Laser, as a high-intensity, monochromatic, coherent light source, has been widely used in the fields of medicine, industry, scientific research and military since its invention. However, the high-energy characteristics of laser also make it a potential source of danger, especially for the sensitive organ of the eye. Laser damage to the eye may cause serious visual damage in a short period of time, or even permanent blindness. Therefore, it is crucial to understand the symptoms of laser eye damage and take effective protective measures.
Symptoms of laser damage to the eye
1. Visual interference
After laser irradiation, patients may experience various forms of visual interference, including but not limited to:
- Flash sensation: a brief bright light or flickering phenomenon in front of the eyes.
- Floaters: seeing small black dots or lines floating in front of the eyes.
- Halo effect: a halo or rainbow-like edge appears around the light source.
- Vision retention: the image will temporarily stay in the field of vision after strong light stimulation.
These symptoms may gradually disappear over time, but they may also persist and affect daily life.
2. Pain and discomfort
Laser-induced eye pain may be a momentary stinging sensation or a persistent burning or pressure sensation. This pain may be accompanied by the following symptoms:
- Dry eyes: Reduced tear production, leading to dry eyes.
- Foreign body sensation: Feeling like there is sand or other foreign objects in the eye.
- Blepharospasm: Involuntary blinking or eyelid twitching.
These discomforts may affect the patient's work and quality of life.
3. Vision changes
Laser exposure may cause short-term fluctuations in vision, including:
- Increased myopia: Temporary or permanent increase in myopia.
- Increased hyperopia: Distant objects become blurry.
- Astigmatism: Light cannot focus properly on the retina, causing distorted vision.
- Diptyopia: One object appears to be two or more.
These vision changes may cause great inconvenience to patients.
4. Eye inflammation
Laser-induced eye inflammation may include:
- Conjunctivitis: Reddening and swelling of the conjunctiva, accompanied by increased secretions.
- Iritis: Inflammation of the iris, causing eye pain, photophobia, and pupil constriction.
- Uveitis: Inflammation of the uvea inside the eye, which may affect vision and cause eye pain.
These inflammations require prompt medical treatment to prevent further complications.
5. Permanent damage
In the most severe cases, laser exposure may cause permanent eye damage, such as:
- Corneal scarring: Permanent scar tissue formed on the surface of the cornea.
- Cataract: Clouding of the lens, affecting vision.
- Retinal detachment: The retina detaches from the fundus, which may cause blindness.
- Optic atrophy: Decreased optic nerve function, leading to vision loss.
These permanent injuries require surgery or other medical treatment, but the possibility of recovery is limited.
How to choose laser protective glasses
1. Introduction to EN207 standard
EN207 is the EU standard for laser protective glasses, which aims to ensure that these glasses provide adequate protection when facing different types and wavelengths of laser radiation. The standard specifies the classification level, labeling requirements and test methods of laser protective glasses in detail. Choosing protective glasses that meet the EN207 standard is the first step to ensure eye safety.
2. Classification level and labeling
The EN207 standard requires that the classification level of laser protective glasses should be marked with the CE mark, and the LB grade specification must be printed on the lens. The LB grade consists of three parts: wavelength range, laser mode name, and scale number. This information helps users choose the right protective glasses. For example, LB/200~300nm means that the glasses are suitable for lasers with wavelengths in the range of 200 to 300 nanometers.
3. Wavelength range and laser mode
The EN207 standard divides laser modes into D (continuous wave), I (pulse length >1us), R (pulse length <1ns), and M (pulse length >1ns and <1us) based on different pulse times. Users need to judge whether laser safety glasses meet the minimum protection level requirements for a given laser based on these parameters. For example, for pulsed lasers, protective glasses suitable for I or R mode should be selected.
4. Optical density and damage value
The EN207 standard not only considers the optical density (OD) of the glasses, but also introduces the concept of damage value. The damage value indicates the maximum power or energy density that the glasses can withstand, thereby more comprehensively evaluating the protective ability of the glasses. This improvement solves the problem that may arise from relying solely on optical density, because lasers of different wavelengths cause different degrees of damage to the eyes. For example, a high-power, low-energy-density laser may not cause immediate harm, but prolonged exposure may still cause chronic damage.
5. Visible light transmittance (VLT)
Visible light transmittance refers to the ability of protective glasses to allow visible light to pass through. The higher the VLT value, the clearer the wearer can see. However, a high VLT value may reduce the protective effect of the glasses against certain wavelengths of lasers. Therefore, when choosing protective glasses, it is necessary to find a balance between safety and visibility. Generally speaking, the VLT value should be between 10% and 30% to ensure both effective protection and good visual clarity.
6. Comfort and fit
In addition to technical parameters, the comfort and fit of protective glasses are also important considerations. Wearing inappropriate glasses for a long time may cause headaches, facial indentations and other problems. Therefore, it is recommended to try on multiple glasses before purchasing to find a style that meets safety standards and is comfortable. In addition, factors such as the weight, material and design of the glasses should also be considered to ensure that they are safe and comfortable in daily use.
Conclusion
Laser eye injury is a serious occupational health problem that not only affects an individual's visual health, but may also have a profound impact on their career and social function. By understanding the specific ways in which lasers harm the eyes and their symptoms, we can better understand the importance of protection. Choose the right laser protective glasses.