A new study by the National Institute of Standards and Technology shows that inexpensive green laser pointers can damage the retina. In a test of several models that were advertised to have a power output of 10 milliwatts, a number of them emitted more infrared light than indicated at levels that are harmful to the eyes. Inexpensive models like those tested lack a filter that can cut down on the unsafe infrared emissions. More expensive devices include this simple filter.
As reported in ScienceDaily.com, “owners of the devices should never point the lasers at the eyes or aim them at surfaces such as windows, which can reflect infrared light back to the user — a particularly subtle hazard because many modern energy-saving windows have coatings designed specifically to reflect infrared.”
Source: NIST