Invisible lasers are lasers that essentially operate outside the detection range of the human eye. First, we must understand that UV and IR wavelengths are invisible, lasers designated outside the 400nm ~ 700nm range would be considered undetectable to the human eye. Some IR diodes run at 808nm and 1064nm producing no visible light exposure which creates a potential health hazard if improperly used. Ultraviolet lasers (Invisible lasers) pose the same threat which can be very damaging to cell tissue, eyes and other organic materials.
UV and IR lasers have been fielded in military experiments, research and development, nanotechnology and other sciences. In the end, invisible lasers are merely beams of light our eyes cannot detect. As a result, UV or IR lasers could cause catastrophic damage to the human eye because of no reflex action. Extreme care must be used around lasers that are considered invisible. Lasers of this nature must never be handled by in-experienced enthusiasts.
Another factor in visible lasers such as blue, green, yellow, red laser pointers, are chances of IR leakage in lower quality laser pointers. Latest discoveries have revealed some manufacturers are retailing laser pointers without IR filters as a way to ramp up output and burning capabilities. These pointers affectionately known as "e-Bayzers" in the enthusiast community spew invisible IR, risking serious damage to the eyes. For example; if you're using goggles that accentuate 532nm, they will not stop IR from passing through and causing eye damage. Remember if it's invisible, it can be harmful and lasers are no different.