There are laser light levels that are considered safe even if light gets directly in to the eyeball. From memory, the safe level is around 1mw, anything greater and permanent damage can occur if the light enters the eye directly, anything less than a total reflection would be unlikeley to cause eye damage, but when I worked on communication equipment with infrared lasers we were taught to assume all laser light was hazardous. Therefore even a 5mw green laser should be used responsibly, but that said it is unlikely that backscattered light presents any danger. Here is a document that outlines possible problems and relevant effects at various powers.
http://www.mech.unsw.edu.au/safety/S...guidelines.pdf