The public has become increasingly aware of the high-energy visible light emitted by digital screens and modern lighting, leading to a common question about eye protection. Many consumers wonder if the regular prescription glasses they already own offer any defense against this blue light, especially given the hours spent daily interacting with smartphones, computers, and tablets. Determining the level of protection requires understanding the different properties of light and the composition of the lens materials themselves.
Understanding Blue Light and Its Impact
Blue light is part of the visible light spectrum, characterized by shorter wavelengths and higher energy compared to colors like red or green. The highest energy portion, often called high-energy visible (HEV) light, is generally found in the range of 400 to 500 nanometers (nm). A particularly concerning band is the blue-violet spectrum (415 nm to 455 nm), which is believed to be the most potentially hazardous to ocular tissue.
Exposure to this light is associated with two main concerns. The first is digital eye strain, which includes symptoms such as eye fatigue, dryness, and discomfort after prolonged screen use. The second is the disruption of the body’s natural sleep-wake cycle, known as the circadian rhythm. Blue light exposure, especially in the evening, can suppress the production of the sleep-regulating hormone melatonin, making it harder to fall asleep.
Standard Untreated Lenses: The Direct Answer
Standard, untreated corrective lenses generally block very little of the blue light spectrum. The most common lens materials, such as CR-39 plastic and traditional glass, are largely transparent to these high-energy visible wavelengths. These base materials are designed to provide clear vision by transmitting nearly all visible light, including blue light ranging from 400 nm to 500 nm.
It is important to distinguish between blue light and ultraviolet (UV) light. Modern lens materials, including CR-39 plastic and polycarbonate, typically incorporate inherent UV protection, blocking nearly 100% of UVA and UVB rays. However, this UV-blocking capability does not automatically extend to the blue light spectrum. Since UV light ends around 400 nm and the blue light spectrum begins there, the potentially harmful blue-violet light (400-455 nm) is not covered by standard UV protection.
A standard, untreated lens may block minimal blue light wavelengths closest to the UV cutoff, but this amount is insufficient to provide a protective benefit. Studies show that untreated lenses transmit a high percentage of light in the 400–455 nm range. Therefore, a person wearing normal glasses without special filtering technology receives almost the full amount of blue light emitted by digital devices. A specific filtering application must be added to the lens to gain a significant reduction in blue light exposure.
How Specialized Coatings and Materials Filter Blue Light
Eyewear designed to block blue light uses two primary technological approaches. The first involves applying a specialized anti-reflective (AR) coating to the lens surface. This coating is engineered to reflect a portion of the blue light away from the eye, often resulting in a faint blue or purple reflection visible on the lens.
The second approach is to embed filtering pigments directly into the lens material during manufacturing, creating an absorptive lens. These lenses work by absorbing the blue wavelengths as the light passes through the substrate. Lenses with a high degree of blue light absorption often display a noticeable yellow or amber tint, particularly those designed to block 100% of blue light for evening use.
The most effective clear blue light lenses target the most harmful band (400 nm to 455 nm) by incorporating a light yellow hue that is often unnoticeable to the wearer. Consumers should look for lenses that specify the percentage of blue light they filter and the exact nanometer range they target.
Clear blue light lenses typically filter 20% to 40% of the high-energy blue-violet light associated with eye strain. More advanced filters, which may have a slight yellow tint, can filter up to 50% or more across the entire blue light spectrum, including light that affects the circadian rhythm.