Some eye diseases that lead to visual impairment can be prevented or the diseases themselves can be treated before they cause irreversible damage. However, the growth and ageing of the world's population has gone hand in hand with an increase in individuals with vision problems.
In order to highlight the need for effective prevention, the WHO (World Health Organisation) and the International Agency for the Prevention of Blindness in 1999 launched the an initiative called 'Vision 2020: The Right to Sight'. In 2013, the World Health Assembly also launched a new plan, 'Towards universal eye health: a global action plan 2014-2019'. These initiatives set a global goal:
All these studies are also collected in a database that is continuously updated, called the 'Global Vision Database'.
The main causes of blindness in the world
Cataracts and refractive errors were among the leading causes of blindness in 2020. Worldwide, it is estimated that more than 15 million adults over the age of 50 are blind due to cataracts, and more than 86 million people have reduced vision due to uncorrected refractive error. In essence, 50% of blindness globally in 2020 is due to one of these two diseases. The burden of total blindness due to cataracts and uncorrected refractive error has considerable regional variability, but is also present in high-income regions.
According to the Vision 2020 report, glaucoma, age-related macular degeneration and diabetic retinopathy are also among the causes of blindness in the world, contributing more than 6 million blind adults over the age of 50 and more than 13 million adults with severe vision loss. However, with the exception of diabetic retinopathy, the prevalence of blindness due to the listed diseases decreased between 1990 and 2020.
The vast majority of visual impairments caused by cataracts, refractive errors, diabetic retinopathy and glaucoma can be avoided with early diagnosis and timely intervention, which remain key to reducing their incidence.
Cataracts
In 2020, cataracts remained among the leading causes of blindness and severe vision loss in all regions of the world. Currently, it can only be treated by surgery, by appropriately qualified medical personnel, within healthcare facilities that are suitable to perform surgery and manage any postoperative complications. Since the prevalence increases with age and is higher in women than in men, combating this disease is also an important goal in terms of equal opportunities and gender equity. Screening has been shown to improve access among less affluent groups, such as women and the elderly. Therefore, the development of robust eye care systems, integrated with population awareness campaigns, is necessary.
Refractive errors
They are a major cause of vision problems, but are also easily treated with glasses, contact lenses or surgery. Myopia, hypermetropia and astigmatism are among the main causes of disability in distance vision. Uncorrected aphakia has significantly decreased since 1990 due to the use of intraocular lenses during cataract surgery. In contrast, the prevalence of myopia is increasing rapidly, especially in urban areas.
Glaucoma
It has been ranked as the second leading cause of blindness and the fourth leading cause of severe vision loss worldwide. After diagnosis, treatment for glaucoma can halt or slow the deterioration of vision in most patients. Hence, the importance of improving surveillance systems, highlighting the risk among family members and providing effective treatment.
Age-related macular degeneration
The prevalence of blindness due to this disease decreased by almost 30% from 1990 to 2020. This decrease was probably associated with the clinical introduction of anti-VEGF therapy for exudative age-related macular degeneration. However, most patients with macular degeneration show the currently untreatable non-exudative form, which can progress to geographic atrophy.
Diabetic retinopathy
It is the only cause of blindness that has shown a global increase in prevalence between 1990 and 2020. People with diabetes are living longer and longer and are expected to reach 600 million by 2040. Consequently, there will likely be an increase in people with diabetic retinopathy. This is of particular concern in younger and economically active age groups because, compared to cataracts and refractive errors, the management of severe diabetic retinopathy requires a far greater amount of resources, including the availability of ophthalmologists trained in laser and surgery.
Blindness in the last 30 years
Analysis of the past 30 years has shown that the prevalence of avoidable visual impairment has decreased in adults aged 50 years and older over the past decade, but has not achieved the targeted reduction of 25% outlined in the WHA's global action plan. The main reason, from a global perspective, is the inability of eye care services to keep pace with an ageing and growing population. However, the reduction in the age-standardised prevalence of blindness due to causes such as cataracts, glaucoma, age-related macular degeneration and refractive errors is reassuring and a change in the right direction.
The report also highlighted areas requiring special attention, such as diabetic retinopathy, which was found to be the only cause of increased prevalence of blindness over three decades.
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Dr. Carmelo Chines
Direttore responsabile
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