Not long ago, some netizens claimed on social media that after using a phone privacy mask for 2 months, their vision changed from normal to 300 degrees of myopia, and one year later, the degree of myopia climbed to 475 degrees. This matter has attracted widespread attention. At the same time, some businesses claim that privacy films can effectively alleviate visual fatigue. So, what is the anti peeping principle of this membrane? Is it eye protection or eye injury? The reporter interviewed relevant experts to investigate for the public. Grating "locks" the line of sight. With the increasing awareness of personal information protection, a thin layer of privacy film has become a "standard" for many mobile phone users. Its main function is to limit the viewing angle, making the screen content only visible within a certain range on the front. Hu Ke, Deputy Director of Ophthalmology at the First Affiliated Hospital of Chongqing Medical University, introduced in an interview with reporters that the anti peeping principle of the anti peeping film is similar to the shading principle of the blinds. The blades of the blinds are arranged in a fixed angle parallel to each other, and only when the line of sight is aligned with the parallel direction of the blades can the view outside the window be seen. Once deviating from this angle, the line of sight will be obstructed by the blades. The same applies to privacy films. It contains a large number of parallel arranged tiny gratings inside, which are like the blades of a louver and can control the direction of light propagation. When the user looks at the screen within the visible range of the front of the phone, their line of sight is parallel to the grating direction and will not be obstructed, making the screen content visible. ”Hu Ke said that this "frontal visual range" is usually the area where both eyes are facing the screen and the head rotates left and right by no more than 15 degrees. Beyond this range, the light transmittance will significantly decrease, the screen will become dim, and the displayed content will be blurry. Privacy protection film is used to achieve personal privacy protection. The promotion of eye protection has no basis. When searching for "anti peeping film" on various e-commerce platforms, reporters found that the prices of related products range from a few yuan to tens of yuan. Some businesses claim that privacy films not only protect privacy, but also have eye protection functions, which can effectively block blue light. However, in the review section of a certain anti peeping film product with monthly sales exceeding 100000, some buyers expressed that after applying the anti peeping film for several months, their eyes frequently experience soreness and blurred vision. This has raised doubts among consumers about the eye protection function of privacy films. Hu Ke pointed out that there is currently no scientific basis for the promotion of eye protection films on the market. The main research and development purpose of privacy protection film is to protect privacy. The design intention of its grating structure is not to block blue light or relieve eye pressure. Some low-priced products have not even undergone any professional testing, and the so-called eye protection function is mostly a marketing gimmick. Anti peeping film not only does not protect the eyes, but may also pose a risk of eye injury. Hu Ke explained that after the privacy film is applied to the phone, the grating structure will inevitably block some of the light, resulting in a decrease in screen transparency. To see the screen content clearly, mobile phone users usually increase the screen brightness or shorten the distance between their eyes. The blue light radiation intensity of mobile phone screens increases with brightness, and increasing brightness directly leads to an increase in blue light exposure. Excessive blue light can cause temporary damage to retinal photoreceptor cells and may also disrupt the body's biological clock. Watching the screen up close can exacerbate ciliary muscle fatigue, leading to impaired eye regulation function. Over time, the eye muscles remain in a tense state, leading to an accelerated evaporation rate of tears, which may further cause a series of problems such as increased astigmatism and accelerated progression of myopia. What is even more alarming is that the quality of anti peeping film products on the market varies greatly. Some low-priced privacy films not only lack anti blue light and anti flicker functions, but also have defects such as low light transmittance and ripple shaking. Adding the blue light radiation of the phone screen itself, as well as the bubbles and distortions caused by uneven film application, will further reduce the quality of screen content presentation and exacerbate eye discomfort. Three types of people should use caution, Hu Ke suggests. Those with high myopia, dry eye patients, and children and adolescents should use privacy masks with caution. Anti peeping film can reduce the brightness and contrast of mobile phone screens, increase the burden of retinal imaging, and may deepen myopia. Excessive blue light can further damage the already fragile tear film on the ocular surface of dry eye patients, exacerbating discomfort such as dryness and foreign body sensation. The visual system of children and adolescents is not yet fully developed, and prolonged exposure to screens with poor transparency may interfere with normal visual development and pose a risk of myopia. If it is indeed necessary to use privacy film, it is recommended that consumers purchase legitimate products with high light transmittance. ”Hu Ke said that consumers should maintain moderate screen brightness when using privacy films and avoid using electronic products in environments that are too dark or too bright. In addition, when applying the film, it should be applied as smoothly as possible to avoid problems such as bubbles and distortion. Of course, there is no need to blame the decline in vision entirely on the anti peeping film. Poor eye habits are the core cause of visual impairment. ”Hu Ke further said that when using mobile phones in daily life, it is necessary to shorten the continuous use time and follow the "20-20-20" principle, which means that every 20 minutes of use, one should look at objects 20 feet (about 6 meters) away for 20 seconds; Control the distance between the eyes to at least 30 centimeters. Dry eye patients can place the screen under their eyes to reduce the evaporation of tears caused by looking up or down at the screen. Once symptoms such as blurred or double vision, frequent dry and sore eyes, significant short-term vision loss, or accompanied by headaches and dizziness occur, it is recommended to go to a regular hospital for examination as soon as possible. ”Hu Ke added. (New Society)