Laser beam can make you blind, but it is difficult for it to do so. The laser beam that is below 5 mW of light power, for example a standard laser pointer, will damage your vision, for the damage threshold for eyes is about 1 mW. But human eyes will react to the laser beam quickly by blinking and looking away. The time used by a 5 mW laser beam to affect you is longer than the time of blinking. So eyes will be saved by this human safety mechanism. If your eyes stay open and stare at the laser beam when it directly points at you, your vision will be definitely damaged. When the laser beam is above 5 mW, your eyes will be affected before you can blink.
It will be very dangerous for your eyes if you accidentally look at a laser beam especially in a direct way without any protection on your eyes when you are playing with the laser beams. This is because that the laser beams are made up of many powerful rays such as ultraviolet rays or infrared rays, thus containing great amount of energy, which will burn your eyes or do other harm to your eyes. If the condition is serious, you may go blind indeed. Therefore, you had better not play with the laser beams by yourself without any professional protection and instruction.