Is laser dangerous? What happens if the laser beam hits the eye? Or a few words about safety during laser procedures in cosmetology

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What happens if the laser beam hits the eye? Or a few words about safety during laser procedures in cosmetology

This is 50 years ago, the laser was used only to remove neoplasms, and then - on the face and body. Since the advent of devices with finer settings, anti-aging and tattoo removal procedures have begun to affect the eyebrows, outer corners of the eye, and the ciliary edges of the eyelid. But it's not far from the eye! Is it dangerous or not? What happens if the laser does hit the eye? How to eliminate risks for the patient and for the doctor?

Lasers are different

Medical laser systems have 4 hazard classes:

1. Class 1 considered incapable of generating damaging levels of radiation during operation. It is safe under all conditions of normal use with the naked eye or magnifying optics. These systems are exempt from any controls or other types of surveillance. An example is the lasers used in diagnostic laboratories. Class 1M is considered incapable of producing dangerous conditions impact during normal operation, if the beam is not viewed with magnifying optics.
2. Class 2– low power laser systems; they emit light in the visible part of the spectrum (400-700 nm) and are considered safe because defense mechanisms (our blinking reflex) provide protection. An example is the helium-neon laser (laser pointers).
   Class 2M - emits light in the visible part of the spectrum. Eye protection is normally provided by the involuntary closing of the eyes when looking at them. However, these systems are potentially dangerous when viewed with certain optical devices.
3. Medium power laser systems class 3. They can be dangerous when viewed directly or looking at the specular reflection of the beam. They are not sources of diffuse reflection and are not fire hazardous. An example of a class 3 laser is the Nd:YAG laser used in ophthalmology.
   There are 2 subclasses: 3R and 3B. Class 3R. Can be dangerous under some direct and specular conditions if the eye is properly focused and stable, with little chance of actual damage. Class 3B. Can be dangerous in direct and specular reflection conditions.
4. Class 4. These are high power systems. They are the most dangerous, they can be sources of diffuse reflection, and are fire hazardous. They can also generate dangerous plasma radiation. These are cosmetic lasers: carbon dioxide, neodymium, argon, alexandrite, pulsed dye laser (PDL).

The principle of the laser

The wavelengths of laser radiation fall into the ultraviolet, visible and infrared ranges of the electromagnetic spectrum.

Almost all cosmetic lasers work on the principle of selective photothermolysis. This means that their laser energy is absorbed by a specific chromophore:

• melanin - for diode, alexandrite and ruby ​​laser and dye laser (PDL);
• hemoglobin for neodymium in yttrium aluminum garnet and PDL;
• water - for erbium and carbon dioxide lasers, while maintaining the surrounding tissue.

For the laser to have the desired effect, three basic requirements must be met:

1. Sufficient wavelength for a certain penetration depth.
2. Exposure duration (laser pulse width and duration) less than or equal to the thermal relaxation (TRT) of the target.
3. Sufficient energy per unit area (fluence) to cause irreversible damage to the target chromophore.

The power, spot size and duration of the laser are also important. So, with a larger spot size, there is less scattering, but deeper tissue penetration.

Although lasers target specific chromophores, the ambient scatter and resulting thermal effect can cause side effects. Thermal damage occurs when sufficient energy is absorbed by the appropriate chromophore at a rate faster than the resulting heat can be dissipated. While the main tissue chromophores are targeted, other eye structures that are also rich in these chromophores are susceptible to inadvertent damage. They may be the retina, rich in hemoglobin and melanin, choroid, rich in melanin, cornea and lens, containing a lot of fluid.

Features of the eyelid and eye

When carrying out laser procedures in the area around the eye, you need to remember the following:

• The skin of the eyelids is very thin.
• The eye contains several targets for different laser beams. These are melanin in the epithelium of the retina, the pigment of the iris, as well as water, which makes up most of the eyeball.
• The most vulnerable part of the eye is the retina: a laser beam of 400-1400 nm in length (and especially 700-1400 nm) is focused directly on it using the bulges of the lens and cornea. As a result, the retina receives 105 times more radiation than the cornea.
• There is such a thing as the Bell phenomenon: when the eye is closed, eyeball naturally rolls up. Thus, the pigmented iris can enter the laser penetration range and absorb the radiation.
• Pain receptors are located very densely on the cornea. That is, even its slight thermal damage leads to severe pain.

Light-eyed patients are especially prone to laser injury if the treatment is carried out with a laser whose target is melanin. In them, all the radiation hits the retina immediately, without decreasing when passing through the epithelium of the iris.

How the laser damages the structures of the eye

Laser injury to the eye and the possible degree of damage is different and depends on the type of laser. Thus, devices based on potassium titanyl phosphate (KTP) or dyes (PDL) have a short length. They are mainly absorbed by the cornea and lead to photocoagulation, i.e. photothermal effect.. In this case, enough heat is generated in the eye tissue to denature the proteins. The temperature of the retina can increase from 40 to 60°C.

Lasers emitting a long wave - infrared, diode, Nd: YAG. They pass through the cornea to reach the lens and retina. Their effect is photomechanical, less often - the phenomenon of photocoagulation. The photomechanical effect implies that an explosive acoustic shock is generated in the tissues, which can lead to the appearance of fragments and even perforation of individual structures.

For example, clinically, the 1064 nm Nd:YAG laser, which causes most laser eye injuries, is capable of causing retinal hemorrhage, in vitreous body, as well as scarring, the formation of preretinal adhesions and retinopathy, when the radiation is absorbed by the retinal pigment epithelium, saturated with melanin. The Nd:YAG laser can cause significant damage to the eye and surrounding skin compared to shorter wavelength lasers because it can penetrate deeper layers of the skin.

The danger of long wavelength lasers (for example, 755-795 nm alexandrite and Nd: YAG laser with a wavelength of 1064 nm) is that their beam is not visible to the eye. This distinguishes them from shorter wavelength (eg KTP) lasers.

Erbium: YAG laser at 2940 nm is another ablative laser that can also be used fractionally. It absorbs more efficiently into water and collagen and causes less thermal damage than CO2 laser. Complications of these lasers include erythema, hyper- and hypopigmentation of the iris, skin infections, and corneal trauma.

I came across these statements online:
You can move the laser from the balcony and burn someone's retina. You, your parents, your children. Do you understand? It is freely available, without restrictions.
The scorched retina is not restored. Idiots who sell such things to such idiots should be punished. If I see an idiot on the street with a similar toy, I will take it away from the youngster and give a couple of slaps in the face. Who is older - I will punish much more seriously, up to stab-cut and gunshot. Bought - burn the retina yourself. You endanger others - get it.

Let's not discuss here mental state the author of such statements, but you can talk about the safety of laser pointers.

To begin with, it is worth noting that a laser is, of course, a device that poses a threat to vision, and sometimes to life. AT general case it should not be directed where a person's face may be. And you can play with cats only using the least powerful models. For lasers more powerful than 5 mW, it is very desirable to have goggles, and if the power is measured in hundreds of milliwatts, it is not only dangerous, but also simply unpleasant to work without them.

BUT, the danger of modern pointers in the mass consciousness is greatly exaggerated. I have already touched on this topic in this article. Here I will cite separately the question of the danger of pointers, compressed from the point of view of artistry and expanded from the point of view of information.

Firstly, it is worth noting right away that a laser pointer cannot provide “bang - and you are blind”. Even if you specifically direct the most powerful model directly into your eye. As a rule, this leads to the fact that another blind spot appears on the retina (in addition to what everyone already has from birth). Within a few months after the injury, the brain updates the "map of dead pixels" and the spot ceases to cause discomfort. But the image of objects that fell into the region of the spot, of course, is not perceived by the eye. Usually you need to make a special effort to notice this (we search the Internet for "blind spot detection"). One of my acquaintances, who was engaged in the alignment of lasers, has several such spots, but in life they do not interfere with him in any way. Of course, this is not a reason to "get on the rampage", especially since in some cases a much more serious loss of vision is possible. But this is a reason to stop being afraid that at any second someone can deprive you of your sight by shining a pointer from the balcony.

Secondly, it would be a serious mistake to assume that the light from the laser propagates strictly in parallel. It has a certain divergence. For most pointers, it is in the range of 1-2 mrad, and for the worst - 5 mrad or even more. Only the light that enters the pupil of the eye, whose area even on a dark night does not exceed 50 mm 2, is dangerous for vision. The farther the eye is from the pointer, the less power it can get into the eye. One well-known manufacturer of heavy-duty pointers lists in their characteristics, among other things, the range to which they pose a danger. For 1000 mW (exactly one thousand) of a pointer with a divergence of 1.5 mrad, this is 150 m. Further, it does not pose a serious threat. But most of the pointers of such huge power sold now have at least twice the divergence, which proportionally reduces the dangerous distance. So a beam that "arrived" hundreds of meters away cannot injure anyone. The same applies to an accidental hit of a reflected beam in the eye: in most cases, only a specular reflection from a flat or slightly concave surface is dangerous. Reflection from a convex or matte surface can spoil vision only during long-term observation, because. only a small part of the emitted power reaches the eye.

Finally, power records have nothing to do with the power of those pointers that are sold in underground passages. Most likely, you will not find even 500 mW models there. From the strength of 200-300 mW. But these numbers are too high. Experience has shown that Chinese green pointers usually have 1.5-3.0 times less power than advertised. Sometimes they deceive even 10 times ... High-quality powerful pointers, although they are getting cheaper, are not at all as fast as they scare us. If five years ago a high-quality 300 mW model cost $1000, now the price has dropped to $300. Even if in another 5 years the price drops to $100, this is still clearly not the price at which schoolchildren will buy it en masse.

Lasers and radiation from them have been used by mankind for quite a long time. In addition to the medical environment, such devices are widely used in technical industries. They were adopted by specialists from the field of decorating and creating special effects. Now, not a single large-scale show is complete without a stage with laser beams.

A little later, such radiation ceased to take only industrial forms and began to occur in everyday life. But not everyone knows how the effect of laser radiation on the human body is reflected with regular and periodic exposure.

What is laser radiation?

Laser radiation is born according to the principle of creating light. In both cases, atoms are used. But in the situation with lasers, there are other physical processes, and the effect can be traced electromagnetic field external type. Because of this, scientists call the radiation from lasers forced or stimulated.

In the terminology of physics, laser radiation is called electromagnetic waves that propagate almost parallel to each other. Because of this, the laser beam has a sharp focus. In addition, such a beam has a small scattering angle, together with a huge intensity of influence on the surface that is irradiated.

The main difference between a laser and a standard incandescent lamp is the spectral range. The lamp is considered a man-made light source that emits electromagnetic waves. The lighting spectrum of a classic lamp is almost 360 degrees.

The impact of laser irradiation on all living things

Contrary to stereotypes, the effect of laser radiation on the human body does not always mean something negative. Due to the widespread use of quantum generators in various areas of life, scientists decided to use the capabilities of a narrow beam in medicine.

In the course of numerous studies, it became clear that laser irradiation has several characteristic properties:

• Damage from a laser can be produced not only in the process of direct exposure to the body from the apparatus. Even scattered radiation or reflected rays can cause damage.
• There is a direct relationship between the degree of damage and the main parameters of the electromagnetic wave. The location of the irradiated tissue also affects the severity of the lesion.
• The negative effect of energy absorption by tissues can be expressed in thermal or light exposure.

But the sequence in case of laser damage always provides for an identical biological principle:

• an increase in temperature, which is accompanied by a burn;
• boiling of interstitial and cellular fluids;
• the formation of steam that creates significant pressure;
• explosion and shock wave destroying all tissues nearby.

Often, an incorrectly used laser emitter poses, first of all, a threat to skin. If the influence was especially strong, then the skin will look edematous, with traces of numerous hemorrhages. Also on the body there will be large areas of dead cells.

Touches such exposure and internal tissues. But with large internal lesions the scattered effect of the rays is not as strong as the direct or reflected specular effect. Such damage will guarantee pathological changes in the functioning of various body systems.

The skin that suffers the most is the defense internal organs each person. Because of this, he takes most of negative impact to myself. Depending on the different degrees skin lesions will show redness or necrosis.

The researchers concluded that dark-skinned people are less susceptible to deep-seated lesions due to laser irradiation.

Schematically, all burns can be divided into four degrees, regardless of pigmentation:

• I degree. It implies standard burns of the epidermis.
• II degree. Includes burns of the dermis, which is expressed in the formation of characteristic blisters of the surface layer of the skin.
• III degree. Based on deep burns of the dermis.
• IV degree. The most dangerous degree, which is characterized by the destruction of the entire thickness of the skin. The lesion covers the subcutaneous tissue, as well as the layers adjacent to it.

Laser eye lesions

In second place in the unspoken rating of the possible negative effects of the laser on the human body are lesions of the organs of vision. Short laser pulses can disable in a short period of time:

• retina,
• cornea
• iris,
• lens.

There are several reasons for such an impact. The main ones are:

• Inability to respond in time. Due to the fact that the pulse duration is no more than 0.1 seconds, a person does not have time to blink. Because of this, the eye remains unprotected.
• Slight vulnerability. According to their characteristics, the lens and cornea are considered vulnerable organs in themselves.
• Optical eye system. Due to the focusing of laser radiation on the fundus, the irradiation point, when it hits a retinal vessel, can clog it. Since there are no pain receptors there, damage cannot be detected instantly. Only after the scorched area becomes larger, the person notices the absence of part of the image.

To quickly navigate with a potential lesion, experts advise listening to the following symptoms:

• eyelid spasms,
• eyelid edema,
• pain sensations,
• retinal hemorrhage,
• turbidity.

The danger is added by the fact that laser-damaged retinal cells lose the ability to recover. Since the intensity of radiation affecting the organs of vision is lower than the identical threshold for the skin, doctors are calling for caution.

Beware of infrared lasers different type, as well as devices that generate radiation with a power of more than 5 mW. The rule applies to equipment that produces rays of the visible spectrum.

Relationship between laser wave and its scope

Each of the areas of application of laser radiation is guided by a strictly defined wavelength indicator.

This indicator directly depends on nature. Rather, from the electronic structure of the working fluid. This means that the medium where the generation of its radiation takes place is responsible for the wavelength.

There are different types solid-state and gas lasers. The beams involved must be one of the three most common types:

• visible,
• UV,
• infrared.

In this case, the operating range of irradiation can vary from 180 nm to 30 mnm.

Features of the influence of the laser on human body based on wavelength. So, for example, a person responds faster to a green laser than to a red one. The latter is not safe for all living things. The reason lies in the fact that our vision perceives green almost 30 times more than red.

How to protect yourself from the laser?

In most cases, protection from laser radiation is needed by those people whose work is closely related to its constant use. If an enterprise has any type of quantum generator on its balance sheet, then its managers must instruct their employees.

The experts have developed a separate set of rules of conduct and safety that will protect the employee from possible consequences radiation. The main rule is the availability of personal protective equipment. Moreover, such funds can differ dramatically depending on the predicted degree of danger.

Total in international classification divided into four hazard classes. The appropriate marking must be provided by the manufacturer. Only the first class is considered relatively safe even for the organs of vision.

The second class includes direct-type radiation that affects the organs of the eyes. Mirror reflection is also included in the presented category.

Radiation of the third class is much more dangerous. Its direct effect threatens the eyes. Diffuse-type reflected radiation at a distance of 10 cm from the surface is no less dangerous. Skin lesions will occur not only with direct exposure, but also with mirror reflection.

In the fourth grade, both the skin and the eyes suffer from various exposure formats.

Collective protective measures at work include:

• special covers,
• protective screens,
• light guides,
• innovative tracking methods,
• alarm,
• blocking.

Of the relatively primitive, but effective ways allocate a fence of the zone where irradiation is performed. This will protect workers from accidental exposure through negligence.

Also, at especially dangerous enterprises, it is mandatory to use personal protective equipment for employees. They mean a special set of overalls. You can’t do without wearing goggles that provide a protective coating during work.

Laser gadgets and their radiation

Many are unaware of how serious the consequences of the uncontrolled operation of home-made devices with a laser principle can be. This applies to home-made structures like laser ones:

• lamps,
• pointer,
• flashlights.

This is especially true for high school students who seek to conduct a series of experiments without having an idea about the safety rules when designing them.

It is unacceptable to use home-made lasers in rooms where people are present. Also, do not direct the rays at glass, metal buckles and other objects that can give reflections.

Even if the beam is of low intensity, it can lead to tragedy. If you point the laser at the driver's eyes during active movement, he may go blind and lose control.

Under no circumstances should you look into the lens of the laser source. Separately, it should be taken into account that glasses for working with a laser must be designed for the wavelength that the selected devices will generate.

In order to prevent a serious tragedy, doctors are asked to listen to these recommendations and follow them at all times.

The laser is very dangerous. Tissues and organs that are commonly exposed to laser radiation are the eyes and skin. There are three main types of tissue damage caused by laser irradiation. These are thermal effects, photochemical effects, as well as acoustic transient effects (only the eyes are affected).

• Thermal effects can occur at any wavelength and are the result of radiation or light effects on the cooling potential of tissue blood flow.
• In air, photochemical effects occur between 200 and 400 nm and ultraviolet, and between 400 and 470 nm violet wavelengths. Photochemical effects are related to the duration and also the repetition rate of the radiation.
• Acoustic transient effects associated with pulse duration can occur in short pulse durations (up to 1 ms) depending on the specific laser wavelength. The acoustic impact of transient effects is poorly understood, but it can cause retinal damage that is distinct from thermal retinal injury.

Potential harm to the eye

Potential eye damage sites (see Figure 1) are directly related to the laser wavelength. Effect of laser radiation on the eye:

• Wavelengths shorter than 300 nm or more than 1400 nm affect the cornea
• Wavelengths between 300 and 400 nm affect the aqueous humor, iris, lens and vitreous.
• Wavelengths from 400 nm and 1400 nm are aimed at the retina.

NOTE: The damage of the laser to the retina can be very large due to the focal gain (optical gain) from the eyes, which is approximately 105. This means that the radiation from 1 mW/cm2 through the eye will be effectively increased to 100 mW/cm2 when it reaches the retina. .

At thermal burns the cooling function of the vessels of the retina of the eye is disturbed. As a result of the damaging effect of the thermal factor, hemorrhages into the vitreous body may occur as a result of damage to the blood vessels.

Although the retina can recover from minor damage, major injuries yellow spot retinal damage can lead to temporary or permanent loss of visual acuity or complete blindness. Photochemical injury to the cornea ultraviolet irradiation can lead to photokeratoconjunctivitis (often called welder's disease or snow blindness). This is painful conditions may last several days with very debilitating pain. Long-term ultraviolet exposure can lead to the formation of cataracts.

The duration of exposure also affects eye trauma. For example, if a visible wavelength laser (400 to 700 nm) has a beam power of less than 1.0 MW and an exposure time of less than 0.25 seconds (the time it takes a person to close their eyes), there will be no damage to the retina. Class 1, 2A and 2 lasers fall into this category and generally cannot harm the retina. Unfortunately, direct or reflected hits from Class 3A, 3B, or 4 lasers and diffuse reflections from lasers above Class 4 can cause damage before the person can reflexively close their eyes.

For pulsed lasers, pulse duration also affects potential eye damage. Pulses less than 1 ms on impact on the retina can cause acoustic transient effects resulting in significant damage and bleeding in addition to the expected thermal damage. Many pulsed lasers currently have pulse times of less than 1 picosecond.

The ANSI standard defines the maximum allowable power (MWR) of laser exposure to the eye without any consequences (under the influence of specific conditions). If the MDM is exceeded, then the probability of damage to the eyes increases dramatically.

First rule of laser safety: NEVER UNDER ANY CIRCUMSTANCES LOOK WITH YOUR EYES INTO THE LASER BEAM!

If you can prevent the laser beam and its reflections from reaching the eye, you can avoid painful and possibly blinding injuries.
Potential harm to the skin.

Skin injury from lasers primarily falls into two categories: thermal injury (burns) from acute exposure to high-power laser beams and photochemically induced injury from chronic exposure to diffuse ultraviolet laser radiation.

• Thermal injury can result from direct contact with the beam or its specular reflection. These injuries, although painful, are usually not serious and are usually easily prevented with proper control of the laser beam.
• Photochemical damage can occur over time from ultraviolet exposure to direct light, specular reflections, or even diffuse reflection.

Effects may be minor but may cause severe burns, and prolonged exposure may contribute to the formation of skin cancer. Good safety goggles and clothing may be necessary to protect the skin and eyes.

Laser safety

When working with lasers, it is necessary to wear goggles that protect against laser radiation. Are these special glasses really needed? Many novice laser builders and buyers of laser pointers ask themselves this question. Yes, goggles are needed even for a 15mW laser, because without them the eyes get very tired. Glasses cost about 1600 rubles apiece, but I think you understand that your eyes are worth a lot more than you pay for glasses. Do not use sunglasses to protect your eyes!

The same will happen with your eyes...
The degree of protection of glasses from laser radiation is measured in OD. What does OD stand for? OD stands for Optical Density. Optical density shows how many times the glasses attenuate light. One means "10 times". Accordingly, "optical density 3" means attenuation by a factor of 1000, and 6 - by a million. The correct optical density for a visible laser is such that after glasses from a direct hit of the laser, the power corresponding to class II remains (maximum somewhere around 1 mW). For the invisible - the more the better.
Domestic glasses of the brand ZN-22 C3-C22 protect against red and some infrared lasers. They look like welder goggles but have glasses. blue color. You can sometimes buy them in Medtekhnika stores, they cost about 700 rubles. The disadvantage is that they are rubbery, heavy and ugly. If you're lucky, you can buy other domestic laser glasses. But they are rarely on sale.
On our website in the links section you can find many addresses of shops selling laser accessories including safety glasses.