Infrared (IR) light is a form of electromagnetic radiation that falls just outside the visible spectrum, possessing wavelengths longer than those of red light. While we cannot see this energy, we often perceive it as heat, and it is a natural component of sunlight. Whether infrared light can damage the eyes depends entirely on the intensity and duration of the exposure. Under high-intensity conditions, such as those found in industrial environments or from certain powerful artificial sources, IR radiation carries the potential to cause serious and permanent ocular damage.
The Different Types of Infrared Radiation
Scientists classify infrared radiation into three sub-bands based on wavelength, which determines how deeply the energy penetrates the eye’s tissues. Near-Infrared (IR-A) has the shortest wavelengths, ranging from approximately 700 to 1,400 nanometers, and is the most concerning for deep tissue damage. This radiation can pass through the cornea and lens, reaching the sensitive retina at the back of the eye.
The Mid-Infrared (IR-B) band spans from 1,400 to 3,000 nanometers, while Far-Infrared (IR-C) includes all wavelengths longer than 3,000 nanometers. These longer wavelengths are almost entirely absorbed by the anterior structures of the eye, specifically the cornea and the lens. Because water is a powerful absorber of IR-B and IR-C, these bands do not penetrate deeply but instead deposit their energy close to the surface.
How Infrared Light Causes Ocular Damage
The mechanism by which infrared light harms the eye is thermal; the damage results from a buildup of heat. Unlike ultraviolet light, which causes photochemical changes by breaking molecular bonds, IR radiation simply raises the temperature of the tissue it strikes. If the intensity is high enough, this temperature increase can denature proteins and cause thermal burns, leading to irreversible tissue damage.
The effects of Mid- and Far-Infrared (IR-B and IR-C) are concentrated in the anterior segment of the eye, mainly impacting the cornea and the lens. Chronic exposure to these wavelengths can lead to lenticular opacities, historically known as “glassblower’s cataract.” This condition occurs because heat absorbed by the iris and surrounding structures is conducted to the lens, causing the proteins within it to aggregate and cloud. Workers dealing with molten glass or steel were historically susceptible to this specific type of injury.
Near-Infrared (IR-A) is hazardous because it transmits through the clear ocular media to reach the retina. Since the eye’s lens focuses this radiation, the energy is concentrated onto the small area of the retina, which contains the photoreceptor cells. At high intensity, this focused heat can cause photocoagulation, essentially a thermal burn. This acute damage to the retinal pigment epithelium can occur rapidly, resulting in immediate and permanent vision impairment.
Common Sources of Ocular Exposure
While everyday sources like television remote controls or low-power household heaters emit IR light, the levels are generally too low to cause harm under normal use conditions. The danger comes from high-irradiance sources found in industrial, medical, and natural settings. Industrial environments are major sources of high-intensity IR radiation, including glass manufacturing, metal foundries, arc welding, and steel processing.
The intense thermal radiation from these processes is often invisible but can quickly exceed safe exposure limits. High-power lasers used in industrial or medical applications also emit IR-A or IR-C wavelengths that pose a threat to the eyes. Even natural sources like the sun are dangerous, as solar radiation contains a significant percentage of IR energy. Staring directly at the sun, especially without specialized filters, delivers a dose of IR-A that can cause severe retinal burns.
Protecting Eyes From Infrared Exposure
Protection against infrared exposure requires specific, targeted measures that go beyond standard sunglasses or clear safety glasses. In occupational settings, specialized safety eyewear complying with standards like ANSI Z87.1 or EN 171 is required for workers. These glasses feature lenses with specific filters and absorbing coatings designed to block dangerous IR wavelengths.
Infrared protective eyewear is marked with ‘IR’ and a scale number indicating the level of protection, ranging from 1.3 to 10. The shade level must be selected to match the intensity of the IR source. Safety protocols also involve engineering controls, such as shielding hot processes and maintaining safe working distances. Limiting the duration of exposure is a control measure, as thermal damage is cumulative and time-dependent.