Laser pointer hazard statistics indicated are misleading

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Editor;

(Re: “Stop use of green laser as a toy” Mailbag, Jan. 6) Yes, laser pointers have been misused to cause annoyances in beach towns (Ocean City, NJ, USA) and sporting events. In general, youths should not be permitted to play with them.

However, the hazard statistics indicated are misleading. The Nominal Ocular Hazard Zone of a 5 milliwatt green laser pointer (the most powerful allowed as a pointer in the USA) is 52 feet, not 5 km. And, the NOHD includes a safety factor; at 16 feet there is a 50/50 chance of the smallest medically detectable retinal lesion under optimal conditions where the person does not blink. At 52 feet it is essentially impossible to cause an injury.

It is true that lasers should never be aimed at cars or aircraft. This is more because of the bright light causing temporary flash-blindness or distraction. A 5 milliwatt green pointer can be a distraction to a pilot up to 2.2 miles away. There are many cases in countries worldwide of persons being arrested, fined and jailed for aiming lasers at aircraft.

Yes, the child’s parents were wrong to allow laser misuse. It was rude, could cause eye discomfort, and had a very small chance of causing an injury.

However, the public should not unduly fear eye damage. It is actually very hard for consumer laser pointers to cause eye damage unless a person deliberately stares into them. The number of cases, worldwide, where a consumer laser accidentally injures the eye of a bystander or innocent person is very low – around 2-3 per year. Such injuries are low grade and heal without adverse effect. Only deliberate self-infliction causes more severe eye injuries.

Patrick Murphy

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