[Medical Q&A] It’s scary, can a laser pen have such great “lethal power”?

Author: Song Run, Children's Hospital Affiliated to Suzhou University

Reviewer: Feng Kehong, Chief Physician, Children's Hospital Affiliated to Soochow University

Laser pointers are commonly known as "laser pens" and are usually used to project light spots or point to objects during work reports, teaching, and tour guides. Monochromatic lasers of different wavelengths are absorbed by different tissues due to photothermal or photochemical effects, which can cause carbonization, gasification, and denaturation of tissues, resulting in local burns and coagulative injuries.

Laser pens can be accurate to micron level and are often used in laser cutting, welding, drawing, etc. They can also be used for navigation, long-distance indication, search and rescue, etc. But at the same time, the "lethality" of laser pens is also quite extraordinary. If used improperly, direct exposure to the eyes can cause damage to the eyes and even lead to blindness!

So, how does a laser pen affect vision? Laser pens can easily cause damage to the macular area.

Functional damage, in severe cases may cause blindness. The macula is located in the center of the retina and is the most sensitive area for vision. The macula has dense retinal pigments and is easily absorbed by the laser energy, thus being damaged by the laser thermal radiation. Any damage involving the macula will cause a significant decrease in central vision, dark and distorted vision, etc.

The harm of laser pens to the eyes is mainly caused by its thermal effect. The laser passes through the cornea to reach the retina at the fundus. The outermost pigment epithelium of the retina contains more melanin, which has a significant absorption effect on the laser. If a certain amount of heat is generated, it will burn the retina and cause vision loss. Many laser pens sold on the market belong to Class 3B, with a power of more than 5mW. If the laser is directly shot into the eye, it will be absorbed by the pigment epithelium of the fovea. Therefore, some high-power laser pens can even cause macular holes.