The intense light and radiation from arc welding equipment pose an immediate threat to unprotected eyes. While a brief flash can cause severe, temporary pain, the risk of permanent blindness is low for individuals who consistently use the correct safety equipment. The difference lies between an acute, temporary injury to the eye’s surface and cumulative, long-term damage to internal structures.
Understanding Acute Injury: Welder’s Flash (Photokeratitis)
The most common acute injury from welding is photokeratitis, known as welder’s flash or arc eye. This condition is a painful sunburn on the cornea, the clear outer layer of the eye, caused by intense ultraviolet (UV) radiation from the arc. Damage to the corneal epithelium can occur within seconds of unprotected exposure.
Symptoms are delayed, typically appearing 3 to 12 hours after exposure. These include a severe, gritty feeling, intense pain, light sensitivity, and excessive tearing. Fortunately, photokeratitis is nearly always temporary and does not cause permanent vision loss because the corneal epithelium is a fast-healing tissue. Most cases resolve completely within 24 to 72 hours, though medical evaluation is often necessary.
The Timeline for Permanent Vision Loss
Permanent vision impairment or blindness is not caused by a single accidental flash, but rather from the cumulative effects of insufficient protection over an extended career. Years of chronic, low-level exposure to the arc’s radiation, often leaking through inadequate gear, leads to the slow development of serious conditions affecting internal structures.
The primary long-term concern is the formation of cataracts, which is the clouding of the eye’s lens. Chronic exposure causes the lens to absorb UV-A and infrared (IR) radiation, accelerating the development of opacities and gradually degrading vision. Another element is chronic retinal injury, known as maculopathy, caused by persistent exposure to visible and near-infrared light reaching the back of the eye. This damage to the macula, responsible for central vision, can progressively worsen over decades, leading to lasting vision reduction.
The Role of UV Radiation in Eye Damage
The danger in a welding arc stems from its broad spectrum of intense electromagnetic radiation, including ultraviolet (UV), visible, and infrared (IR) light. The most damaging component is UV radiation, specifically UV-C and UV-B, which are almost entirely absorbed by the cornea. This absorption is the mechanism that causes the acute corneal burn known as welder’s flash.
UV-A radiation, which has a longer wavelength, bypasses the cornea and is primarily absorbed by the lens, contributing to cataract formation. The bright visible light and IR radiation pose another threat. While IR light is largely absorbed by the lens, intense visible light can pass through to the retina, causing thermal or photochemical damage that may lead to maculopathy.
Essential Protective Measures
Mitigating the risks of both acute and chronic eye injury requires the consistent use of specialized protective equipment. A proper welding helmet, whether passive or auto-darkening, must be worn to shield the eyes from intense radiation. The helmet’s filter lens is rated by a shade number, which indicates its ability to block light and radiation.
For common arc welding processes like Shielded Metal Arc Welding (SMAW) or Gas Metal Arc Welding (GMAW), the required filter shade typically ranges between Shade 10 and Shade 14, depending on the amperage used. A higher shade number signifies a darker filter and greater protection. Standard sunglasses are wholly inadequate for welding, lacking the necessary optical density to block the extreme UV and IR output. Full protection also requires side shields and appropriate clothing, as reflected radiation can damage the eyes and surrounding facial skin.