Diode lasers, are very weak these are the types that are used in laser pointers. These lasers typically emit a red beam of light that has a wavelength between 630 nm and 680 nm, you won't exactly loose your eye sight but they can damage the retina.

I found the most lucid explaination here: http://xfelinfo.desy.de/en/artikel.laser-prinzip/2/index.html The image below shows one such common laser device.

Lasers work on the basic principle of coherence. They are light amplified stimulated emitted radiations.When ever a light of particaular wavelenght is made to pass in a coherent manner they are known as lasers.They are amplified version of light of very high intensity.As they are coherrent they focus on any particular point.

Turn the switch on, or press the green on button. Don't forget to plug it in!

A laser pointer works through a relatively simple mechanism, but they are in fact dangerous to your eyes. When the button on the outside of the laser pointer is pressed, electric energy is transferred from the batteries to a compound inside the body of the laser pointer (this substance varies between pointers and can cause different colors). This energy excites electrons in the substance, which soon after entering this excited state fall back into their original orbits around the nucleus. When they fall back into their lower positions, the electrons emit photons with a wavelength that corresponds to a color of visible light. The inside of the lazer pointer is entirely a reflective surface, which forces all photons (or light rays) to bounce ceaselessly around the interior until they escape through a minuscule opening at the other end of the pointer. Because so many photons are leaving in a uniform location, the beam is extremely strong and display in a point, seen when you shine a laser pointer on an object. Staring into a laser is dangerous for your eyes as it as the strength of the light is comparable to staring into the sun and will burn your retina. Hand held laser pointers are relatively weak, but can still damage your eyesight

A laser pointer works on the laser principle. It can be dangerous to your eyesight to look into one. 1) "A laser pointer is a portable, pen-sized laser designed to be held in the hand, and most commonly used to project a point of light to highlight items of interest during a presentation. Most laser pointers have low enough power that the projected beam presents a minimal hazard to eyes for incidental exposure. Consequently, beams from laser pointers are generally not visible from the side in normal clear air, but only visible as a point of light where the beam strikes a diffusely reflective surface. Some higher powered laser pointers are faintly visible via Rayleigh scattering when viewed from the side in moderately to dimly lit conditions." "The output of laser pointers is generally limited by ANSI to 1 mW or 5 mW in order to prevent accidental damage to the retina of human eyes. Usually, pen lasers are class 2 or class 3a lasers, which require extended viewing times to damage the retina severely. "The risk to the human eye from transient exposure to light from commercially available class 3A laser pointers having powers of 1, 2, and 5 mW seems negligible." The Food and Drug Administration (FDA) has determined that Class 3a lasers could cause injury to the eye if viewed directly for approximately 0.25 seconds, although it has cited evidence that exposure to visible lasers is "usually" limited by the blink reflex of the eye, which they have timed at just under 0.25 seconds. In the late 1990s, the laser pointer became a fad amongst adolescents as an irritant to be pointed stealthily at a movie theater screen or even at a person's eyes. In January of 2005, a New Jersey man was arrested for pointing a green laser pointer at a small jet flying overhead. Despite legislation limiting the output of laser pointers in some countries (such as the United States and Australia), higher-power devices are currently produced in other regions (especially China and Hong Kong), and are frequently imported by customers who purchase them directly via internet mail order. The legality of such transactions is not always clear; typically, the lasers are sold as research or OEM devices (which are not subject to the same power restrictions), with a disclaimer that they are not to be used as pointers. DIY videos are also often posted on Internet video sharing sites like YouTube which explain how to make a high-power laser pointer using the diode from an optical disc burner. As the popularity of these hazardous devices soared, many manufacturers (mainly in China) began manufacturing similar high powered pointers. The FDA has published a warning on the dangers of such high powered lasers. Despite the disclaimers, such Lasers are frequently sold in packaging resembling that for laser pointers. Lasers of this type may not include safety features sometimes found on laser modules sold for research purposes." Source and further information: http://en.wikipedia.org/wiki/Laser_pointer Further information: http://en.wikipedia.org/wiki/Laser_safety 2) "A laser is an electronic-optical device that emits coherent light radiation. The term "laser" is an acronym for Light Amplification by Stimulated Emission of Radiation. A typical laser emits light in a narrow, low-divergence monochromatic (single-coloured, if the laser is operating in the visible spectrum), beam with a well-defined wavelength. In this way, laser light is in contrast to a light source such as the incandescent light bulb, which emits light over a wide area and over a wide spectrum of wavelengths." Source and further information: http://en.wikipedia.org/wiki/Laser

any light can damage your eye if too strong. the reason for this is the cells in the back of your eye can be overworked or kill from broght lights, this then stops you from seeing. powerful lasers can also deform the shape of your eye and make things blurd