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How Does Laser Damage Your Eyes?

February 1, 2021

Laser, is a kind of light due to the excitation of the light with good directivity, high brightness, good monochromatism and good coherence, which did not exist in nature. Laser is another major invention of human beings since the 20th century, following nuclear energy, computer and semiconductor. It is known as "the fastest knife", "the most accurate ruler" and "the brightest light". The light emitted by excitation of atoms is named "laser".

 

The mechanism of laser damage to human eyes is very complex. There are mainly three kinds of damage effects:

1. Thermal effect: the laser is converted into heat energy after being absorbed by the eye tissue, and the local temperature rises, causing protein destruction and cell damage.

2. Shock wave effect: the retina receives strong light irradiation in a short time. Due to the photon impact and rapid thermal expansion of the illuminated tissue, shock wave is generated, which spreads to the surrounding tissue and causes injury.

3. Photochemical effect: laser irradiation on eye tissue causes the vibration of atoms and molecules in the tissue, causing electromagnetic effect and ionization to damage it.

Laser damage to the eyes often have the above several effects at the same time.

 

 

The human eye is the most vulnerable organ by laser damage, this is because retina tissue can effectively absorb multiple wavelength lasers. And eyeball itself has good focusing system, light energy density produced by laser from the pupil to retina increased, so the threshold of eye tissue damage by laser is lower than that of other organs. And the biological effects of laser can have a cumulative effect, a single irradiation does not cause damage, but many times of irradiation may cause damage. The victims of repeated laser irradiation often do not feel obvious harm in eyes, they only feel a gradual decline in vision.

 

The area of eye tissue damaged by laser is related to the wavelength of laser.

UV light below 300nm cannot pass through the refractive medium of eye, and is almost completely absorbed by the cornea, which can cause electro-optic ophthalmitis.

UV light of 300nm ~ 400nm is mainly absorbed by the crystal, which can cause radiation cataract.

Visible light of 400nm ~ 800nm and near-infrared light of 800nm~900nm can reach the retina through the refractive medium and be absorbed by the pigment cells, causing retinal burns and even bleeding.

Infrared light above 950nm can be absorbed by the refractive medium of the eye and damage the superficial eye tissues like cornea and crystal, in the form of thermal radiation.

 

Laser damage to eye tissue is also related to some other factors. For example, the greater the laser energy, the greater the damage to the eyes. The smaller the angle at which the laser hits the eye, the greater the damage, because the smaller the angle of incidence, the smaller the image on the retina, the more concentrated the energy density. If eyes stare right up at the laser beam, the laser is focused in the fovea of the retina, which has a greater impact on vision. Retinal damage is more likely to occur at night than during the day because the pupil dilates at night and the retina receives more laser energy as the laser radiates the same energy density.

According to the standards set by the nation, lasers with a duration of more than 0.1 second cannot have more than 10-4 watts of power, which is the safe threshold for lasers.

The laser lamp that we come into contact with in daily life will not exceed this standard generally, but if with frequent contact with laser and paying no attention to protection, laser also could cause chronic injury. Once eye damage has occurred, it is too late to repair it, because the death of photoreceptor and pigment cells in the retina caused by lasers is irreversible. Therefore, in our daily life, we must pay attention to the protection of our eyes, try to avoid laser irradiation, do not look directly at the laser because of curiosity or fun.

The safety premise of using laser cleaning machine, marking machine or welding machine is that users do not look directly at the laser. And be sure to wear professional goggles when using the machine. Our machine will give you specific goggles according to the laser wavelength, please rest assured to use it.

 

(Source: Chengdu SID Security)