Outdoor Activities Aid Myopia Prevention in Adolescents

Time spent outdoors is a key factor influencing the onset and progression of myopia. Numerous studies have shown that increased outdoor activity can significantly help prevent myopia or slow its progression. Evidence suggests that outdoor activities effectively slow refractive changes in both myopic and non-myopic children. Increasing outdoor activity time is central to myopia prevention strategies and a crucial component of myopia control plans.

Research has identified several actions that help in myopia control, such as increasing brightness, reducing peripheral defocus, raising vitamin D levels, exposure to light closer to the natural spectrum, more physical activity, a well-regulated day-night rhythm, less near work, and higher spatial frequency. Outdoor activities enhance vitamin D levels and light intensity, boosting dopamine release and blood flow in the retina, which supports sustained blood flow in choroid and retinal tissues. The contrast between indoor and outdoor light intensity is notable, as outdoor sunlight can reach up to 100,000 to 200,000 lx, while indoor lighting is usually limited to less than 1,000 lx. Under strong outdoor sunlight, the pupils naturally constrict, increasing depth of field and slowing the progression of myopia while reducing the light entering the eyes, thereby protecting the retina.

Potential Eye Damage from Outdoor Activities

The primary risk factor for eye tissue and visual function damage during outdoor activities is ultraviolet (UV) radiation. UV rays are divided by wavelength into three types: UV-A (315-400nm), UV-B (290-315nm), and UV-C (100-290nm). As UV radiation passes through the atmosphere, UV-C and around 90% of UV-B rays are absorbed by the ozone layer. Therefore, the UV radiation reaching the Earth's surface mainly consists of UV-A and a small amount of UV-B. Exposure to UV radiation is a known risk factor for eyelid malignancies (basal cell carcinoma and squamous cell carcinoma), photokeratitis, climate-induced droplet keratopathy, pterygium, cataracts, macular degeneration, and other retinal conditions. Over time, the risk of these conditions increases. 

Factors that influence UV-induced eye damage include wavelength, light intensity, and exposure duration. Shorter-wavelength UV rays are more biologically active and are mainly absorbed by the cornea. The longer the wavelength, the more UV rays can penetrate the cornea to reach the lens and retina. Generally, the cornea absorbs UV rays below 300nm, while the lens absorbs UV rays below 400nm. Due to differences in lens coloration, children and adults absorb UV differently; light above 300nm can pass through a child's lens (peak at 380nm), while light above 400nm can pass through an adult's lens (peak at 575nm). This makes children and adolescents more vulnerable to UV damage. Higher light intensity poses a greater risk to eye health, reducing contrast sensitivity, visual comfort, and performance, and causing glare, headaches, and temporary vision impairment.

Additionally, during outdoor activities, children and adolescents may face accidental injuries, such as falls or collisions, which could cause eye injuries like corneal abrasions or blunt trauma to the eyeball. To prevent accidental injuries, parents should ensure children wear appropriate protective gear, such as helmets and goggles, during outdoor activities.

Myopia Prevention Alongside Protection from Light Damage

For children and adolescents participating in outdoor activities to control myopia, it is essential to obtain adequate light exposure while avoiding potential harm from excessive light. Wearing high-quality sunglasses or photochromic lenses, such as those provided by Maat Optical, can effectively block UV rays, reduce glare interference with vision, and minimize irritation from environmental factors like wind and dust.

Photochromic sunglasses are particularly beneficial, as they offer adaptable protection under varying light conditions. These lenses darken in bright sunlight, shielding the eyes from harmful UV rays, and become clear in low-light environments, providing a comfortable visual experience indoors or outdoors. This adaptability makes them ideal for children undergoing myopia control treatment with medium- to high-concentration atropine, as they protect the eyes and reduce discomfort caused by intense light. Additionally, for children using low-concentration atropine, photochromic lenses can alleviate visual symptoms.

Photochromic lenses offer a 97% light transmission rate in clear indoor conditions and 15-22% transmission when activated outdoors, allowing light levels between 1,000 lx and 3,000 lx to reach the eyes—sufficient to delay myopia onset while blocking  of UV rays. Compared to transparent myopia-control lenses, myopia-control lenses with photochromic features provide both effective light protection and myopia control, making them an excellent complement to traditional transparent lenses.

There is currently no evidence suggesting that reducing outdoor sunlight intensity impacts the efficacy of myopia control strategies. For children and adolescents undergoing transparent myopia-control treatment combined with low-concentration atropine, or those who experience photophobia due to higher atropine concentrations, spend significant time outdoors, or engage in outdoor activities in high light-intensity environments, using photochromic myopia-control lenses from Maat Optical is highly recommended for enhanced protection and comfort.