Refractive errors are the most common vision problems worldwide, affecting how the eye focuses light onto the retina. These conditions, including myopia (nearsightedness) and hyperopia (farsightedness), are caused by variations in the shape of the eyeball or the cornea. Understanding which condition is more prevalent globally is important for public health planning and addressing vision impairment.
Understanding Myopia and Hyperopia
Myopia, or nearsightedness, occurs when the eye focuses an image in front of the retina rather than directly on it. This happens because the eyeball is slightly too long or the cornea is too steeply curved, giving the eye too much focusing power. Distant objects appear blurry, though vision for close-up tasks remains clear.
Hyperopia, or farsightedness, is the opposite condition, where the eye focuses the image behind the retina. This error is caused by an eyeball that is too short or a cornea that is too flat, resulting in insufficient focusing power. People with hyperopia generally see distant objects more clearly, but they experience strain or blurriness when focusing on objects up close. Both conditions are correctable using concave lenses for myopia and convex lenses for hyperopia.
Global Prevalence: Which Condition Dominates?
Myopia (nearsightedness) is significantly more common globally than hyperopia (farsightedness), leading public health experts to label it a worldwide “myopia epidemic.” Estimates indicate that myopia affected approximately 1.4 billion people in 2000, representing nearly 23% of the world’s population. This dominance has accelerated in the 21st century.
Projections suggest this trend will continue, with approximately 5 billion people (nearly half the world’s population) expected to have myopia by 2050. The increasing rates are attributed to environmental factors, specifically increased time spent on near-work activities and decreased time outdoors during childhood. This lifestyle shift, particularly in urbanized populations, drives myopia’s global dominance. Higher degrees of nearsightedness are associated with increased risk for sight-threatening conditions like retinal detachment.
How Refractive Error Prevalence Shifts Across the Lifespan
The prevalence of both conditions shifts significantly over a person’s lifetime. Most infants and young children are born slightly hyperopic (farsighted), which is normal for a developing eye. As the eye grows, this mild hyperopia often decreases naturally, typically resulting in clear vision by early childhood.
Hyperopia is more common than myopia in the youngest age groups, but this balance shifts as children enter school age and adolescence. Near-work activities during these years contribute to eye lengthening, driving the surge in myopia cases that peak in young adulthood. Presbyopia, the age-related loss of the eye’s ability to focus on close objects, becomes universal after age 55, though it is a loss of lens flexibility rather than a static refractive error.