With the continued introduction of laser devices with unique delivery systems and wavelengths, the issue of eye safety is becoming increasingly complicated. Consistent and competent eye safety procedures for operator, patient, observer and assistant are crucial to a safe and successful laser practice. Despite our increased knowledge of lasers and laser safety, eye injuries in the workplace are still a common problem, with many injuries going undetected well after the incident.
Practitioners must be especially cautious, though, as the longer wavelengths are invisible to the human eye, and longer exposures are innately more likely to occur due to the "invisible" nature of these wavelengths.
Ocular exposure to light or laser can occur directly or via reflection of the beam. Damage will depend on the wavelength of the light, the irradiance and the length of exposure to the eye. When light enters the eye it first travels through the cornea, then is focused by the lens, and if transmissible, through the vitreous humor to the retina.
Those wavelengths that can be transmitted through all parts of the eye and focused onto the retina are able to cause retinal damage. These include those wavelengths between 400 nm and 1,400 nm, the so-called "retinal hazard region." Be especially aware of those wavelengths between 760 nm and 1,400 nm, as these are "invisible" to the human eye, but can still cause serious retinal damage.
Retinal injury results in scotoma (blind spots) or even blindness. Light within the ultraviolet spectrum (290 nm to 400 nm) or far infrared (1,400 nm to 10,600 nm) is not able to pass through the eye, and typically causes damage to the cornea or lens. Q-switched lasers can pose a serious hazard, especially the 1,064 nm (near infrared) because of its "invisible" nature. This beam can penetrate to the retina with little or no signs or symptoms, resulting many times in catastrophic injury to the retina.
Intense pulsed light (IPL) devices pose an interesting problem when deciding on laser safety eyewear (LSE). IPLs emit light in a range of wavelengths ranging from 400 nm to 1,200 nm, depending on the device.
LSE able to block light of this entire range of wavelengths would result in little visibility (low visible light transmittance [VLT]). New "shuttered" lenses have been introduced that will literally blink/close at each pulse of light. Operators must become accustomed to these lenses, as they are heavy and uncomfortable to use.
Hopefully, newer LSE for IPLs will be introduced in the near future. Recommended LSE for IPLs at the present time is either "shuttered" lenses, or protection against the mid wavelengths, and blinking by the operator at each pulse.