Myopia, or nearsightedness, has become increasingly common among children globally. This condition is a refractive error where light entering the eye focuses in front of the retina instead of directly on it, which causes distant objects to appear blurry. Myopia typically occurs because the eyeball has grown too long, a change called axial elongation. This rapid and widespread increase in the number of children needing vision correction has prompted researchers to investigate the modern environmental and behavioral factors driving this shift.
The Global Reality of Increasing Myopia Rates
The increase in nearsightedness represents an accelerating epidemiological shift worldwide, not simply better detection. Global prevalence among children has risen significantly, from an estimated 24.32% in 1990 to 35.81% in 2023, with projections suggesting nearly 40% of the world’s children could be myopic by 2050. This trend is particularly pronounced in East Asia, where prevalence rates in teenagers and young adults can exceed 80% in some regions.
While genetics play a role by predisposing some individuals to the condition, heredity alone cannot explain the rapid increase seen in recent decades. The rate of change strongly implicates widespread shifts in lifestyle and environment as the primary drivers. High levels of myopia increase the long-term risk of sight-threatening conditions, such as glaucoma and retinal detachment.
The Environmental Factor: Lack of Outdoor Light
One of the most significant factors identified is the reduction in time children spend outdoors exposed to natural light. Research indicates that outdoor time has a protective effect against the onset of myopia, independent of the amount of close-up work performed. This protection is linked to the high intensity of natural light, which is far brighter than typical indoor lighting.
Exposure to bright light stimulates the release of dopamine within the retina. This naturally occurring neurotransmitter acts as a signal to the eye, helping to regulate its growth and prevent the excessive elongation of the eyeball. When children spend most of their time indoors, the eye does not receive the necessary light signal to keep its growth in check.
To achieve this protective benefit, vision experts recommend that children aim for a minimum of 90 to 120 minutes of outdoor time daily. This time does not need to involve vigorous activity; simply being outside during daylight hours provides the necessary light exposure. Even on overcast days, the light intensity outdoors is generally sufficient to trigger the biochemical pathways that support healthy eye development.
The Behavioral Shift: Sustained Near Work
The second major contributor is the increase in sustained near work, which includes intensive reading, studying, and the use of digital devices. Prolonged focus on objects held close to the face requires the eye’s focusing muscles to work harder, which can induce eye strain.
When the eye focuses on a near object, it often exhibits a phenomenon called “accommodative lag,” where the focus falls slightly behind the retina. For a developing eye, this consistent, imprecise focus may act as a signal that encourages the eyeball to grow longer to bring the image into sharp focus, thereby contributing to myopia development.
To mitigate the effects of this visual stress, a behavioral modification technique known as the 20-20-20 rule is recommended. This rule advises that for every 20 minutes spent focusing on a close object, a person should take a 20-second break and look at something at least 20 feet away. Regular breaks allow the focusing muscles in the eyes to relax, helping to prevent the excessive strain associated with continuous close-up viewing.
Modern Approaches to Managing Myopia
For children who have already been diagnosed with progressive myopia, modern management strategies are used to slow the rate of vision deterioration, not just to correct it. These interventions aim to control the axial elongation of the eyeball.
One widely used treatment is low-dose Atropine eye drops, typically administered in concentrations between 0.01% and 0.05%. The drops are thought to slow progression by modulating biochemical pathways within the eye that govern growth.
Specialized contact lenses that utilize peripheral defocus are another effective option. These include soft multifocal contact lenses and Orthokeratology (Ortho-K) lenses. Ortho-K involves wearing rigid lenses overnight that temporarily reshape the cornea, gently flattening it to correct vision during the day.
Both Ortho-K and multifocal lenses are designed to create a specific pattern of light focus, known as myopic peripheral defocus, on the retina. This peripheral defocus is believed to reduce the signal that prompts the eye to grow longer. Combining these optical treatments with low-dose Atropine has been shown to offer superior control in slowing the eye’s axial growth for some children.