key Contributing Factors
Uncorrected refractive errors and cataracts stand as the two most common causes of vision impairment and blindness globally. Refractive errors, which include conditions like nearsightedness or farsightedness that can be corrected with eyeglasses or contact lenses, are the leading cause of visual impairment. In 2020, uncorrected refractive errors were responsible for 3.7 million cases of blindness and 157 million cases of moderate to severe visual impairment.
Cataracts, characterized by the clouding of the eye’s lens, are the leading cause of blindness worldwide. These account for approximately 15.2 million cases of blindness among individuals aged 50 and older in 2020. Other significant contributors to global vision loss include age-related macular degeneration (AMD), which affected about 1.8 million people with blindness and 6.23 million with moderate to severe vision impairment in 2020.
Glaucoma, a condition that damages the optic nerve, and diabetic retinopathy, a complication of diabetes, also contribute substantially to vision impairment. In 2020, glaucoma caused blindness for 3.6 million people aged 50 and older, while diabetic retinopathy affected 0.86 million in the same age group. Trachoma, an infectious eye disease, has seen a significant reduction in prevalence over the past two decades due to control efforts.
Shifting Global Landscape
The number of people living with visual impairment is projected to increase significantly in the coming decades. Overall vision impairment is expected to rise from 1.1 billion people in 2020 to 1.8 billion by 2050. Specifically, the number of individuals living with blindness is predicted to grow from 43 million in 2020 to 61 million by 2050.
This anticipated increase is primarily driven by global population growth and the aging of populations worldwide. As people live longer, they are more likely to develop age-related eye conditions that lead to vision loss. While the age-standardized prevalence rate of blindness decreased by 28.5% between 1990 and 2020, the absolute number of people affected still rose due to these demographic shifts.
Regional disparities in visual impairment are expected to persist, with prevalence rates in poorer regions remaining considerably higher than in high-income areas. These trends highlight a growing need for enhanced eye care services and interventions globally.