The light show was at Aquamarine Open Air Festival in Kirzhac, near Moscow. So far 29 people have been taken to hospital, with what is severe scarring on their retinas.
Speaking to Kommersant, a local Russian newspaper, an ophthalmologist (eye doctor) at one of the hospitals said: "They all have retinal burns, scarring is visible on them. Loss of vision in individual cases is as high as 80%, and regaining it is already impossible." Ouch!
The laser damage is said to have happened because of the use of outdoor lasers indoors.
Torrential rain meant that the open air festival wasn't actually open air, but in a tent. The reflection of the lasers in the tent hit the crowd instead of the sky and damaged many of the partygoers' vision.