Lasers are no joke. Unless you're willing to treat your laser with the same care as a handgun, you probably shouldn't own one with more than 5 mW of power.
"A laser’s light is concentrated into a narrow beam. If aimed at a person’s eye from close up, most or all of the light goes through the pupil. The already-concentrated light is further focused by the lens onto a sharp (“diffraction-limited”) dot on the retina.
The power density from a 1 milliwatt laser, focused to a point, is brighter than the equivalent area of the sun’s surface. This can cause a detectable change (injury) to the retina, if the laser stays in one spot for a few seconds. This is why in some countries such as the U.K., laser pointers are limited to 1 milliwatt or less.
Fortunately, people have a “blink reflex” where bright light causes blinking and/or moving out of the light. Because the blink reflex automatically limits the exposure time, lasers with an output less than about 5 milliwatts are generally considered safe for the public to use. In the United States, laser pointers are allowed if they are 5 milliwatts or less. According to the U.S. Food and Drug Administration (FDA), as of April 2012 they have never received a report of eye injury from momentary exposures to laser pointers below 5 milliwatts.
However, deliberate staring at a beam under 5 milliwatts can cause blind spots; this has happened to drunk or stupid people. FDA has heard of injuries caused when a person intentionally stared into the beam for a prolonged period of time.
As laser power further increases, the chance of eye injury increases. Even blinking may not help. Above roughly 10 to 20 milliwatts for visible continuous-wave lasers, even an accidental direct hit on an eye at close range (where all of the beam enters the pupil) could cause retinal damage. If the person was looking straight at the laser, the burn will be in the center of a person’s vision. In extreme cases of eye damage, central vision could be almost fully lost, and the person becomes blind in that eye."
http://www.laserpointersafety.com/laser-hazards_head-eyes/laser-hazards_head-eyes.html
"A laser’s light is concentrated into a narrow beam. If aimed at a person’s eye from close up, most or all of the light goes through the pupil. The already-concentrated light is further focused by the lens onto a sharp (“diffraction-limited”) dot on the retina.
The power density from a 1 milliwatt laser, focused to a point, is brighter than the equivalent area of the sun’s surface. This can cause a detectable change (injury) to the retina, if the laser stays in one spot for a few seconds. This is why in some countries such as the U.K., laser pointers are limited to 1 milliwatt or less.
Fortunately, people have a “blink reflex” where bright light causes blinking and/or moving out of the light. Because the blink reflex automatically limits the exposure time, lasers with an output less than about 5 milliwatts are generally considered safe for the public to use. In the United States, laser pointers are allowed if they are 5 milliwatts or less. According to the U.S. Food and Drug Administration (FDA), as of April 2012 they have never received a report of eye injury from momentary exposures to laser pointers below 5 milliwatts.
However, deliberate staring at a beam under 5 milliwatts can cause blind spots; this has happened to drunk or stupid people. FDA has heard of injuries caused when a person intentionally stared into the beam for a prolonged period of time.
As laser power further increases, the chance of eye injury increases. Even blinking may not help. Above roughly 10 to 20 milliwatts for visible continuous-wave lasers, even an accidental direct hit on an eye at close range (where all of the beam enters the pupil) could cause retinal damage. If the person was looking straight at the laser, the burn will be in the center of a person’s vision. In extreme cases of eye damage, central vision could be almost fully lost, and the person becomes blind in that eye."
http://www.laserpointersafety.com/laser-hazards_head-eyes/laser-hazards_head-eyes.html