How Safe are Lasers?

Q:  Recently I read in the Milwaukee Journal-Sentinel a rather frightening article about the irresponsible uses of laser beams. Several persons who suffered permanent eye damage from a laser beam directly to the eye were mentioned.

Many of us have had laser surgery performed on our eyes. While this has been done by a responsible, trustworthy physician who has training in doing laser surgery, I (and probably others as well) still wonder whether even controlled laser beams might damage the eye.

My own experience with laser surgery happened about 15 years ago, when much less was known on this subject.

A:  Lasers are concentrated beams of light which can very precisely cut, seal, heat, and even vaporize tissue. Much like a knife, they can cause harm when used indiscriminately, but in the best hands, lasers have many revolutionary medical uses. I spoke with Dennis Han, MD, Professor of Ophthalmology and Tom Connor, MD, Associate Professor of Ophthalmology at the Medical College of Wisconsin. Both are retinal specialists who perform laser surgery on a regular basis.

I also read the article in the Journal-Sentinel about laser pointers and I decided to be especially careful when using them during lectures. I was greatly relieved when Dr. Connor told me that he knows of no documented reports of permanent damage.

Laser pointers are class 3a, low-power diode lasers that don't exceed safety standards unless a person stares at them continuously for 4-5 seconds. Most people blink at such a bright light within a quarter of a second and turn away. Dr. Connor says that effects on the eye are a combination of light energy and duration, and class 3a lasers are normally not hazardous when viewed momentarily with the naked eye. Class 2a lasers are used in barcode readers, checkout scanners and CD players.

Even for just the eyes, lasers have many applications. According to Dr. Han, lasers are used to reshape the cornea, to improve eyesight, and to treat glaucoma, diabetic retinopathy, and age-related degeneration of the retina. Surgical lasers are probably the safest because facilities with laser instruments are required to have a laser safety officer, and follow strict protocols. After more than a decade of laser use in eye surgery, it appears to be very safe with rare long-term complications.

"Dear Doctor" is a compilation of patient questions answered by doctors from the Medical College of Wisconsin.