- LASER EYE SAFETYBACK TO THE BASICS

Guest Contributor: Dr. Bryan Roof, DO

The Laser: something that nearly everyone in the developed world interacts with daily, yet it has almost lost the respect it deserves. Modern life would not be what it is without this fancy lightbulb.

Initially proposed by Albert Einstein, and first built in 1960 by Theodore Maiman, lasers are different from any other light source due to the coherence of light they emit. This means that laser light is, in essence, very pure in its frequency and waveform. The purity of the light allows for very precise and tight focusing of a laser, which makes it very useful in cutting and engraving. It also allows for using very specific wavelengths of light or very short pulses of light, which optometrists and ophthalmologists take advantage of in eye care for various laser surgeries. Lasers are found in a huge variety of everyday products, such as barcode scanners, disc drives, welding phone lines, skin treatments, and measuring range and speed. Since the very first laser was fired, its potential to cause harm has been well recognized, particularly harm to the eyes. This has resulted in the following safety rating scale we use today, ranging from Class 1 to Class 4.

direct exposure, but scattered exposure is not harmful, 5-499 mW

Class 4 – scattered light from lasers in usage can cause eye damage upon exposure, >500mW

The current rating system is focused on the potential for damage to the eye. The eye is particularly susceptible to laser damage for a several reasons. Obviously being an optical system, the eye is designed to permit light to enter and then focus that light on photoreceptors. Damage to the eye generally occurs to either the photoreceptors of the retina, the lens that focuses light inside the eye, or to the cornea which is the front window of the eye.

Photoreceptors, also known as rods and cones, are

Class 1 – safe during normal usage

Class 1M – safe during normal usage unless magnified with a telescope or microscope

Class 2 – generally safe during normal usage; the eye will be able to blink to protect itself prior to permanent harm

Class 2M – generally safe during normal usage unless magnified

Class 3R – small risk of eye damage during normal use even with the blink reflex, up to 5mW

Class 3B – can cause immediate eye damage upon the light detectors that convert light into an electrical signal that then goes to the brain and processes into what we experience as vision. They are very delicate and active cells, buried deep inside the retina. At first glance, the retina almost appears inside out, as the photoreceptors are not on the surface of the retina but are the very innermost layer. They are very susceptible to thermal damage, which makes them more susceptible to lasers in the visible and near-infrared wavelengths ranging from around 400nm up to 1400nm. The Glow-

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