Myopia, often called nearsightedness, makes distant objects appear blurry while close-up items remain clear. This occurs when the eye focuses images in front of the retina instead of on it, either because the eyeball has grown too long (axial myopia) or the cornea is too curved. While genetics are a known factor, researchers are now investigating environmental influences, particularly the role of light exposure in the eye’s development and the progression of nearsightedness.
The Role of Natural Light in Myopia Prevention
Evidence connects time spent outdoors with a reduced risk of myopia in children, an effect linked to the intensity of natural light. The leading hypothesis is that high light intensity stimulates the release of dopamine in the retina. This neurotransmitter then acts as a signal to inhibit the excessive axial elongation of the eyeball, a primary cause of myopia.
The difference in light intensity between environments is stark. A bright, sunny day can provide over 100,000 lux (the unit of illuminance), while a well-lit indoor room may only offer around 500 lux. Even on an overcast day, outdoor light levels far surpass what is experienced inside.
The amount of time spent in this high-intensity light is directly related to the preventative benefit. Studies suggest that for every additional hour children spend outdoors per week, their risk of developing myopia can decrease.
Indoor Lighting and Myopia Development
Concerns have been raised about whether artificial light from fluorescent or LED bulbs could contribute to nearsightedness. However, current scientific evidence does not support the idea that a specific type of indoor light is inherently harmful to eye development in this way.
Instead, the focus has shifted to light intensity. The lower lux levels indoors fail to provide the dopamine-releasing stimulus that natural light offers. The problem appears to be the absence of intense brightness found outdoors, not the presence of artificial light itself.
Indoor environments are also where prolonged near-work, such as reading and using digital screens, occurs. This sustained focus on close objects is another established risk factor for myopia. This creates a combination of low light intensity and high levels of near-work, conditions conducive to myopia development.
Red Light Therapy as a Myopia Treatment
Distinct from prevention, red light therapy is a treatment to slow the progression of existing myopia. This approach, called repeated low-level red-light (RLRL) therapy, involves a patient looking into a device that emits red light at a specific wavelength, usually around 650 nanometers (nm). The treatment typically lasts for a few minutes at a time, twice a day.
The proposed mechanism is that red light penetrates the eye to stimulate the choroid, a layer of tissue between the retina and sclera. This stimulation is thought to increase blood flow and thickness in the choroid. This may in turn reduce the scleral thinning and stretching that leads to axial elongation.
Clinical studies report a significant reduction in myopia progression in children undergoing the treatment. However, RLRL therapy is an area of ongoing research and not yet a standard of care, with questions about long-term safety. This treatment must be administered under the supervision of an eye care professional.